Weather Sensor
FD12P
USER'S GUIDE
M210296en-A
May 2002
PUBLISHED BY
Vaisala Oyj
P.O. Box 26
FIN-00421 Helsinki
Finland
Phone (int.): +358 9 8949 1
Fax:
+358 9 8949 2227
Visit our Internet pages at http://www.vaisala.com/
© Vaisala 2002
No part of this manual may be reproduced in any form or by any means,
electronic or mechanical (including photocopying), nor may its contents be
communicated to a third party without prior written permission of the copyright
holder.
The contents are subject to change without prior notice.
Please observe that this manual does not create any legally binding obligations for
Vaisala towards the customer or end user. All legally binding commitments and
agreements are included exclusively in the applicable supply contract or
Conditions of Sale.
_________________________________________________________________________________
Table of Contents
CHAPTER 1
GENERAL INFORMATION ..........................................................................11
About This Manual..................................................................11
Contents of This Manual......................................................11
Version Information................................................................12
Related Manuals .....................................................................12
Safety .......................................................................................12
General Safety Considerations............................................12
Product Related Safety Precautions ...................................13
Safety Summary.............................................................13
Ground the Equipment ...................................................13
Radio Frequency Interference Statement (USA) ...........15
ESD Protection ....................................................................15
Trademarks .............................................................................16
Warranty ..................................................................................16
CHAPTER 2
PRODUCT OVERVIEW ................................................................................17
Introduction.............................................................................17
Hardware Structure .............................................................17
Sensing Elements ..........................................................19
Electronics Enclosure .....................................................20
Structural Elements ........................................................20
Operating Principle ..............................................................21
Using FD12P .......................................................................22
Equipment Nomenclature ......................................................23
Specifications .........................................................................24
Mechanical Specifications ...................................................24
Electrical Specifications.......................................................24
Optical Specifications ..........................................................25
Capabilities and Limitations..................................................26
Visibility Measurement Specifications .................................26
Weather Sensing Specifications..........................................26
Environmental Specifications ..............................................27
CHAPTER 3
INSTALLATION ............................................................................................29
Organizing Installation ...........................................................29
Location and Orientation .......................................................30
Grounding and Lightning Protection....................................32
Equipment Grounding..........................................................32
Internal Grounding...............................................................34
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User's Guide _______________________________________________________________________
Grounding for Testing Purposes......................................... 34
Grounding Remote Units and Communication Cable......... 34
Cable Selection ...................................................................... 35
Line Power Cabling............................................................. 35
Communication Cable......................................................... 35
Unloading and Unpacking..................................................... 36
Unpacking Procedure ......................................................... 36
Storage Information ............................................................ 36
Installation Procedures ......................................................... 37
Constructing the Foundation............................................... 37
Mounting When Casting the Pad................................... 38
Mounting to an Existing Surface.................................... 38
Assembling the FD12P ....................................................... 40
Attaching the DTS14B Temperature Sensor to the Mast ... 41
Connecting Cables.............................................................. 43
Basic Wiring................................................................... 43
Communication Cable EMC-shielding........................... 46
Connecting a Background Luminance Sensor or a
Day/Night Switch to FD12P ........................................... 48
Communication Options ..................................................... 50
Serial Communications Settings.................................... 50
Serial Transmission RS-232 .......................................... 50
Serial Multipoint Transmission RS-485 ......................... 51
Modem DMX21.............................................................. 52
Indicators and Manual Controls ..................................... 54
Indicators .................................................................. 54
Manual Controls ....................................................... 54
Analog Transmission ..................................................... 55
Connecting the Maintenance Terminal.......................... 55
Startup Testing.................................................................... 56
Initial Settings...................................................................... 56
CHAPTER 4
OPERATION ................................................................................................ 59
Introduction ............................................................................ 59
User Commands in Normal Operation................................. 59
Markings Used in This Manual ............................................. 61
Entering/Exiting the Command Mode.................................. 61
OPEN Command ................................................................ 61
CLOSE Command .............................................................. 62
Automatic Message Sending ................................................ 62
Message Types................................................................... 63
Message 0 ..................................................................... 64
Message 1 ..................................................................... 64
Message 2 ..................................................................... 65
Message 3 ..................................................................... 65
Message 4 ..................................................................... 66
Messages 5 and 6 ......................................................... 66
Message 7 ..................................................................... 68
Message Polling ..................................................................... 69
FD12P Command Set............................................................. 70
HELP Command ................................................................. 70
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MES Command ...................................................................71
AMES Command............................................................71
Weather Related Commands ..............................................73
WPAR Command ...........................................................73
WSET Command ...........................................................73
Precipitation Limit ......................................................74
Weather Update Delay..............................................74
Haze Limit .................................................................74
Rain Intensity Scale...................................................75
Violent Rain Limit ......................................................75
Heavy Rain Limit .......................................................75
Light Rain Limit..........................................................75
Drizzle Limit...............................................................75
Heavy Drizzle Limit....................................................76
Light Drizzle Limit ......................................................76
Snow Limit.................................................................76
Heavy Snow Limit......................................................76
Light Snow Limit ........................................................76
Snow Pellets Limit .....................................................77
Snow Grains Limit .....................................................77
Ice Crystals Limit .......................................................77
Hail Limit....................................................................77
DRD Scale.................................................................77
Warm Limit ................................................................77
PRW Command..............................................................77
CLRS Command ............................................................78
WHIS Command.............................................................78
System Configuration Commands.......................................79
PAR Command...............................................................79
CONF Command............................................................80
BAUD Command ............................................................84
BLSC Command.............................................................84
Maintenance Commands.....................................................85
STA Command ...............................................................85
CAL Command ...............................................................87
TCAL Command.............................................................87
CLEAN Command..........................................................88
CHEC Command............................................................89
FREQ Command ............................................................89
DRY and WET Commands ............................................89
AN Command .................................................................90
Analog Output Commands ..................................................91
Analog Output Calibration ..............................................91
Data Scaling ...................................................................92
Hardware Check.............................................................92
Other Commands ................................................................93
TIME Command .............................................................93
DATE Command ............................................................93
RESET Command..........................................................94
CHAPTER 5
FUNCTIONAL DESCRIPTION .....................................................................95
General.....................................................................................95
Optical Measurement .............................................................96
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Optical Arrangement ........................................................... 96
FDT12B Transmitter Unit .................................................... 96
FDR12 Receiver Unit .......................................................... 98
Additional Measurements ..................................................... 99
General ............................................................................... 99
DRI21 Interface Board ........................................................ 99
DRD12 Rain Detector ....................................................... 100
DTS14B Temperature Sensor .......................................... 101
FDP12 Control Unit .............................................................. 101
Measurement Signal Processing........................................ 103
Optical Signal Processing................................................. 103
DRD12 Signal Processing ................................................ 104
Algorithm Description ......................................................... 105
Visibility ............................................................................. 105
Detecting Precipitation ...................................................... 106
Precipitation Intensity........................................................ 106
Precipitation Accumulation ............................................... 107
Present Weather ............................................................... 108
Precipitation Types ...................................................... 108
Liquid Precipitation ................................................. 109
Frozen Precipitation................................................ 110
Mixed Precipitation ................................................. 111
Unknown Precipitation............................................ 111
Visibility Types ............................................................. 111
Fog.......................................................................... 111
Haze and Mist......................................................... 112
Weather Classes ......................................................... 112
Weather Code Selection.............................................. 113
Applications.......................................................................... 113
Internal Monitoring .............................................................. 114
Built-in Tests ..................................................................... 114
Memory Tests ................................................................... 115
Signal Monitoring .............................................................. 115
Hardware Monitoring......................................................... 115
Contamination Monitoring................................................. 116
CHAPTER 6
MAINTENANCE ......................................................................................... 117
General.................................................................................. 117
Cleaning ................................................................................ 118
Cleaning Lenses and Hoods............................................. 118
Cleaning DRD12 Rain Detector........................................ 118
Calibration ............................................................................ 119
General ............................................................................. 119
Visibility Calibration........................................................... 119
Calibration Check Procedure....................................... 120
Calibration Procedure .................................................. 123
Calibrating the DTS14B Temperature Sensor............. 124
Removing and Replacing.................................................. 126
Removing and Replacing Optical Units ....................... 126
Removing and Replacing the DRD12 Rain Detector .. 129
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Calibrating FD12P Weather Sensor after Unit
Replacement ................................................................130
CHAPTER 7
TROUBLESHOOTING................................................................................133
Warnings ...............................................................................133
Troubleshooting Examples..................................................133
Message Indicating Warning or Alarm .............................133
Message Missing...............................................................134
Visibility Value is Missing...................................................135
Visibility Value is Continuously Too Good.........................135
Visibility is Constantly Too Low .........................................136
FDP12 Reports Precipitation When There Is None...........136
FD12P Reports Frozen Precipitation during Rain .............136
Have Jumper Settings Been Changed? ............................137
Values for Internal Monitoring.............................................137
Getting Help ..........................................................................140
Return Instructions...............................................................140
APPENDIX A
NWS AND WMO CODES USED IN FD12P ...............................................143
The NWS Codes ....................................................................143
APPENDIX B
JUMPER SETTINGS AND INTERNAL WIRING........................................147
CPU Board .............................................................................149
DC-Regulator.........................................................................149
DRI21 Interface Board ..........................................................149
APPENDIX C
TRANSMITTER AND RECEIVER TEST POINTS .....................................151
INDEX .........................................................................................................153
List of Figures
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
Figure 12
Figure 13
Figure 14
FD12P Weather Sensor Site ....................................................18
DRD12 Rain Detector and DTS14B Temperature Sensor .......19
FD12P Block Diagram ..............................................................21
Recommended Location for the FD12P ...................................31
FD12P Equipment Grounding ..................................................33
Casting a Concrete Foundation................................................37
Constructing the FD12P Foundation ........................................39
Tilting the Pole Mast .................................................................41
DTS14B and the Sensor Holder Assembly to Mast .................42
Connecting Internal Grounding.................................................43
Cabling Principle.......................................................................44
Line Voltage and ON/OFF Switches.........................................45
Electronics Enclosure Feedthroughs........................................46
Cable Grounding Instructions ...................................................47
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Figure 15
Figure 16
Figure 17
Figure 18
Figure 19
Figure 20
Figure 21
Figure 22
Figure 23
Figure 24
Figure 25
Figure 26
Figure 27
Figure 28
Figure 29
Figure 30
Figure 31
Figure 32
Figure 33
Figure 34
Figure 35
Figure 36
Figure 37
Figure 38
Wiring the Connector for the LM11 Background Luminance
Meter ........................................................................................ 49
Wiring the Day/Night Photo Switch .......................................... 50
Communication Option ............................................................ 51
RS-485 Communication Option ............................................... 52
Wiring the Modem .................................................................... 53
Analog Current Loop Option .................................................... 55
FD12P Optical System............................................................. 96
FDT12B Transmitter Block Diagram ........................................ 97
FDR12 Receiver Block Diagram .............................................. 98
DRI21 Block Diagram in the FD12P Application.................... 100
DRD12 Block Diagram........................................................... 101
FDP12 Control Unit Block Diagram ....................................... 102
Optical Raw Data (in Rain) .................................................... 103
Optical Signal Amplitude Distribution (in Rain) ...................... 104
DRD12 Surface Signal (Heavy Rain Beginning).................... 104
Precipitation Type Determination Principle............................ 109
Assembling the FDA13 Calibrator.......................................... 122
DTS14 Sensor Holder Assembly to Mast .............................. 125
Removing the Optical Units ................................................... 127
Replacing the Optical Units.................................................... 128
Removing the DRD12 Rain Detector ..................................... 129
Basic Electronics Enclosure Wiring ....................................... 148
Test Points, Transmitter......................................................... 151
Test Points, Receiver ............................................................. 152
List of Tables
Table 1
Table 2
Table 3
Table 4
Table 5
Table 6
Table 7
Table 8
Table 9
Table 10
Table 11
Table 12
Table 13
Table 14
Table 15
Table 16
Table 17
Table 18
Table 19
8
Manual Revisions..................................................................... 12
Related Manuals ...................................................................... 12
Basic Set .................................................................................. 23
Options..................................................................................... 23
Mains Cable Selection ............................................................. 35
Communication Cable Lengths................................................ 35
Transmit Frequencies of the DMX21 Modem Board ............... 53
LED Indicators of the DMX21 Modem ..................................... 54
Manual Controls of the DMX21 Modem................................... 54
Default Communication Settings.............................................. 57
Commands for Changing the Default Settings ........................ 57
Commands for Displaying and Changing the Parameters ...... 57
Settings and Corresponding Commands................................. 60
Routine Command for Maintenance ........................................ 60
Status Report Command ......................................................... 60
Transmitter Status Correspondence between MITRAS and
FD12P ...................................................................................... 67
Receiver Status Correspondence between MITRAS and FD12P67
HELP Command Sets.............................................................. 70
Commands for Displaying or Setting Weather Analysis
Parameters............................................................................... 73
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Table 20
Table 21
Table 22
Table 23
Table 24
Table 25
Table 26
Table 27
Table 28
Table 29
Table 30
Table 31
Table 32
Table 33
Table 34
Table 35
Table 36
Table 37
Table 38
Table 39
Table 40
Table 41
Table 42
Commands for Displaying System Parameters and Editing the
Current System Configuration ..................................................79
Maintenance Commands..........................................................85
Hardware Error Texts ...............................................................86
Hardware Warning Texts ..........................................................86
Parameters for Optical Measurement.....................................131
Parameters for DRD12 Precipitation Detector .......................131
Parameters for DTS14 Temperature Sensor..........................131
Updating Parameters..............................................................131
Parameters and Commands...................................................132
Values for Internal Monitoring.................................................138
Internal Weather Types, NWS Code .....................................143
WMO SYNOP Codes (4680, W aW a) ......................................143
WMO SYNOP Codes (4680, W aW a) ......................................144
WMO SYNOP Codes (4680, W aW a) ......................................144
WMO Code Table 4678. Codes Used by FD12P...................145
CPU Board Jumpers...............................................................149
CPU Board Connectors ..........................................................149
DC-regulator Connectors........................................................149
DRI21 Interface Board Jumpers .............................................149
DRI21 Interface Board Connectors ........................................150
Electronics Enclosure/Transducer Cable Signals ..................150
Transmitter Test Points...........................................................151
Receiver Test Points...............................................................152
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10 ______________________________________________________
M210296en-A
Chapter 1 _________________________________________________________ General Information
CHAPTER 1
GENERAL INFORMATION
About This Manual
This manual is a general information source as well as a detailed
operational guide to the FD12P Weather Sensor.
Contents of This Manual
This manual consists of the following chapters:
- Chapter 1, General Information, provides important safety, revision
history, contact, and warranty information for the product.
- Chapter 2, Product Overview, introduces the FD12P Weather
Sensor features, advantages, and the product nomenclature.
- Chapter 3, Installation, provides you with information to help you
install this product.
- Chapter 4, Operation, contains information needed to operate this
product.
- Chapter 5, Functional Description, gives a functional description on
the product.
- Chapter 6, Maintenance, describes the overall maintenance of the
product.
- Chapter 7, Troubleshooting, deals with troubleshooting
information.
- Appendix A, NWS and WMO Codes Used in FD12P
- Appendix B, Jumper Settings and Internal Wiring
- Appendix C, Transmitter and Receiver Test Points
VAISALA ________________________________________________________________________ 11
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Version Information
Table 1
Manual Revisions
Manual Code
FD12P-U106en-1.2
M210296en-A
Description
Weather Sensor, User's Guide
This manual.
Related Manuals
Table 2
Related Manuals
Manual Code
DMX21T0496-1.1
LM11T0545-1.2
Manual Name
DMX21 CCITT Modem
LM11 Background Luminance Meter
Safety
General Safety Considerations
Throughout the manual, important safety considerations are
highlighted as follows:
WARNING
Warning alerts you to a serious hazard. If you do not read and follow
instructions very carefully at this point, there is a risk of injury or
even death.
CAUTION
Caution warns you of a potential hazard. If you do not read and
follow instructions carefully at this point, the product could be
damaged or important data could be lost.
NOTE
Note highlights important information on using the product.
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M210296en-A
Chapter 1 _________________________________________________________ General Information
Product Related Safety Precautions
The FD12P Weather Sensor delivered to you has been tested for
safety and approved as shipped from the factory. Note the following
precautions:
WARNING
Ground the product, and verify outdoor installation grounding
periodically to minimize shock hazard.
CAUTION
Do not modify the unit. Improper modification can damage the
product or lead to malfunction.
Safety Summary
The following are general safety precautions must be observed during
all phases of installation, operation and maintenance.
WARNING
Neglecting to follow these precautions or specific warnings and
cautions elsewhere in this manual violates safety standards of design,
manufacture and intended use of the instrument. Vaisala Oyj. and its
Subsidiaries do not answer for the consequences if the customer
neglects to follow these requirements.
Ground the Equipment
To minimize the hazard of electrical shock, follow accurately the
installation procedure in Chapter 3, Installation, on page 29.
NOTE
Note that the chassis of the FD12P Weather Sensor must be
connected to a good electrical earth. The instrument is equipped with
a three-conductor AC power cable. Be sure that the earth wire of the
cable is connected to an electrical ground.
There is also a grounding clamp at the bottom of the electronics
enclosure of Weather Sensor FD12P. Good grounding with a 16-mm2
VAISALA ________________________________________________________________________ 13
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cable must be provided. Besides increasing safety, this also protects
the Weather Sensor against lightning induced voltages.
To prevent operator injury or damage to the Weather Sensor, check
that the LINE VOLTAGE SETTING is correct before connecting the
line power (See Figure 12 on page 45.) Also ensure that the line power
outlet is provided with a protective ground contact.
WARNING
Do not operate in an explosive atmosphere.
Do not operate the equipment in the presence of flammable gases or
fumes. Operation of any electrical instrument in such an environment
constitutes a definite safety hazard.
WARNING
Do not service or adjust alone.
Do not attempt internal service or adjustment unless another person,
capable of rendering first aid and resuscitation, is present.
WARNING
Keep away from live circuits.
Component replacement or internal adjustments must be made by
qualified maintenance personnel. Operating personnel must not
remove instrument covers. Do not remove or replace any components
with the power cable connected. Under certain conditions, dangerous
voltages may exist even with the power cable disconnected. To avoid
injuries disconnect power, and discharge all circuits before touching
them.
WARNING
Do not substitute parts or modify the instrument.
Because of the danger of introducing additional hazards, do not
modify or substitute parts in the instrument. Contact Vaisala or its
authorized representative for repairs to ensure that safety features are
maintained.
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Chapter 1 _________________________________________________________ General Information
CAUTION
The component boards including CMOS microchips should be
transported and stored in conductive packages. Although new CMOS
devices are protected against overvoltage damages caused by static
electric discharge of the operator, careful handling is recommended:
the operator should be properly grounded. Unnecessary handling of
component boards should be avoided.
Radio Frequency Interference Statement (USA)
The United States Federal Communications Commission (in 47 CFR
15.838) has specified that the following notice must be brought to the
attention of users of this kind of a product in the USA:
Federal communications commission radio frequency interference
statement
This equipment generates and uses radio frequency energy and if not
installed and used properly, that is in strict accordance with the
manufacturer's instructions, may cause interference to radio and
television reception. The Weather Sensor is designed to provide
reasonable protection against such interference in an airport
installation. However, there is no guarantee that interference will not
occur in a particular installation. If this equipment causes
interference to radio or television reception, which can be determined
by turning the equipment off and on, the user is encouraged to try to
correct the interference by one or more of the following measures:
- reorient the receiving antenna
- relocate this device with respect to the receiver
- move this device away from the receiver
If necessary, the user should consult the dealer or an experienced
radio/television technician for additional suggestions.
ESD Protection
Electrostatic Discharge (ESD) can cause immediate or latent damage
to electronic circuits. Vaisala products are adequately protected
against ESD for their intended use. However, it is possible to damage
the product by delivering electrostatic discharges when touching,
removing, or inserting any objects inside the equipment housing.
VAISALA ________________________________________________________________________ 15
User's Guide _______________________________________________________________________
To make sure you are not delivering high static voltages yourself, take
the following precautions:
- Handle ESD sensitive components on a properly grounded and
protected ESD workbench. When this is not possible, ground
yourself to the equipment chassis before touching the boards.
Ground yourself with a wrist strap and a resistive connection cord.
When neither of the above is possible, touch a conductive part of
the equipment chassis with your other hand before touching the
boards.
- Always hold the boards by the edges and avoid touching the
component contacts.
Trademarks
Intel® is a registered trademark of the Intel Corporation in the U.S.
and other countries.
Warranty
For certain products Vaisala normally gives a limited one-year
warranty. Please observe that any such warranty may not be valid in
case of damage due to normal wear and tear, exceptional operating
conditions, negligent handling or installation, or unauthorized
modifications. Please see the applicable supply contract or conditions
of sale for details of the warranty for each product.
16 ______________________________________________________
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Chapter 2 ___________________________________________________________Product Overview
CHAPTER 2
PRODUCT OVERVIEW
This chapter introduces the FD12P Weather Sensor features,
advantages, and the product nomenclature.
Introduction
The FD12P Weather Sensor is an intelligent, multi-variable sensor for
automatic weather stations and airport weather observing systems.
The sensor combines the functions of a forward scatter visibility meter
and a present weather sensor. In addition, the sensor can measure the
intensity and amount of both liquid and solid precipitation.
The FD12P can be used to automatically determine the visibility and
precipitation related weather codes in the World Meteorological
Organization (WMO) standard SYNOP and METAR messages. The
sensor can also be employed as an observer's aid in a semi-automatic
weather observing system. The sensor is also suitable for other
weather observing systems providing valuable information, for
example, to road and harbor authorities.
The versatility of the FD12P is achieved with a unique operating
principle. The FD12P measures precipitation water content with a
capacitive device and combines this information with optical scatter
and temperature measurements. These three independent
measurements together provide data sufficient for an accurate
evaluation of current visibility and weather type.
Hardware Structure
The structural basis of the FD12P is the pole mast that supports the
transducer crossarm (FDC115). The crossarm contains the optical
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units, FDT12B Transmitter and FDR12 Receiver. The DRD12 Rain
Detector is fastened to the crossarm. The electronics enclosure with
the main data processing and interface units is mounted to the pole
mast as seen in Figure 1 below.
0201-085
Figure 1
FD12P Weather Sensor Site
The following numbers are related to Figure 1 above:
1
2
3
4
5
=
=
=
=
=
Transducer crossarm
DRD12 Rain Detector
DTS14 Temperature Sensor
Pole mast
Electronics enclosure
The FD12P Weather Sensor consists of three parts: sensing elements,
electronics enclosure, and structural elements. They are described in
detail on the next page.
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Chapter 2 ___________________________________________________________Product Overview
Sensing Elements
The FDT12B Transmitter emits pulses of near infrared light. It is
permanently tilted 16.5º downwards. The optical power is stabilized
by a closed hardware loop. The unit also includes a receiver circuit for
monitoring lens contamination.
The FDR12 Receiver measures the scattered part of the FDT12B light
beam. The FDR12 contains also an additional light transmitter for
monitoring lens contamination. Like the transmitter, the receiver is
also tilted 16.5º downwards. Therefore, the receiver unit measures
light scattered at an angle of 33°.
The DRD12 Rain Detector outputs a signal proportional to the amount
of water on two RainCap™ sensing elements. These elements consist
of thin wires protected by an insulating glass coating. The presence of
water changes the capacitance of the elements. The combined
capacitance of the plates is measured by the DRD12 electronics.
Integrated heating resistors keep the elements dry when, for example,
fog and melt snow fall on them. The Rain Detector is protected by a
windshield to decrease the effect of wind on the measurement results.
The DRD12 is illustrated in Figure 2 below.
The DTS14B Temperature Sensor is a Pt100 thermistor that is used to
measure the crossarm temperature. See Figure 2 below.
0201-086
Figure 2
DRD12 Rain Detector and DTS14B Temperature
Sensor
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The following numbers refer to Figure 2 on page 19:
1
2
3
4
5
=
=
=
=
=
Two RainCapTM elements
DRD12 Rain Detector
Wind shield
Assembly clamp
DTS14 Temperature sensor
Electronics Enclosure
The FDP12 Control Unit is the main data processor and
communication unit of the FD12P.
The DRI21 Interface Board is a Vaisala, general-purpose sensor
interface, with several analog and digital input channels. In the
FD12P, one of the DRI21 Interface Board channels is used for
measuring the crossarm temperature and the DRD12 analog signal. In
addition, the DRI21 controls the DRD12 heating and reads the
precipitation ON/OFF status.
The FDW13 Mains Power Supply converts the mains voltage to
24 VAC power for the FDS12 regulator and the heater elements. The
FDW13 includes also the mains voltage selector and the mains
ON/OFF switch, which also functions as an automatic fuse.
The FDS12 DC Voltage Regulatorconverts the AC or DC input
voltage (min. 18 V) to 12 VDC power used by FD12P electronics. The
FDS12 also includes one relay used to control heater power.
The DMX21 Modem (optional) is a standard, 300-baud modem used
only in the leased line mode with the FD12P.
The FDE12 Backup Temperature Sensor is included.
Structural Elements
The structural elements include the pole mast with a standard height
of 2 meters and the FDC115 Transducer Crossarm with a length of
1.5 meters, which is also the total width of the FD12P.
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Chapter 2 ___________________________________________________________Product Overview
Operating Principle
The FD12P Weather Sensor is a microprocessor controlled, intelligent
sensor combining optical forward scatter measurement, capacitive
precipitation sensing, and temperature measurement. The main units
of the FD12P are shown in Figure 3 below.
9502-091
Figure 3
FD12P Block Diagram
The FD12P evaluates Meteorological Optical Range (MOR) by
measuring the intensity of infrared light scattered at an angle of 33°.
The scatter measurement is converted to the visibility value (MOR)
after a careful analysis of the signal properties. Special processing is
used in case of precipitation.
The FD12P software detects precipitation droplets from rapid changes
in the scatter signal. The droplet data is used to estimate optical
precipitation intensity and amount. In addition to the optical signal,
the analog output of the DRD12 Rain Detector is used to estimate the
precipitation intensity and type.
VAISALA ________________________________________________________________________ 21
User's Guide _______________________________________________________________________
The output of the DRD12 is proportional to the water amount on the
capacitive sensing surfaces while the optical intensity is proportional
to the total volume of the reflecting particles. The ratio of optical and
capacitive intensities is used to determine the basic precipitation type.
The crossarm temperature (TS) is measured with the DTS14B
Temperature Sensor connected to the DRI21 interface card. The
temperature data together with the optical signal profile and the
DRD12 surface sensor data are used to determine the actual weather
code.
The software performs all signal analyses in the FD12P except the
DRD12 Rain ON/OFF status, which is hardware-based and is used as
an auxiliary parameter. The FD12P has a fixed program that is divided
into tasks executed under control of a real-time operating system
kernel. Each task is like an endless loop with a limited function. The
operating system kernel controls the timing of the tasks and the
interactions between the tasks.
Using FD12P
The FD12P is typically used as a component of a weather observing
system. The final weather message (SYNOP, METAR) is then coded
in the central unit of a weather observation system (for example,
Vaisala MILOS 500) or by a human observer using the FD12P as an
observation aid.
The FD12P output is a digital serial interface, which can be
configured into two different operating modes: the sensor can be set to
send a data message automatically at selected intervals, or the FD12P
can be polled by the host computer. The same serial line is also used
as an operator interface.
The operator controls and checks the operation of the FD12P by using
a maintenance terminal. A set of built-in commands and test routines
is provided for configuring and monitoring the multiple functions of
the FD12P.
The standard data messages contain a status character for indicating
faults detected by the internal diagnostics. If the error status is set, the
operator can view a special status message. It contains detailed results
of the diagnostics and a written description of the fault. Using this
information, the operator can take corrective action or provide the
maintenance personnel with valuable advice.
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Chapter 2 ___________________________________________________________Product Overview
Equipment Nomenclature
The standard equipment nomenclature and common names are listed
in Table 3 and Table 4 below.
Table 3
Basic Set
Type
FDC115
Name
Transducer Crossarm
FDT12B
FDR12
16614ZZ
FDB12
Transmitter
Receiver
Crossarm Cable
Electronics Enclosure
FDP12
FDS12
FDW13
DRI21
16615ZZ
16737ZZ
DRD12
FD30513
13145
Processor Board
DC Voltage Regulator
Mains Power Supply
Interface Board
Transducer Cable
I/O Bus Cable
Rain Detector
Pole Mast
Base Plate and
Installation Set
Table 4
Power, conversions, interfacing
assembly
Standard 2-m mast
Options
Type
FDA13
FD45094
Name
Visibility Calibration Set
Maintenance cable
Termbox-48
Mains and Signal
Junction Box
FD12MODEM Modem Option
FD12PLM11 LM11 Option
16616ZZ
Description
Optics, analog, monitoring
assembly
Extended Transducer
Cable
Description
RS232 cable with 9-pin Dconnector.
Adapting/extending the local
cable. Contains heavy-duty
transient protection circuitry.
For remote communication.
For ambient light
measurement.
For optional high-mast
mounting.
VAISALA ________________________________________________________________________ 23
User's Guide _______________________________________________________________________
Specifications
Mechanical Specifications
- Dimensions: 2.3 m × 1.6 m × 0.6 m (H × W × D)
- Weight: 35 kg, excluding the installation plate for the pole
mast
- Mounting: on a concrete foundation with three ∅16-mm
bolts
- Material: anodized aluminum, natural gray
Electrical Specifications
- Mains supply: 115/230 VAC ± 20 %, 45 ... 65 Hz
- Maximum power consumption: 35 W + 100 W defrosting
heaters (in cold weather)
The sensor electronics:
- Lock-in amplifier
- LED power stabilizer
- Contamination monitor
- Lens heater
The control unit:
- Intel 8031 microprocessor
- Program memory, 64 Kbytes
- Read/write memory, 32 Kbytes
Outputs:
- Serial data line may be used either as RS-232 level signals or
interfaced via an optional data modem
- RS-485 (2-wire)
- 4 - 20 mA analog current (sink) output
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Chapter 2 ___________________________________________________________Product Overview
The output data:
- Automatic or polled data message
- Visibility, present weather, precipitation and status data
- Automatic message type and interval is selectable at 15
seconds to n × 15 seconds (n < 18) intervals
The analog visibility output:
- Selectable range and mode (linear or logarithmic)
- Status control bit for remote alarm relay, etc.
- Alarms and warnings (hardware failures, visibility limits)
Optical Specifications
Operating principle:
- Forward scatter at an angle of 33o and capacitive rain sensor.
The light transmitter:
- Light source: near-infrared LED
- Peak wavelength: 875 nm
- Modulation frequency: 2.3 kHz
- Transmitter lens diameter: 71 mm
- Reference photodiode: for light source control
- Backscatter photodiode: for contamination and blockage
measurement
The light receiver:
- Photodiode: PIN 6 DI
- Spectral response: max. responsivity at 850 nm, 0.55 A/W
(in range 550 ... 1050 nm over 0.3 A/W)
- Reception lens diameter: 71 mm
- Backscatter light source: near-infrared LED for
contamination and blockage measurement
VAISALA ________________________________________________________________________ 25
User's Guide _______________________________________________________________________
Capabilities and Limitations
Visibility Measurement
Specifications
Measurement range of Meteorological Optical Range (MOR):
- 10 ... 50 000 m according to a 5 % Contrast Threshold
Definition
Accuracy:
- ± 10 %, range 10 ... 10 000 m
- ± 20 %, range 10 000 ... 50 000 m
Instrument consistency:
- +4%
Update interval:
- 15 seconds
Weather Sensing Specifications
Precipitation detection sensitivity:
- 0.05 mm/h or less, within 10 minutes
Weather type identification:
- 11 different types of precipitation
- Fog (mist) and haze (smoke, sand)
Weather type reporting:
- WMO code table 4680 (with some additions from code table
4677)
- Code letters for precipitation, NWS
- WMO code table 4678 (supported codes are shown in Table
34 on page 145).
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Precipitation intensity measurement:
- Range 0.00 ... 999 mm/h
- Accuracy ± 30 % (range 0.5 ... 20 mm/h, liquid precipitation)
Environmental Specifications
Operating temperature range:
- − 40 ... +55 oC
Operating humidity range:
- Up to 100 % RH
Wind speed:
-
Up to 60 m/s (standard mast)
Sun orientation:
- Direct and reflected sunlight into the light receiver must be
avoided.
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CHAPTER 3
INSTALLATION
This chapter provides you with information to help you install this
product.
NOTE
Before installation, read section Product Related Safety Precautions
on page 13.
Organizing Installation
Before you begin to install the FD12P Weather Sensor, make a plan of
the installation steps. The following is an example of how to organize
the installation process.
1.
Surveying the site:
- Find the most representative measurement site.
- Determine orientation of the Weather Sensor.
2.
Cabling plan is required for the following:
- Grounding cabling layout and cable type.
- Power supply cabling layout and cable type.
- Modem/signal cabling layout and cable type.
3.
Ordering the construction materials and cables.
4.
Digging for cables and foundation.
5.
Casting the concrete:
- Prepare concrete blocks by using a casting mold.
- Cast the fixing bolts in their places at the same time.
VAISALA ________________________________________________________________________ 29
User's Guide _______________________________________________________________________
6.
Installing the base plate and the pole mast:
- Install the base plate with the bolts on the concrete block.
- Level the plate.
- Mount the pole mast on the base plate.
- Mount the junction box to the pole mast (optional). Junction
boxes are available from Vaisala.
7.
Connecting cables:
- Connect the mains and signal cables of the site to the junction
box or have them ready for direct connection to the sensor.
8.
Final installation:
- Install the electronics enclosure and the crossarm of the
FD12P to the pole mast.
- Connect the power and signal cables of the FD12P.
- Connect the modem/signal line to the host computer, display,
etc.
9.
Start-up tests for the system.
Location and Orientation
The main requirements for the location of the FD12P are as follows:
1.
Place the FD12P at a site where the measurements will be
representative of the surrounding weather conditions.
The ideal site has a minimum clearance of 100 meters from all
large buildings and other constructions that generate heat and/or
obstruct precipitation droplets. Also avoid shading of trees as
this may cause changes in the microclimate.
2.
Make sure the site is free of obstacles and reflective surfaces,
which disturb the optical measurements and act as obvious
sources of contamination.
There must not be any obstacles in the line-of-sight of the
transmitter and receiver units (see Figure 4 on page 31). If the
transmitter beam is reflected from obstacles back to the receiver
unit, the sensor will indicate too low MOR values as the
reflected signal cannot be distinguished from the real scatter
signal. Reflections are detected by rotating the sensor crossarm.
They will change depending on the crossarm orientation. Also
the visibility reading will change accordingly.
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The receiver and transmitter optics should not point towards
powerful light sources or, in bright daylight, reflective surfaces
such as snow or sand. The receiver should point north in the
Northern Hemisphere and south in the Southern Hemisphere.
The receiver circuit may become saturated in bright light, and
the built-in diagnostics will indicate a warning. Intense light can
generate false contamination alarms from the transmitter unit.
Bright daylight will also increase the noise level in the receiver.
The transmitter and receiver should face away from any obvious
source of contamination such as spray from passing vehicles.
Dirty lenses will cause the sensor to report too high visibility
values. Excessive contamination is automatically detected by the
sensor.
Harmful reflections are typically avoided if the transmitter beam
is directed towards a surface, which will reflect most of the light
away from the sensor. The distance of 6 meters shown in Figure
4 below is only for guidance; it is not an absolute requirement.
There should be no flashing lights near the sensor. A flashing
light can cause errors in detecting precipitation towards
No obstacles or reflecting surfaces
0110-178
Figure 4
Recommended Location for the FD12P
The following numbers refer to Figure 4 above.
1
2
=
=
Transmitter
Receiver
VAISALA ________________________________________________________________________ 31
User's Guide _______________________________________________________________________
3.
Power supply and communication lines must be available.
When the site for the FD12P is selected, take into consideration
the available power supply and communication lines. This
influences the amount of work and accessories needed and thus,
the actual installation costs.
Grounding and Lightning Protection
Equipment Grounding
Equipment grounding protects the electrical modules of the FD12P,
for example, against lightning and prevents radio frequency
interference. The FD12P equipment is grounded using a jacketed
grounding cable and conductive grounding rod(s).
The FD12P must be grounded by means of the grounding clamp,
which is located under the cable flange (See Figure 5 on page 33). A
16-mm² jacketed grounding cable is connected to the clamp.
Depending on the need, one to four copper-sheathed steel rods are
driven into the ground. If several rods are needed, the alignment from
the foot of the base plate must be radial.
The grounding principles are the following:
- The grounding rod must be isntalled as close to the pole mast
as possible to minimize the length of the grounding cable.
The grounding cable can be also cast inside the concrete base.
- The length of the grounding rod depends on the local
groundwater level. The lower end of the grounding rod must
continuously touch moist soil.
The grounding quality can be checked with a georesistance meter. The
resistance must be less than 10 ohms. This way the lowest possible
resistance is achieved.
The junction box must be also grounded via the grounding cables in
the same way as the electronics enclosure (Figure 5 on page 33). The
junction box is optional.
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0111-001
Figure 5
FD12P Equipment Grounding
The following numbers refer to Figure 5 above:
1
2
3
4
5
6
7
8
=
=
=
=
=
=
=
=
Electronics enclosure
Junction box (optional)
Mains cable
Cable tubing
Grounding rods
Signal cable
16 mm² grounding cables
Grounding clamp
VAISALA ________________________________________________________________________ 33
User's Guide _______________________________________________________________________
Internal Grounding
The electronics enclosure and the bottom plate of the FD12P are
secured by a 1.5-mm², yellow-green ground cable and the crossarm is
grounded through the transducer cable shield. The other parts of the
crossarm are in galvanic contact with each other.
CAUTION
When installing the FD12P, the grounding flat connector must be
plugged to the ground terminal socket, which is located beside the
MIL-connector in the crossarm. See instructions in section
Assembling the FD12P on page 40 and Figure 10 on page 43.
Grounding for Testing Purposes
The FD12P is provided with a two-meter mains cable. The cable has a
grounded plug. The plug must be connected only to an outlet that has
a ground terminal. This grounding is sufficient when the instrument is
used indoors, for example, for testing purposes.
Grounding Remote Units and
Communication Cable
Remote units, such as, the PC data logger, must be grounded and
protected against lightning.
WARNING
A lightning strike through a communication wire can cause a voltage
surge dangerous to life at remote sites if the remote units are not
properly grounded.
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Cable Selection
Line Power Cabling
The FD12P is supplied with a two-meter power cable. If a local
terminal for 115/230 VAC power supply is not available, use an
extended mains cable from the FD12P to the nearest power source.
This cable should be armored and of underground type. The armored
reinforcing acts as a mechanical shield and also provides protection
against lightning. Ground the cable screen at both ends.
The recommended mains wire cross sections are shown in Table 5
below for mains voltage 230 VAC. For 115 VAC, divide the
maximum distances by four.
Table 5
Mains Cable Selection
Maximum
Distance from
Voltage Source
2 km
4 km
8 km
NOTE
One-wire
Cross-section
Area
1.5 mm 2
2.5 mm 2
4.0 mm 2
Nearest
AWG-gauge
No 15 AWG
No 13 AWG
No 11 AWG
Typical Nonarmored Cable
Diameter
10 mm
14 mm
18 mm
Cables with diameters more than 12 mm require a separate junction
box which is also available from Vaisala.
Communication Cable
The FD12P provides the RS-232C, RS-485, CCITT V.21 modem, and
analog transmission interfaces. Consider your needs for
communication before the installation. The communication method
depends on the distance between the computer or display and the
FD12P and the number of the FD12P sensors. Table 6 below describes
the possibilities.
Table 6
Cable Length
< 150 m
< 500 m
> 500 m
Communication Cable Lengths
One FD12P
RS-232
RS-485, modem
Modem
Several FD12Ps on line
RS-485, modem
RS-485, modem
Modem
VAISALA ________________________________________________________________________ 35
User's Guide _______________________________________________________________________
For a modem and RS signal cable, use a screened, 2 × 0.22-mm²
twisted pair cable with a minimum diameter of 5 mm. For details, see
section Communication Options on page 50.
Unloading and Unpacking
The contents of the delivery in question are specified in the packing
list included with the delivery documents. The FD12P equipment is
normally delivered in three cases containing the following parts:
- Crossarm FDC115 containing the optics.
- Electronics enclosure FDB12 with radiation shield.
- Pole mast.
Two persons can easily move the cases from a truck to the installation
site.
NOTE
Handle gently the case containing the optical parts. Do not drop either
end of the case.
Unpacking Procedure
1.
Read the packing list supplied within the delivery documents.
Compare the packing list against the purchase order to make
sure that the shipment is complete.
2.
Open the covers.
3.
In case of any discrepancies or damage, contact the supplier.
4.
Place the packing materials and covers back in the cases and
store them for possible reshipment.
Storage Information
Store the FD12P in its packages in dry conditions, not in the open air.
The storage conditions are as follows:
- Temperature −40 oC ... 70 oC.
- Relative humidity up to 95 %.
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Installation Procedures
Constructing the Foundation
Cast a concrete foundation or use an existing construction that is level
and rigid. The recommended minimum dimensions for the foundation
are illustrated in Figure 6 below. It is easiest to mount the foundation
screws while casting the pad. If the pad was casted earlier, drill three
holes into the concrete for the wedge bolts.
0110-179
Figure 6
Casting a Concrete Foundation
VAISALA ________________________________________________________________________ 37
User's Guide _______________________________________________________________________
The following numbers and letters refer to Figure 6 on page 37:
A
=
1
2
3
4
5
=
=
=
=
=
Watertight plastic for conducting rainwater away
(recommended)
Concrete block
Surface horizontal to ±0.5°
Ground level
Reinforcing steel
Reinforcing steel or use steel mesh 150 × 150 mm
The Installation Set included in the FD12P delivery contains the
required equipment both for mounting when casting the pad and
mounting to an existing surface. Use the triangle shaped template as
an auxiliary device and remove it before mounting the base plate.
Mounting When Casting the Pad
1.
Fasten the three reinforcing plates to the lower end of the
foundation screws with six M16 nuts. See Figure 7 (C, top view)
on page 39.
2.
Fix the template to the upper ends of the foundation screws with
six nuts.
3.
Embed the assembly in the concrete foundation as shown in
Figure 7 on page 39.
4.
After the concrete has set, remove the template.
Mounting to an Existing Surface
1.
Drill three, ∅20-mm holes using the template, minimum depth
65 mm. Refer to Figure 7 on page 39.
2.
Remove the template.
3.
Clean the holes.
4.
Fasten the foundation screws to the wedge bolts by hand.
5.
Protect the tops of the screws with two nuts tightened together.
6.
Then place the wedge bolt and foundation screw combinations
in the holes, wedge bolts down, and hammer the combinations
down.
7.
Tighten the foundation screws as tight as possible.
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0110-180
Figure 7
Constructing the FD12P Foundation
VAISALA ________________________________________________________________________ 39
User's Guide _______________________________________________________________________
The following numbers and letters refer to Figure 7 on page 39:
A
1
2
3
4
5
6
7
B
6
8
9
C
10
11
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
Mounting when casting the pad
A10.5 DIN125, 4 pieces
M10 x 30 DIN933, 4 pieces
A17 DIN125, 3 pieces
M16 DIN934, 3 pieces
Template
Foundation screw M16 x 250, 3 pieces
Base level
Mounting to an existing surface
Foundation screw M16 x 250, 3 pieces
Template
Wedge bolt M16, 3 pieces
Top view
M10, 4 pieces
Baseplate
Assembling the FD12P
1.
Mount the base plate and level it with the six M16 nuts.
2.
Mount the pole mast pedestal and the tilting support on the base
plate with four M10 bolts (Figure 7 on page 39, C, top view).
3.
Attach the electronics enclosure to the pole mast with two
clamps and four M6 Allen screws.
4.
Tilt the mast. See Figure 8 on page 41.
5.
Feed the crossarm cable and temperature sensor DTS14B cables
inside the pole mast.
6.
Check that a thin rubber gasket is on the insertion neck of the
crossarm.
7.
Connect the crossarm cable plug to the MIL-connector (see
Figure 10 on page 43).
8.
Connect the grounding flat connector to the other pin of the
ground terminal socket as shown in Figure 10 on page 43.
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0110-181
Figure 8
Tilting the Pole Mast
The following numbers refer to Figure 8 above:
1
=
2
=
Pole mast. For tilting, loosen the upper and remove the lower
M10 × 100 bolts.
Tilting supporters. To be installed under the fastening screws.
Attaching the DTS14B Temperature
Sensor to the Mast
To attach the DTS14B Temperature Sensor to the mast, do the
following:
1.
Pull the DTS14B temperature sensor out of the side hole of the
mast.
2.
Then attach the holder to the mast in the following way:
- Open the fixing screw fully (part 3 below).
- Push the screw head to the holder with you finger.
- Put the holder to the hole in the mast pole.
- Slide the holder upwards as long as it goes and hold it there.
- Tighten the fixing screw firmly.
VAISALA ________________________________________________________________________ 41
User's Guide _______________________________________________________________________
- Insert the crossarm to the pole mast and lock it in the right
position with two 8-mm bolts.
- Erect the mast.
- Lift the DRD12 Rain Detector to an upright position. Tighten
the clamp.
0201-088
Figure 9
DTS14B and the Sensor Holder Assembly to Mast
The following numbers refer to Figure 9 above:
1
2
3
=
=
=
Sensor holder
DTS14
Fixing screw
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0110-182
Figure 10
Connecting Internal Grounding
The following numbers refer to Figure 10 above:
1
2
3
4
5
=
=
=
=
=
Crossarm
Ground terminal socket
Grounding flat connector
Pole mast
MIL-connector
Connecting Cables
Basic Wiring
To do the basic wiring, do the following:
1.
The electronics enclosure includes a power cable. Remove the
plug.
VAISALA ________________________________________________________________________ 43
User's Guide _______________________________________________________________________
If you use another, longer cable, make sure to connect the wires
in a correct way, especially the protective ground wire (usually
yellow-green). Refer to Figure 11 below.
2.
Connect the power cord to the screw terminals in a junction box
or bring the power line directly to the electronics enclosure. The
selected method depends on the thickness of the power cable,
which should be checked before the installation. The electronics
enclosure has a cable outlet with a diameter of 10 - 12 mm.
3.
Feed Neutral N (normally blue) and protective earth PE
(normally yellow-green) via separate conductors.
4.
Feed the communication cable through one of the two cable
feedthroughs. For cable shield connections, see instructions in
section Communication Cable EMC-shielding on page 46.
5.
Wire the communication cable according to instructions in
section Communication Options on page 50.
9509-011
Figure 11
Cabling Principle
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NOTE
If the line voltage used differs from 230 V (the initial setting at the
factory), check the voltage setting of the FDW13 Mains Power
Supply (alternatives 115 VAC and 230 VAC). You can find the line
voltage setting switch on the left side of the FDW13 unit (see Figure
12 below).
0110-183
Figure 12
Line Voltage and ON/OFF Switches
The following numbers are related to Figure 12 above:
1
2
3
4
5
6
7
=
=
=
=
=
=
=
Electronics enclosure
Pole mast
DMX21 modem
DC regulator FDW13
ON/OFF switch
Line voltage setting
FD12P control unit
VAISALA ________________________________________________________________________ 45
User's Guide _______________________________________________________________________
0110-184
Figure 13
Electronics Enclosure Feedthroughs
The following numbers refer to Figure 13 above:
1
2
3
4
=
=
=
=
5
6
7
=
=
=
Grounding
DTS14 cable feedthrough
Temperature sensor (TE)
Cap (Pg 13.5) of optional opening for the LM11
background luminance meter
Main power cable
FDC115 transducer cable feedthrough
Standard communication cable feedthrough
Communication Cable EMC-shielding
The electronics enclosure has one cable outlet for a cable diameter
from Ø7 to Ø10 mm, which is reserved for a signal or modem cable.
Although the shielding of the cable may be just grounded after cable
inlet, an efficient procedure against RF-interference requires special
care. Ground the cable gland to keep EMI levels within specifications.
For a proper RF-grounding of any jacketed cable, the instructions are
the following:
1.
Lead the signal cable through the cable inlet. If the field cable is
thicker than 10 mm, use a separate signal junction box. See
Figure 14 on page 47.
2.
Strip 80 mm of the cable sheath leaving approximately 40 mm
of the shield.
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3.
Remove the cap of the cable gland, including the rubber cylinder
and the metal rings. Slide the cap with rubber cylinder onto the
cable.
4.
For a thin cable, add a shrinkable tube to increase cable
diameter.
5.
Slide two metal rings on the shielding and squeeze it evenly
between the rings.
6.
Secure with a shrinkable tube.
7.
Tighten the cable with the cable gland and proceed with the
wiring.
8.
Connect the signal cable to the screw terminals in the electronics
enclosure.
9.
Ground the signal cable with the same method at both ends.
0205-006
Figure 14
Cable Grounding Instructions
VAISALA ________________________________________________________________________ 47
User's Guide _______________________________________________________________________
Connecting a Background Luminance Sensor or a
Day/Night Switch to FD12P
The FD12P Weather Sensor supports two different methods for
ambient light sensing. The Background Luminance Meter LM11 can
be connected to the FD12P for accurate ambient light measurement.
The LM11 sensor and necessary wiring are included in option
FD12PLM11 (see Figure 15 on page 49 for the wiring details). The
background luminance measurement is typically used in the RVR
systems.
The LM11 output frequency is measured with the DRI21 interface
board and then converted into background luminance by the FD12P
software. The conversion uses a scaling factor, which needs to be
configured by the user. For details, see section BLSC Command on
page 84.
In certain applications it is necessary to calculate night visibility
separately using a formula that differs from MOR. In these cases a
simple day/night photo switch is sufficient for discerning between day
and night ambient light conditions. The switch can be connected to the
serial line control input on the FDP12 processor board. For wiring
details, see Figure 16 on page 50.
Positive voltage is interpreted as a night condition and the background
luminance value in the FD12P output message is set to 0. Negative
voltage or an open circuit is interpreted as a day condition and the
luminance value is set to 1. For details, see section BLSC Command
on page 84.
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9610-006
Figure 15
Wiring the Connector for the LM11 Background
Luminance Meter
VAISALA ________________________________________________________________________ 49
User's Guide _______________________________________________________________________
9610-007
Figure 16
Wiring the Day/Night Photo Switch
Communication Options
Serial Communications Settings
NOTE
The factory default settings of the FD12P serial communications port
are 300 baud. Even parity is 7 data bits, 1 stop bit.
Serial Transmission RS-232
For the RS-232 communication, connect the signal wires to screw
terminal X18 (CTR lines not needed) at CPU board FDP12. See
Figure 17 on page 51.
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9509-013
Figure 17
Communication Option
The Vaisala recommendation for the maximum length of the RS-232
cable is 150 m (500 ft).
Serial Multipoint Transmission RS-485
The RS-485 transmission standard allows several FD12Ps to
communicate (half duplex) with the host computer using a single
twisted pair. For the RS-485 communication, connect the signal wires
to 4-pin screw connector X21 at the CPU board. See Figure 18 on
page 52.
In the multidrop configuration, where several FD12P Weather Sensors
are on the same communication line, units are differentiated by an ID.
Set a different unit ID to each FD12P with the CONF command. Set
FD12 P to the polling mode with the AMES 0 2 command. The host
system must ask data messages by polling each FD12P.
VAISALA ________________________________________________________________________ 51
User's Guide _______________________________________________________________________
9509-014
Figure 18
RS-485 Communication Option
Modem DMX21
The Modem DMX21 is a CCITT V.21 modem, operating at 300 bps.
Connect the signal wires to MODEM LINE 1 and 2, and screw
terminals 7 and 9 on Interface board 16127FD. See the wiring diagram
in Figure 19 on page 53.
In the multidrop configuration, where several FD12P Weather Sensors
are on the same modem line, the units are differentiated by an ID. Set
a different unit ID to each FD12P with the CONF command. In the
multidrop configuration, only one FD12P modem carrier can be active
at the time. To set the modem carrier under the FD12P software
control, set jumper X2 to position 1-3 in the modem interface board as
shown in Figure 19 on page 53. If the X2 jumper is in position 3-4 and
if the unit ID is not set, FD12P keeps the modem carrier signal on all
the time. Set the FD12P to the polling mode with the AMES 0 2
command. The host system must ask data messages by polling each
FD12P.
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9509-012
Figure 19
Wiring the Modem
Usually, the modem of the FD12P operates in the answer mode, and
the modem of the host computer in the originate mode. In the standard
FD12P system, the S3 switch on the DMX21 board is in the DOWN
position and the answer mode is selected. When the switch is in the
UP position, the originate mode is selected. The transit frequencies of
the DMX21 modem are presented in Table 7 below.
Table 7
TXD
CCITT
Transmit Frequencies of the DMX21 Modem Board
Originate Mode
0
1
1180
980
Answer Mode
0
1850
1
1650
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User's Guide _______________________________________________________________________
Indicators and Manual Controls
This section describes the alternatives of the indicators and manual
controls available in the FD12P DMX21 modem.
Indicators
The LED indicators of the DMX21 modem are listed and described in
Table 8 below.
Table 8
LED Indicators of the DMX21 Modem
LED Indicator
LED V16 R
LED V17 ON LINE
LeV18 CD
LED V19 TxD
LED V20 RxD
Description
Ring indicator, normally off.
Normally lit when the S2 switch is in the UP position.
The line, however, is permanently connected by
jumper connections. The V17 LED may also be off
although the modem is online. The S2 switch in the
DOWN position switches the V17 LED off.
Indicates when a carrier frequency is detected. To
make date interchange possible, the modems must
first detect the carrier frequency.
Transmitted data stream when the data is 1, the LED
is lit.
Received data stream. When the received data is 1,
the LED is lit.
Manual Controls
The manual controls and their positions are listed and described in
Table 9 below.
Table 9
Control
S2
S1
S3
Manual Controls of the DMX21 Modem
Position
UP
MIDDLE
DOWN
UP
MIDDLE
DOWN
UP
MIDDLE
DOWN
Description
Line relay permanently on (recommended
position).
Line relay controlled by software (switched lines).
Line relay permanently off.
Software-readable switch (recommended
position).
ORIG mode permanently on.
ORIG/ANSWER modes under software control.
ANSWER mode permanently on (normally
used).¹
¹ The ORIG mode may also be used depending on the host computer modem. When they
operate in the ORIGINATE mode, the modem of FD12 P should be set in the ANSWER
mode and vice versa.
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Analog Transmission
For 4-20 mA analog visibility measurement only two wires are
needed. Do the following:
1.
Connect the voltage supply either from remote or internal supply
(from +Vb = 12 V or +Vbb = 23 V) to resistor R (for example,
100 ohm).
2.
Connect the signal wire to screw connector X20 pin 3 "sink" at
the CPU board. In the drawing, a remote voltage supply is used
and the return signal is wired from pin 4 "gnd". See Figure 20
below.
For more information of the analog output port functioning and
configuring, see section Analog Output Commands on page 91.
9607-007
Figure 20
Analog Current Loop Option
Connecting the Maintenance Terminal
Any computer equipped with a terminal emulation software or a
VT100 compatible terminal with the RS-232 serial interface can be
used as a maintenance terminal for the FD12P. The optional
maintenance cable provides a 9-pin D-connector for the computer and
a 3-pin connector for the FD12P.
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User's Guide _______________________________________________________________________
To connect the maintenance terminal, do the following:
1.
Disconnect the serial line screw connector or modem interfacing
cable (or the RS-485) from X18.
2.
Plug the maintenance cable into X18.
3.
Refer to Figure 17 on page 51 (RS-232).
Startup Testing
Before closing the cover of the electronics enclosure, a short startup
must be done as follows:
1.
Connect a terminal via serial line to the sensor (See sections
Serial Transmission RS-232 on page 50 or Connecting the
Maintenance Terminal on page 55). Set the terminal baud rate to
300 and set the data frame to contain 7 data bits and 1 stop bit,
even parity.
2.
Turn on the main switch at the power supply FDW13.
3.
Check that the red LED on the CPU board is lit for a few
seconds, after which the green LED should start blinking. If not,
continue with troubleshooting.
4.
After startup, the FD12P outputs:
VAISALA FD 12P V1.XX 19YY-MM-DD SN
(ID is also included, if configured.)
5.
Wait for one minute and enter the command mode with the
OPEN command. Check with the STA command that no
hardware errors or warnings are detected.
6.
Enter the automatic message mode by typing CLOSE and check
that a message appears every 15 seconds in the display.
Initial Settings
The FD12P Weather Sensor is typically interfaced to a host computer
or a data logger in an automatic weather observing system. After the
physical connection has been made, the communication details can be
configured in the FD12P software. Suitable communication settings
depend on the implementation of the whole system.
By default the sensor transmits a new ASCII data message through the
serial line every 15 seconds. The user can change the interval and
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message type. The sensor can also be used in a polled mode, that is, a
data message is only sent when the host computer requests one with a
special command. In addition, the baud rate of the serial line can be
changed to a higher value. The default communications settings are
listed in Table 10 below.
Table 10
Default Communication Settings
Setting
Baud rate
Polled or automatic mode,
message type
Sensor ID
Default
300 baud (7E1)
Automatic mode, message 2
interval 15
No ID set
In multipoint communication where several sensors share the same
communication line, the FD12P should be used in the polled mode
and individual sensors must have distinct identifiers (ID).
The baud rate should not be changed if the optional 300-baud modem
is used.
The commands for changing the default settings are listed in Table 11
below. Detailed descriptions of the commands can be found in
Chapter 4 on page 59.
Table 11
Commands for Changing the Default Settings
Operation
Command
Baud rate selection
BAUD
Polled or automatic mode, message type setting AMES
Sensor ID configuration
CONF
The FD12P has also several changeable parameters, which control the
operation of the present weather algorithm and precipitation
measurement. The factory set parameter values have been found
appropriate in tests and usually do not need to be changed. However,
there may be conditions where other parameter values give better
results.
The commands for displaying and changing the parameters are listed
in Table 12 below.
Table 12
Commands for Displaying and Changing the
Parameters
Operation
Parameter listing
Parameter change
Command
WPAR
WSET
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User's Guide _______________________________________________________________________
Local practice may require changes, especially in the precipitation
intensity limits and the haze threshold value. For details, see the
description of the WSET command in section WSET Command on
page 73.
When the precipitation intensity and amount measurement is not
factory calibrated, higher accuracy can be achieved by adjusting a
scaling factor with the WSET command. The new scaling factor can
be calculated by comparing the FD12P against a reference rain gauge.
For details, see the description of the WSET command in section
WSET Command on page 73.
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CHAPTER 4
OPERATION
This chapter contains information needed to operate this product.
Introduction
The FD12P Weather Sensor is a fully automatic instrument for
continuous weather measurement. Normally, the FD12P Weather
Sensor is either set to send a data message automatically or it is polled
by a host computer. In addition, a set of user commands is provided
for configuring and monitoring the system performance. These
commands can be given in the command mode. See section
Entering/Exiting the Command Mode on page 61.
The FD12P Weather Sensor has seven different standard message
formats for data message output. The FD12P presents the weather
type using the World Meteorological Organization (WMO) code table
4680 (WaWa Present Weather reported from an automatic weather
station). Code numbers 77 (snow grains), 78 (ice crystals), and 89
(hail) are from the code table 4677 because the types are not included
in the code table 4680. In addition, the United States National
Weather Service (NWS) abbreviations are available. The list of NWS
and WMO codes is presented in Appendix A on page 143.
User Commands in Normal Operation
User intervention is not required in the normal operation of the FD12P
Weather Sensor. Operator commands are used only in the initial setup and during routine maintenance. Several commands are also
available for troubleshooting.
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User's Guide _______________________________________________________________________
When the sensor has been installed, the user may need to change some
of the default settings. For details, see section Initial Settings on page
56.
Table 13 below lists the settings and the corresponding commands.
Table 13
Settings and Corresponding Commands
Operation
Baud rate
Polled or automatic mode, message type
setting
Sensor ID
Weather algorithm parameters
Command
BAUD
AMES
CONF
WSET
Table 14 below lists the routine maintenance commands.
Table 14
Routine Command for Maintenance
Operation
Sensor cleaning
Visibility calibration
Temperature calibration
Weather algorithm parameters
Command
CLEAN
(optional)
CHEC, CAL
FREQ, TCAL
WSET
The standard output messages contain a status character, which
presents the results of the internal diagnostics to the host computer or
the user. If the sensor indicates a warning or an alarm in a standard
output message, the host computer or the user can obtain a detailed
status report by using a special command (STA). The status report can
also be polled (message 3) in place of the standard data message.
Usually, the detailed status information is sufficient for locating the
fault.
Table 15 below lists the status report command.
Table 15
Status Report Command
Operation
Getting a status report
Command
STA
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Markings Used in This Manual
The general format of the command is the following:
COMMAND parl...parn ↵
where
Command
parl...parn
↵
NOTE
= An FD12P command given by the user
= Possible parameters of the command
= Symbolizes pressing the ENTER key
All the command parameters are separated from each other by a
space character. Every user command must be ended with ENTER,
illustrated in this manual by ↵.
The system output is illustrated as Courier type font, for example,
BACKSCATTER INCREASED
Entering/Exiting the Command Mode
Before any commands can be given to the FD12P, the communication
line in the FD12P has to be assigned to the operator. Otherwise, it is
assigned to automatic messages or polled communication. The user
assigns the command mode with the OPEN command.
OPEN Command
If no device identifier (id) is defined, type
OPEN ↵
If id is defined, for example as A, type
OPEN A ↵.
If id is defined but forgotten, type
OPEN ^C
↵
where ^ is the control key.
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The FD12P answers
LINE OPENED FOR OPERATOR COMMANDS
If no input is given within 60 seconds, the FD12P closes the line
automatically.
CLOSE Command
Line can be released to automatic data messages by typing
CLOSE
↵
The FD12P answers
LINE CLOSED
Automatic Message Sending
In the automatic (CLOSEd) mode, the FD12P sends the predefined
message at selected intervals. The automatic message is selected by
the AMES command.
AMES Message_number Message_interval ↵
where
Message_number
- The valid range is 0 ... 7, refers to section Message Types on
page 63.
- Selects the corresponding message. Any negative message
number is converted to 0.
- If only the message number is given, the previous message
interval setting is used.
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Message_interval
- Given in multiples of 15 seconds (= measuring interval).
Therefore, intervals 15, 30, 45 ... are valid. Other intervals
are converted to multiples of 15 seconds. The maximum
sending interval is 255 seconds (4 minutes 15 seconds).
For example, typing
AMES 1 60
↵
selects message number 1 to be sent once in a minute.
Messages can also be displayed in the command mode with the MES
command, described in section MES Command on page 71.
Message Types
All the data messages are of fixed length and the data is in fixed
fields. Message 2 is intended to be used as the standard present
weather message. The length of the status message depends on the
possible alarm and warning states.
The FD12P adds frame strings to the polled and automatic messages.
The content of the frame strings is presented in the following:
!FD id"message body#-*
where
!
FD
id
"
#
-*
= Start of heading (ASCII 1, non-printable character, in
terminal screen typically seen as the □ mark)
= FD12P sensor identifier
= Space character
= Unit identifier 2 characters, if ID is not defined
characters space and 1 are shown
= Start of text (ASCII 2, non-printable character)
= End of text (ASCII 3, non-printable character)
= CR + LF (ASCII 13 + ASCII 10)
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User's Guide _______________________________________________________________________
NOTE
The contents of messages 0, 1, 2, 5, 6, and 7 are illustrated as follows:
10
6800
↓↓
↓
<- The first row is the output.
110.96
↓
--------- offset frequency
ì Field
------- one minute average visibility
ídescriptions
- 1=hardware error, 2= hardware warning î
- 1= alarm 1 2= alarm 2
Example with frames
□FD
1□10
6800
110.96□
!FD 1"10
6800 110.96#-*
012345678901234567890123456
NUMBERS mark the character positions.
Message 0
Message 0 displays only the one-minute average visibility truncated to
19900 and the offset frequency of the optical measurement hardware.
00
6800
126.87
------- offset frequency
------- one minute average visibility
- 1=hardware error, 2= hardware warning
- 1= visibility alarm 1, 2= visibility alarm 2
An example with frames is as follows:
□FD
1□00
6800
126.87□
!FD 1"00
6800 126.87#-*
012345678901234567890123456
Message 1
Message 1 displays the instant precipitation type and the optical
(volume) intensity. The intensity can be integrated to rain sum, but not
snow.
00
6839 52
0.3
------ precipitation (volume) intensity, mm/h
--- instant precipitation type, 0 ... 99
------- visibility one minute average, max 50000m
- 1=hardware error, 2= hardware warning
- 1= visibility alarm 1, 2= visibility alarm 2
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An example with frames is as follows:
FD
1 00
6839 52
0.3
!FD 1"00
6839 52
0.3#-*
0123456789012345678901234567
Message 2
Message 2 is intended as the standard present weather message used
in data loggers or display units and it is set as default at the factory.
00
6839
7505
L
52 61 61
0.33
12.16
0
-----cumulative snow
sum,0...999mm
------- cumulative water
sum,0...999mm
------- precipitation (volume)
intensity,mm/h
--- one hour present weather code, 0...99
--- 15 minute present weather code, 0...99
--- instant present weather code, 0 ... 99
---- instant present weather, NWS codes
------ visibility ten minute average, max 50000m
------ visibility one minute average, max 50000m
- 1=hardware error, 2= hardware warning
- 1= visibility alarm 1, 2= visibility alarm 2
An example with frames is as follows:
FD
1 00
6839
7505
L
52 61 61
0.33
12.16
0
!FD 1"00 6839 7505 L 52 61 61
0.33 12.16
0#-*
01234567890123456789012345678901234567890123456789012345
Message 3
Message 3 is the same as the status message obtained by using the
STA command. Refer to Table 22 on page 86 for possible error texts.
FD12P STATUS
SIGNAL
0.39 OFFSET
126.83 DRIFT
REC. BACKSCATTER
1281 CHANGE
-1
TR. BACKSCATTER
10.3 CHANGE
0.1
TE
2.7 VBB
19.4 VH
0.6
LEDI
5.6
P15
15.1 M15
-15.0 BGND
-0.1
AMBL
0.1 DUTY
1.6
DRI21 MEASUREMENTS
TS
1.8 DRD INST
811 DRY
915.6
HARDWARE :
OK
0.14
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Message 4
Message 4 is for hardware monitoring. The same data line is obtained
by using the FREQ command.
0.51
126.82 0.91
15
3
5
2.7
5.6
1280 19.5
1.8
>FREQ
SIGNAL+ OFFSET DIST SWID MAXI OWID TE LEDI BACKS VBB
TS
0.59 126.83 0.91 17
2
6
2.7
5.6 1280 19.4
1.8
0.59 126.83 0.91 17
2
6
2.7
5.6 1280 19.4
817
819
DRD
816
1.8
Messages 5 and 6
Messages 5 and 6 are for MITRAS transmissometer message
emulation in VAISALA RVR systems.
An example of MES 5 is provided below:
"ID 1 V
-*#
--- <CR><LF><ETX>
-- receiver 2 status
(two spaces)
-- receiver 1 status
-- transmitter status
-- S, status heading
------ background luminance value
cd/m2(option)
-- B, background luminance heading
------- (contamination) compensated visibility
(reserved, not supported by FD12P)
--- CV, compensated visibility heading
------- non-compensated visibility m
-- V, visibility heading
-- unit ID (one character only)
-- ID, start indicator
- <STX>
1050 CV ////// B ///// S0101
"ID 1 V
1050 CV ////// B ///// S0101 -*#
1234567890123456789012345678901234567890123
An example of MES 6 is provided below:
"ID 1 V
-*#
--- <CR><LF><ETX>
-- receiver 2 status
-- receiver 1 status
-- transmitter status
-- S, status heading
------ background luminance value cd/m 2
-- B, background luminance heading
------- non-compensated visibility m
-- V, visibility heading
-- unit ID (one character only)
-- ID, start indicator
- <STX>
4550 B ///// S4101
"ID 1 V
4550 B ///// S4101 -*#
123456789012345678901234567890123
The status is in hexadecimal notation.
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The status bits emulate the MITRAS status as shown in Table 16 and
Table 17 below.
Table 16
Transmitter Status Correspondence between
MITRAS and FD12P
BIT
0
1
2
3
4
5
6
MITRAS
MEAS MODE
ECON MODE
OPTICAL SURFACE
POWER SUPPLY
HEATING
FLASH LAMP
BL METER
7
MEASUREM. LOOP SIGNAL
Table 17
Receiver Status Correspondence between
MITRAS and FD12P
BIT
0
1
2
MITRAS
MEAS MODE
SPARE
OPTICAL SURFACE
3
4
POWER SUPPLY
HEATING
OK = OFF
CALIBRATION
TEST
OK = OFF
SPARE
5
6
7
FD12P
ON
OFF
TRB warning or alarm
VBB (power supply)
VH (lens heater current)
LEDI (LED intensity control)
BL meter interface (DRI21)
connected
-
FD12P
ON
REC. BACKSCATTER
warning or alarm
±15 V status
AMBL
The MITRAS polling command is the following:
P<sp><ID><cr><lf>
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Message 7
Message 7 is meant mainly for aviation specific purposes. The
message contents are as follows:
00
23.4 12345
------background
luminance cd/m2
------ surface temperature
----- cumulative snow sum
------- cumulative water sum
------- precipitation water intensity,mm/h
(1 minute average)
--- one hour present weather code, 0 ... 99
--- 15 minute present weather code, 0 ... 99
--- instant present weather code, 0 ... 99
---- instant present weather, NWS codes
------ visibility ten minute average, max 50000m
------ visibility one minute average, max 50000m
- 1=hardware error, 2= hardware warning
- 1= visibility alarm 1, 2= visibility alarm 2
-RA
6839
7505
L
52 61 61
0.33
12.16
0
, instant METAR weather codes
RERA , recent METAR weather (RE criteria used)
An example with frames is as follows:
FD 1 00
-RA
RERA
6839
7505
R
61 61 61
0.33
12.16
0
23.4 /////
!FD 1"00
-RA-*
RERA-*
#-*
6839
7505
R
61 61 61
0.33
12.16
0
23.4 /////-*
Message 7 consists of four lines. METAR present weather codes are
output on the second and third lines. These lines are not of fixed
length because METAR codes can be combined in many ways. The
METAR codes may also be left out but the lines of the message are
always terminated by a carriage return and line feed characters.
The background luminance value displays the measured luminance in
cd/m², if the Vaisala LM11 Background Luminance Meter is attached
to the FD12P (option FD12PLM11). If a day/night switch is
connected to the processor board, the background luminance value
displays the switch state (1 = day, 0 = night).
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Message Polling
In the polled (CLOSEd) mode, the FD12P sends a data message when
the host computer transmits a polling command. The message polling
mode is selected by the following command:
AMES Message_number Message_interval ↵
where
Message_number
- The valid range is 0 ... 7, refer to section Message Types on
page 63.
- Selects the corresponding message as the default polled
message. Any negative message number is converted to 0.
Message_interval
- Negative or zero interval is used to disable the automatic
sending. This is used when messages are polled.
For example, AMES 0 0 ↵ selects message 0, and cancels the
automatic sending.
The polling command format is the following:
<ENQ> FD <SP> id <SP> message_number <CR>
where
<ENQ>
<SP>
id
message_
number
=
=
=
=
ASCII character 05 hex
ASCII character 20 hex (space)
Selected in the configuration
Optional
If only one FD12P unit in on the line and no id is set, the command
format is the following:
<ENQ> FD <CR>
When the FD12P unit number two (id = 2) is polled for message
number 3, the command format is the following:
<ENQ> FD
<SP> 2 <SP> 3 <CR>
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User's Guide _______________________________________________________________________
This format is also used when several devices are on the same line.
Use character 1 as the id if the id has not been set but a specific
message type is polled.
The FD12P does not echo the polling character string.
The answer message format is the following:
<SOH> FD <SP> id <STX> text <ETX><CR><LF>
The id field always contains two characters. If only one character has
been set as the id, the sensor will output an <SP> as the first character
in the field.
When there are several devices on the same line, the polled unit turns
the modem (DMX21) carrier on after it has acknowledged the request.
When the carrier is switched on, additional characters will appear
before the <SOH> (01 hex) character. The FD12P waits about 100 ms
after turning the carrier on before it starts to send the message. When
the FD12P has sent the message, it turns the carrier off. This will also
generate additional characters, which have to be ignored by the host.
FD12P Command Set
HELP Command
The operator receives information about available commands by
typing
HELP
↵
The HELP command sets are listed in Table 18 below.
Table 18
HELP Command Sets
Command
OPEN
CLOSE
MES
AMES Number Interval
STA
PAR
WPAR
PRW
CONF Password
CLEAN
Description
Assigns the line for operator commands
Releases the line for automatic messages
Displays data message
Automatic message
(with parameters Number and Interval)
Displays status
Parameter message
Weather parameter message
Present weather message
Updates configuration
Sets clean references
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Command
CHEC
CAL Calibrator_frequency
CLRS
ACAL
TIME hh mm ss
DATE yyyy mm dd
BAUD rate par
AN channel
DAC data
RESET
WHIS
WSET
DRY ON
WET ON
BLSC
Description
Displays average signal
Calibration
Clears precipitation sums
Analog output calibration
Sets/displays system time
Sets/displays system date
Baud rate setting
(Rate 300, 1200, 4800, 9600)
(Par E(7E1) or N(8N1)
Analog channel
(0,1,3,8 ... 15 or ANALOG ID)
(Without DATA = SWEEP)
Hardware reset by watchdog
Present weather history
PRW reference values
Sets DRD dry offset
Sets DRD wet scale
Sets/Displays background luminance scale
MES Command
After opening the line for operator commands (see section
Entering/Exiting the Command Mode on page 61), a data message can
be displayed using the MES command. There are eight messages
available for different uses and they numbered from 0 to 7. Refer to
section Message Types on page 63 for message type descriptions.
The command format is the following:
MES Message_number ↵
with a valid range from 0 to 7. For example, when choosing the data
message number 2, type
MES 2
↵
AMES Command
The AMES command defines the message, which the FD12P
transmits as the automatic message or as the default polled message.
Messages can also be displayed by the MES command, described in
MES Command on page 71.
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The format of the AMES command is the following:
AMES Message_number Message_interval
where
Message_number
- The valid range is 0 to 7.
- Selects the corresponding message. Any negative message
number is converted to 0.
- The message number is also the default number for the MES
command and polling.
- If only the message number is given, the previous interval
setting is used.
Message_interval
- Given in multiples of 15 seconds (= the measuring interval).
Therefore intervals 15, 30, 45 ... are valid. Other intervals are
converted to integer multiples of 15 seconds. The maximum
sending interval is 255 seconds (4 minutes 15 seconds).
- Negative or zero interval ignores the automatic sending. This
is used when messages are polled. Refer to section Message
Polling on page 69 for details.
For example, typing
AMES 1 60
↵
selects message number 1 to be sent once in a minute.
Typing
AMES 0 0
↵
selects message 0, and cancels the automatic sending.
The AMES command without parameters displays the current
selection and it is the following:
AMES
↵
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Weather Related Commands
To display or set the weather analysis parameters and results, use the
commands listed in Table 19 below.
Table 19
Command
WPAR
WSET
PRW
CLRS
WHIS
Commands for Displaying or Setting Weather
Analysis Parameters
Parameters and Results
Weather parameter message
Prw reference values
Present weather message
Clear precipitation sums
Present weather history
WPAR Command
Use the WPAR command to display the present weather analysis
parameters. Typing WPAR ↵ displays the following output:
WEATHER PARAMETERS
PRECIPITATION LIMIT
WEATHER UPDATE DELAY
HAZE LIMIT
RAIN INTENSITY SCALE
VIOLENT RAIN LIMIT
HEAVY RAIN LIMIT
LIGHT RAIN LIMIT
DRIZZLE LIMIT
HEAVY DRIZZLE LIMIT
LIGHT DRIZZLE LIMIT
WARM LIMIT
SNOW LIMIT
HEAVY SNOW LIMIT
LIGHT SNOW LIMIT
SNOW PELLETS LIMIT
SNOW GRAINS LIMIT
ICE CRYSTALS LIMIT
HAIL LIMIT
DRD SCALE
DRD DRY OFFSET
DRD WET SCALE
40
6
9000
0.80
50
8.0
2.0
15
30
3
8.0
5.0
600
1200
30
20
40
300
1.5
900.0
0.0016
WSET Command
The WSET command is used to modify the present weather analysis
parameters.
The command asks for one parameter at a time, showing the
parameter name and the current setting. Accept the current value by
pressing ENTER. You can give a new value by typing the value
before pressing ENTER.
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User's Guide _______________________________________________________________________
Type
WSET↵
and the output is as follows:
SET PRESENT WEATHER PARAMETERS
PRECIPITATION LIMIT (
40)
WEATHER UPDATE DELAY (
6)
HAZE LIMIT
( 9000)
RAIN INTENSITY SCALE ( 0.80)
VIOLENT RAIN LIMIT
(
50)
HEAVY RAIN LIMIT
(
8)
LIGHT RAIN LIMIT
(
2)
DRIZZLE LIMIT
(
15)
HEAVY DRIZZLE LIMIT (
30)
LIGHT DRIZZLE LIMIT (
3)
SNOW LIMIT
( 5.0)
HEAVY SNOW LIMIT
( 600)
LIGHT SNOW LIMIT
( 1200)
SNOW PELLETS LIMIT
(
30)
SNOW GRAINS LIMIT
(
20)
ICE CRYSTALS LIMIT
(
40)
HAIL LIMIT
( 300)
DRD SCALE
( 1.5)
WARM LIMIT
( 8.0)
The parameters are described in detail below.
Precipitation Limit
The Precipitation limit parameter is the threshold of accumulated
particle magnitudes (in FD12P internal units) that reports the
precipitation on state. The typical parameter value is 40. The smaller
value represents a more sensitive operation and faster response at the
beginning of an event.
Weather Update Delay
The Weather update delay parameter is a time as multiple of 15
seconds, during which the instant precipitation type is not changed.
The intensity may change faster.
Haze Limit
The Haze limit parameter specifies the visibility threshold for
reporting haze or mist. When the visibility is between 1000 m and the
Haze limit, the FD12P will report either haze or mist depending on the
air humidity.
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Rain Intensity Scale
The Rain intensity scale parameter is multiplied by the measured raw
intensity, which gives the reported precipitation intensity (optical).
The rain amount is scaled with the same coefficient because the
amount is a direct integral of 15-second intensities.
The typical value for the Rain intensity scale is 0.8. as the optimal
value is complex to determine; it depends on the optical, optoelectronic, and electronic parameters. No applicable factory
calibration method has been developed yet.
The precipitation measurement can be calibrated by comparing the
FD12P rain amount to measurements made with a suitable reference
rain gauge. Make the comparison after a few rainfalls with 5 mm or
more of total accumulated rain. A new scaling factor can be calculated
using the following formula:
Newscale = Oldscale × (Ref_Amount/FD12P_Amount)
where
Oldscale
=
Ref_Amount
=
FD12P_Amount =
Old value of Rain Intensity Scale
Amount measured with the reference rain gauge
Corresponding amount measured by the FD12P
Violent Rain Limit
The Violent rain limit parameter defines the minimum rain intensity
(mm/h), when the intensity is violent.
Heavy Rain Limit
The Heavy rain limit parameter defines the minimum rain intensity
(mm/h), when the intensity is heavy.
Light Rain Limit
The Light rain limit parameter specifies the maximum rain intensity
(mm/h), when the intensity is light. If the rain intensity is between the
above heavy and light limits, it is moderate.
Drizzle Limit
The Drizzle limit parameter refers to the maximum drop size (in
FD12P internal units), which can be detected as drizzle. The typical
value is 15, which has been found to be the optical signal from a 0.5
mm diameter droplet measured by typical FD12P hardware. The
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User's Guide _______________________________________________________________________
parameter value relates to the square of droplet radius. The
relationship is the following:
X = 240× R2
where
X
R
=
=
Parameter value
Droplet radius
Parameter value 30 would correspond to about a 0.7-mm droplet
diameter.
Heavy Drizzle Limit
The Heavy drizzle limit parameter refers to the minimum number of
drizzle droplets detected in 15 seconds. They must be detected before
drizzle becomes heavy (dense).
Light Drizzle Limit
The Light drizzle limit parameter defines the maximum number of
droplets detected in 15 seconds, when drizzle is light.
Snow Limit
The Snow limit parameter specifies the minimum ratio of optical
precipitation intensity to surface sensor (DRD12) precipitation
intensity, when the precipitation is snow. A half of this value is used
for separating sleet and ice pellets.
The typical value for Snow limit is 5. A smaller value directs the
FD12P to report more wet precipitation as snow.
Heavy Snow Limit
The Heavy snow limit parameter defines the minimum visibility (m)
on a two-minute average in heavy snow.
Light Snow Limit
The Light snow limit parameter defines the maximum visibility (m) on
a two-minute average in light snow. If snow is detected and the twominute visibility average is between the above heavy and light snow
limits, snow intensity is moderate.
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Snow Pellets Limit
The Snow pellets limit parameter specifies the minimum particle size
(in FD12P internal units), which is detected as snow pellets.
(Additional internal criteria are used before the precipitation type is
determined to be snow pellets.)
Snow Grains Limit
The Snow grains limit parameters refers to the maximum particle size
(in FD12P internal units), which is detected as snow grains.
Ice Crystals Limit
The Ice crystals limit parameters defines the maximum particle size
(in FD12P internal units), which is detected as ice crystals.
(Additional internal criteria are used before the precipitation type is
determined to be ice crystals.)
Hail Limit
The Hail limit parameters refers to the minimum particle size (in
FD12P internal units), which is detected as hail. (Additional internal
criteria are used before the precipitation type is determined to be hail.)
DRD Scale
The DRD scale parameter is the scaling factor for the calculated
intensity of the DRD12 surface sensor. The typical value for this
parameter is 1.5. The value is also good for a very clean DRD12.
When the DRD12 becomes dirty after some precipitation events, it
becomes more sensitive, especially for light rain. Thus, a smaller
value of the scale could be used.
Warm Limit
The Warm limit parameter defines a more flexible, maximum snow
reporting temperature limit, which is required in some areas. The
nominal value is +8 °C.
PRW Command
The Present Weather command (PRW) command, displays a verbal
format message.
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When you type
PRW↵
the system output is the following:
PRESENT WEATHER
MODERATE DRIZZLE
VISIBILITY
RAIN INTENSITY
SNOW INTENSITY
TEMPERATURE
TS
DRD SUM
7161 m
AVE 10 MIN
7533
0.16 mm/h CUMULATIVE SUM 12.16
0.0 mm/h
CUMULATIVE SUM 0
2.7
1.8
22.04
CLRS Command
The CLRS command resets (to 0.00) the cumulative sums of
precipitation. This resetting can also be done in the protocol mode by
the host computer, using the following command format:
<ESC> FD id C <CR>
Then the FD12P responds to the accepted command with the
following ASCII character:
<ACK> (06 hex)
WHIS Command
The WHIS command displays the instant precipitation type codes
(NWS) for one hour.
Type
WHIS↵
to get the results shown on the next page.
PRW HISTORY
L
RRRRRRRRR-
L
RRRRR
RRRR-
L
RRRRR
RRRR-
L
RRRRR
RRRR-
L
RRRRR
RRRR-
L
RRRRR
RRRR-
L
RRRRR
RR
RR-
L
RRRRRRR
RR-
L
RRRRRRR
RR-
L
RRRRRRR
RR-
L
RRRRRRR
RR-
L
RRRRRRR
RR-
L
RRRRRRRRR-
L
RRRRRRRRR-
L
RRRRRRRRR-
L
RRRRRRRRR-
RRRRRRRRRR-
RRRRRRRRRR-
RRRRRRRRRR-
RRRRRRRRRR-
RRRRRRRRRR-
RRRRRRRRRR-
RRRRRRRRRR-
RRRRRRRRRR-
>
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System Configuration Commands
Table 20 below lists the commands that can be used to display system
parameters and to edit current system configuration.
Table 20
Commands for Displaying System Parameters and
Editing the Current System Configuration
Command
PAR
CONF password
BAUD rate par
BLSC
Description
Parameter message
Update configuration
Set baud rate (rate 300,1200,2400,4800,9600)
Par E (7E1), N (8N1)
Set/display background luminance scale
PAR Command
The current system parameters can be displayed by using the PAR, the
System Parameters, command.
When you type
PAR
↵
the system output is shown on the next page.
SYSTEM PARAMETERS
VAISALA FD12P V 1.83 1999-11-19 SN: 46401
ID STRING:
AUTOMATIC MESSAGE
2 INTERVAL 15
ALARM LIMIT 1
0
ALARM LIMIT 2
0
OFFSET REF
130.50
CLEAN REFERENCIES
TRANSMITTER
8.9 RECEIVER
1769
CONTAMINATION WARNING LIMITS
TRANSMITTER
1.5 RECEIVER
200
CONTAMINATION ALARM LIMITS
TRANSMITTER
5.0 RECEIVER
500
SIGNAL SCALE 1
1.485 SCALE 0
0.000
TE OFFSET
58.5
TS SCALE 1
0.058 SCALE 0 -58.969
ANALOG VISIBILITY MAX 20000 MIN
10
LINEAR MODE
ANALOG OUTPUT SCALE 1
0.143 SCALE 0 713.00
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CONF Command
The configuration command, CONF, is used to set or update system
parameters and to adjust certain calibrations, reference values, and
limits. You can limit the use of this command by protecting it with a
password. New parameter values are saved in the non-volatile
memory (EEPROM).
The CONF command displays the parameters one by one and asks for
a new value. In most cases, the current value is shown as the default
value. The parameter is not updated if the user only presses the ↵ key.
You can modify the following system parameters using the CONF
command:
- Vis Alarm Limits
- Offset Freq Reference
- Temperature TE Scale
- Password Characters
- Unit Id Characters (2)
- References And Limits for Contamination Monitoring
- Analog Output Minimum Visibility
- Analog Output Maximum Visibility
- Analog Output Lin/Log
To prevent unauthorized change of the system parameters, a fourcharacter password can be set at the beginning of the CONF setting.
You can also modify the password then. When you do not want to set
or modify the password, press ↵ .
When a password has been set in the previous session, the command
format is the following:
CONF password ↵
To change the password, type
CONF password N ↵ (N stands for new).
NOTE
You must also know the previous password.
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When no password has been set, the command format is the
following:
CONF
↵
The system response to the CONF command is presented below (The
bold text refers to user actions.)
CONF. PASSWORD (4 CHARS MAX)
UPDATE CONFIGURATION PARAMETERS
UNIT ID (2 CHAR)
SET REFERENCE PARAMETERS
TE
OFFSET
OFFSET REFERENCE UPDATED
ALARM LIMIT 1
ALARM LIMIT 2
ALARM LIMIT 2
TRANSMITTER CONTAMINATION
LIMITS
WARNING LIMIT
WARNING LIMIT UPDATED
ALARM LIMIT
RECEIVER CONTAMINATION LIMITS
WARNING LIMIT
ALARM LIMIT
ALARM LIMIT UPDATED
ANALOG OUTPUT MODE
0 = LINEAR 1 = LN ( 0)
ANALOG OUTPUT RANGE
MAX VISIBILITY
MIN VISIBILITY
END OF CONFIGURATION
( 1)
( 25.9)
( 127.48) Y
(
1000)
(
200) 300
UPDATED
(
1.0) 1.5
(
5.0)
(
(
(
(
100)
500) 600
10000)
50)
The questions asked by the system are described below.
First the system asks for a new password:
CONF. PASSWORD (4 CHARACTERS
MAX)
This question is asked when there is no valid password or the existing
password is updated. If updating is requested by the N parameter and
an empty line is given for an answer, the password is removed.
Otherwise, the user gives a new password to the system.
The system asks the following:
UPDATE CONFIGURATION PARAMETERS
UNIT ID (2 CHAR)( 1)
If the FD12P unit is named by one- or two-character ID codes, the
OPEN and POLLING commands use it as a parameter. The ID code is
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also included in the data message heading. ID 1 is used as a default in
the message heading if no other ID is given. The current ID can be
removed by pressing " - " as an answer to the question.
In the multidrop configuration, where several FD12 Weather Sensors
are on the same communication line, the units are differentiated by the
ID.
The next CONF parameters are hardware- or system-dependent. They
can be changed from the factory set values for better performance or
maintenance purposes. The example configuration session is
explained in the following.
The single point calibration of the TE backup temperature
measurement can be done by giving the temperature.
SET REFERENCE PARAMETERS
TE (
25.9)
The default value is the current temperature. If it is not correct, a new
value must be typed as the answer. The new value is used to correct
the internal TE scaling factor. The TE temperature is used as a backup
in FD12P. The temperature is used in the visibility measurement to
control the precipitation effect correction algorithm. Snow and rain
have a different kind of effect on the scattering signal when it is used
for the visibility calculation.
The currently measured offset value (not a parameter) is shown in the
brackets (see next page).
OFFSET (
127.48) Y
OFFSET REFERENCE UPDATED
After receiving Y as an answer, the system accepts the offset
frequency to be the reference parameter for hardware monitoring. The
parameter value is further compared with the current value to detect
drift or other failure in the optical signal measurement electronics.
The visibility alarm limits are checked. Limit 1 is expected to be
higher than Limit 2. The limit values are expressed in meters.
ALARM LIMIT 1
ALARM LIMIT 2
ALARM LIMIT 2
(
1000)
(
200) 300
UPDATED
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In the above example, alarm Limit 2 receives a new value, 300 m.
When the visibility now weakens below Limit 2, then the data
message (0 to 2) data status is set to 2. The visibility alarm is not
shown in the status message.
The backscatter/contamination control is done by comparing the
current values of backscatter signal with the reference values given
with the CLEAN command. The limits given here are limits for the
change in backscatter signals.
TRANSMITTER CONTAMINATION LIMITS
( 1.0) 1.5
WARNING LIMIT
WARNING LIMIT
UPDATED
ALARM LIMIT
( 5.0)
The transmitter values are expressed in volt (V). The measurement
range is 0 to 13 V, where 0 V is a blocked lens. The limit value is
given as a positive value although the signal becomes smaller when
contamination increases.
A contamination change of 5 V represents about a 10 % decrease in
the transmitter's lens transmittance (as also does the same increase in
the visibility indication).
RECEIVER CONTAMINATION LIMITS
WARNING LIMIT
(
300)
(
500) 600
ALARM LIMIT
ALARM LIMIT
UPDATED
The receiver values are expressed in hertz (Hz). The measurement
range is from 0 to 10000 Hz, where 10000 Hz is a blocked lens.
A contamination change of 500 Hz represents about a 10 % decrease
in the receiver's lens transmittance.
The analog output mode and visibility range are set last. In the
logarithmic mode, the minimum visibility must be different from 0 as
LN(0) is not defined.
ANALOG OUTPUT MODE
0 = LINEAR 1 = LN ( 0)
ANALOG OUTPUT RANGE
MAX VISIBILITY
(
MIN VISIBILITY
(
END OF CONFIGURATION
10000)
50)
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BAUD Command
The baud rate and communication type can be changed by typing
following the operator command:
BAUD value communication_ type
The baud rates are 300, 1200, 2400, 4800, and 9600. The
communication types are E (7E1) and N (8N1).
The new value is saved in EEPROM and it is used also after reset or
power up. The default baud rate set at the factory is 300 baud (7E1).
Defining the communication type is optional. It does not change if the
baud rate is changed. Other baud rates than 300 baud are not allowed
with the DMX21 modem.
The BAUD command displays the current baud rate and
communication type. For an example, see the following:
BAUD RATE: 300
E71
BLSC Command
The Vaisala LM11 Background Luminance sensor can be connected
to the FD12P for ambient light measurement. Each LM11 sensor has
an individual scaling coefficient, which is defined at the factory. The
scaling coefficient is written on a label in the LM11 sensor. This
coefficient should be configured to the FD12P for correct scaling of
the measured background luminance values.
The BLSC command is used to set or display the background
luminance scale.
When you type
BLSC↵
it displays the current background luminance scale.
When you type
BLSC Scaling_factor
↵
it sets the new background luminance scale.
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If the LM11 is not connected, the scaling factor should be negative.
Value -1.0 has been set at the factory as the default value. If a positive
value is used, the sensor expects a signal from the LM11.
For an example, see the following:
>blsc
BL SCALE -1.000
>blsc 10.4
BL SCALE
10.400
If a day/night switch is connected to the serial line control input on the
FDP12 processor board, the FD12P can read the switch state and
report it as a background luminance value of 1 (day) or 0 (night). The
FD12P firmware will read the switch if the background luminance
scaling factor is set to 0.
Maintenance Commands
The maintenance commands are listed in Table 21 below.
Table 21
Maintenance Commands
Command
STA
CAL Calibrator_frequency
TCAL
CLEAN
CHEC
FREQ
DRY ON
WET ON
AN CHANNEL
Description
Displays status.
Calibration.
Temperature measurement calibration.
Sets clean references.
Displays average signal.
Displays internal signals.
Sets DRD12 dry offset.
Sets DRD wet scale.
Analog channel (0,1,3,8 ... 15 or ANALOG ID).
STA Command
The STA command displays the results from the built-in test system
as a status message. Message 3 gives the same status message as the
STA command.
When you type
STA
↵
the system output is the following:
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User's Guide _______________________________________________________________________
SIGNAL
0.39 OFFSET
126.83 DRIFT
REC. BACKSCATTER
1281 CHANGE
-1
TR. BACKSCATTER
10.3 CHANGE
0.1
TE
2.7 VBB
19.4 VH
0.6
LEDI
5.6
P15
15.1 M15
-15.0 BGND
-0.1
AMBL
0.1 DUTY
1.6
DRI21 MEASUREMENTS
TS
1.8 DRD INST
811 DRY
915.6
HARDWARE :
OK
0.14
An asterisk (*) before a value indicates an exceeded limit.
In the end, there are verbal comments on the combined errors
detected. These comments can be one or many of the following listed
in Table 22 below.
Table 22
Hardware Error Texts
Error text
BACKSCATTER HIGH
TRANSMITTER ERROR
+15 V POWER ERROR
OFFSET ERROR
SIGNAL ERROR
RECEIVER ERROR
DATA RAM ERROR
EEPROM ERROR
Description
The receiver or transmitter contamination signal
has increased more than the ALARM limit given
in the configuration.
The LEDI signal is more than 7 V or less than
-8 V.
The receiver/transmitter power is less than 14 V
or more than 16 V.
The offset frequency is zero (cable is
disconnected).
The signal frequency is less than 50 % of the
offset frequency.
Too low signal detected in the receiver
backscatter measurement.
The error is in RAM read/write check.
This is an EEPROM checksum error.
The hardware warning texts are listed in Table 23 below.
Table 23
Hardware Warning Texts
Warning text
BACKSCATTER
INCREASED
TRANSMITTER
INTENSITY LOW
RECEIVER
SATURATED
OFFSET DRIFTED
LENS HEATER OFF
DRI21 NOT
Description
The receiver or transmitter contamination signal
has increased more than the WARNING limit
selected in the configuration.
The LEDI signal is less than -3 V.
The AMBL signal is less than -9 V.
The offset has drifted more than ±5 Hz from the
reference value.
No current flowing to lens heaters.
The DRI21 board cannot be detected.
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Warning text
CONNECTED
TS SENSOR ERROR
DRD12 ERROR
LUMINANCE SENSOR
ERROR
TE SENSOR ERROR
VISIBILITY NOT
CALIBRATED
Description
The DTS14B measurement is off limits.
The DRD12 analog signal is close to zero.
The LM11 signal is zero (not checked if the BLSC
is negative).
Box temperature sensor TE measurement is off
limits.
The visibility calibration coefficient has not been
changed from the default value.
CAL Command
The CAL command is used to calibrate the visibility measurement.
The calibration is done by using opaque glass plates with known
scatter properties.
The command type is the following:
CAL Calibrator_signal_value
↵
Type, for example, the following:
CAL 985
↵
The calibrator signal value is printed on the labels of the glass plates.
Typically, the signal is close to 1000 Hz. The FD12P calculates a new
scaling factor and stores it in the non-volatile memory (EEPROM).
Refer to section Calibration on page 119 for instructions.
TCAL Command
The TCAL command is used to calibrate the sensor crossarm
temperature (TS) measurement. Only 0 °C temperature is important in
its accuracy because it is used in the identification of freezing rain.
When you type
TCAL
↵
the command displays the current scaling factors.
Without a parameter, the command displays the current scaling factors
and current TS.
When you type
TCAL TS
↵
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User's Guide _______________________________________________________________________
the command initializes the two-point calibration sequence, where two
temperatures must be simulated.
When you type
TCAL TS DTS14B_temperature
↵
a single-point calibration to the TS is made. That is, the scaling factor
TS 0 is adjusted by the command routine.
The following command
TCAL TS 0.0
↵
makes a zero calibration, if the temperature sensor DTS14B is in an
ice bath or otherwise at a temperature of 0 °C .
The following command
TCAL TS 0.0581 -59.0
↵
sets both scaling factors.
The system output is as follows:
DRI TEMPERATURE SCALES
TS 1 0.0581 TS 0 -59.0000 TS
2.8
CLEAN Command
The CLEAN command has no parameters and it is used to set the
clean references for contamination control. This command is given
during maintenance procedures after cleaning the lenses or after
replacing the transmitter or receiver board.
When you type
CLEAN
↵
the FD12P output is as follows:
CLEAN REFERENCES
TRANSMITTER
RECEIVER
UPDATED
12.0
1402
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CHEC Command
The CHEC command is used in the visibility calibration procedure to
display the two-minute average signal frequency in hertz. The
command has no parameters.
The display is terminated by pressing ESC. Pressing any other key
will pause the display. In the beginning, the eight-location buffer is
filled with the first value. The buffer is used to calculate the average
When the FDA13 calibrator is installed, the value displayed in the
message should be the same as printed on the calibrator glass plate. In
clear air the value should be near zero.
When you type
CHEC
↵
the output is the following:
SCALED FREQUENCY AVE (2 MIN)
999.9938
999.9880
>
FREQ Command
The FREQ command is for hardware monitoring. Message 4 gives the
same data line as the FREQ command.
An example of the output is the following:
>freq
SIGNAL+
OFFSET DIST SWID MAXI OWID
TE LEDI BACKS
VBB
TS
DRD
0.03
129.79 1.00
4
2
4
24.4
5.3
1303 19.5
23.1
900
0.03
129.79 1.00
4
2
4
24.4
5.3
1303 19.5
23.1
900
A new line is printed every 15 seconds. The command output is
terminated by pressing the ESC key. The first line is a title line with
the signal names.
DRY and WET Commands
The DRY and WET commands are used to check and adjust the
operation of the Rain Detector DRD12 analog signal measurement.
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The DRY command is used to set the dry signal end of the DRD12
signal normalization calculation.
When you type
DRY
↵
the output is, for example, the following:
DRD DRY OFFSET
915.6
The DRY OFFSET value must be between 850 and 980 when the
DRD12 hardware operates normally. The DRY command shows this
parameter. The parameter is set by the DRY ON command.
When you type
DRY ON
↵
the WET command without a parameter shows the scaling factor that
normalizes the DRD12 signal change from the dry state to the wet
state to 1.00. A typical value is 0.0015. An example is shown in the
following:
WET
↵
DRD WET SCALE
0.00169
The WET ON command is used to set the parameter. The DRD12
measuring surfaces must be coated with a wet cloth or immersed in
water, when the WET ON command is given. An example of the
command is given below:
WET ON
↵
AN Command
The AN command can be used continuously to display the selected
analog monitor channel. The channel ID can be used as a parameter,
instead of the channel number. Thus, the AN AMBL command is the
same as AN 12.
The message consists of the raw binary number from the A/D
converter and the corresponding scaled and filtered value.
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Type
AN AMBL
↵
WAITING FOR MULTIPLEXER
ANALOG INPUT,
118
119
AMBL
0.1
0.3
Analog Output Commands
Analog Output Calibration
The DAC output voltage is converted to current, 0 to 22 mA unscaled.
This current is then software-calibrated to give 4 mA at the minimum
visibility and 20 mA at the maximum visibility. The minimum and
maximum visibility values are set in the configuration session. A
hardware error is indicated by 0 mA.
The ACAL command sets two-bit values, 4000 and 800, to the
digital-to-analog converter. The corresponding currents measured by a
multimeter must be given as answers to the questions asked in the
commands. The analog output scaling factors, which define the
bits/mA relation, are then calculated by the software. The scaling
factors are Scale 0 and Scale 1. The FD12 calculates them as follows:
Scale 0 = 4×((4000-800)/(high current - low current))
The bit value that gives 4 mA. Scale 1 depends on the mode.
In linear mode:
Scale 1 = bits16mA / (maximum vis - minimum vis)
In logarithmic mode:
Scale 1 = (ln(max vis) - ln(min vis)) / bits16mA
bits16mA = (3200 / (high current - low current)) × 16
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When you type
ACAL
↵
the command gives, for example, the following output:
MEASURED CURRENT (mA)
22.16
MEASURED CURRENT (mA)
4.52
Data Scaling
The FD12 scales the visibility value to a binary number for the DAC
( = DACBITS) so that the minimum visibility corresponds to the
4 mA-calibrated value and maximum visibility to the 20 mAcalibrated value.
In linear mode:
DACBITS = (visibility - min visibility) × scale 1 + scale 0
In logarithmic mode:
DACBITS = (ln(visibility) - ln(min visibility)) × scale 1 + scale 0
If visibility is less than minimum visibility then
DACBITS = bits4mA = scale 0
If visibility is more than maximum visibility then
DACBITS = bits 20mA
Hardware Check
The DAC bit value from 0 to 4095 can be given as a parameter. The
value does not change until you press ESC. When the DAC command
has been given without a parameter, the analog output sweeps slowly
from 0 to maximum and from 0 until you press the ESC key.
For example:
DAC 800
↵
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Other Commands
TIME Command
The TIME command is useful for maintenance purposes.
To display the current system time, type
TIME
↵
The system output is, for example, the following:
10:11:12
To set the time, use the following command:
TIME hh mm ss ↵
where
hh =
mm =
ss
=
NOTE
Hours
Minutes
Seconds
Reset the time after a power break.
DATE Command
The DATE command is used to display the current date.
Type
DATE
↵
To set a new system date, use the command:
DATE yyyy mm dd ↵
where
yyyy =
mm =
dd =
Year
Month
Day
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RESET Command
The RESET command makes the hardware reset by the watchdog
circuitry.
The command format is the following:
RESET
↵
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CHAPTER 5
FUNCTIONAL DESCRIPTION
This chapter gives a functional description on the product.
General
The FD12P Weather Sensor is an optical sensor that measures
visibility (meteorological optical range, MOR, and precipitation
intensity and type. The FD12P measures visibility using the forward
scatter measurement principle. Light scatters from particles whose
diameter is in the order of magnitude of the light wavelength. The
amount of scatter is proportional to the attenuation of the light beam.
Larger particles behave as reflectors and refractors and their effect on
the MOR must be handled separately. Usually, these particles are
precipitation droplets. The FD12P optical arrangement allows for
individual droplets to be detected from rapid signal changes. The
FD12P software calculates the precipitation intensity by analyzing the
amplitudes of these changes. This intensity estimate is proportional to
the volume of the precipitation droplets.
The optical signal also contains some information about the
precipitation type but not enough for reliable identification. Additional
information is needed, especially in conditions where the precipitation
is very light or the weather is windy. As the extra parameter, the
FD12P measures an estimate of the water content of precipitation with
the DRD12 rain detector. In rain, the water equivalent and the volume
are equal. However, in snow the optical volume estimate is about ten
times larger. This difference of approximately one decade is used to
discern between rain and snow.
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Optical Measurement
Optical Arrangement
0110-185
Figure 21
FD12P Optical System
The following numbers refer to Figure 21 above:
1
2
3
= FDT12 transmitter
= FDR12 receiver
= Sample volume
The FD12P measures light scattered at an angle of 33°. This angle
produces stable response in various types of natural fog. Precipitation
droplets scatter light in a different manner than fog. Thus, their
contribution to visibility must be analyzed separately. The FD12P can
detect and measure precipitation droplets from the optical signal and
use this information in processing the scatter measurement results.
The FD12P has a small sample volume of about 0.1 liters (see Figure
21 above). This enables independent particles to be measured even at
quite heavy precipitation intensities. The signal levels from even the
smallest droplets can also be detected.
FDT12B Transmitter Unit
The transmitter unit consists of an infrared LED, control and
triggering circuits, LED intensity monitor, backscatter receiver, and
analog multiplexer.
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9611-002
Figure 22
FDT12B Transmitter Block Diagram
The transmitter unit electronics pulses the IR-LED at a frequency of
2.3 kHz. One PIN-photodiode monitors the transmitted light intensity.
The transmit level measurement is used to automatically keep the
LED's intensity at a preset value. The "LEDI" feedback voltage is
channeled through the analog multiplexer to the CPU for monitoring.
The feedback loop compensates for temperature and aging effects of
the light-emitting diode. On the other hand, the active compensation
slightly accelerates the LED aging. For this reason, the initial LED
current is set to a value, which guarantees several years of
maintenance-free operation.
A reset pulse (RES) from the FDR12 Receiver synchronizes the IRLED timing with the receiver's lock-in amplifier. The CPU can also
delay the transmitter firing for a special out-of-phase measurement.
This feature is used in measuring the internal noise level (offset) of the
circuitry.
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An extra photodiode measures the light scattered backwards from the
lens, other objects, or contaminants. This signal as well as several
internal signals are monitored via MUX-line.
The CPU board supplies only one voltage Vb = 10 - 13 V for both the
transmitter and receiver. This is used for heating the lenses, for the
transmitter LED heating and for producing both +5 V digital and
+15 V analog supplies. The +15 V supply is located on the FDT12B
board.
FDR12 Receiver Unit
The Receiver Unit consists of a light receiver, preamplifier, voltage to
frequency converter, backscatter measurement light source LED, and
some control and timing electronics.
9611-003
Figure 23
FDR12 Receiver Block Diagram
The receiving PIN photodiode senses the transmitted light pulses
scattered from the aerosol particles. The signal voltage is filtered and
detected by a phase-sensitive, lock-in amplifier synchronized with the
transmitter.
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The lock-in circuits take two samples of the background level and one
sample of the active signal level while the transmitter LED is lit. The
difference between the sampled voltages is amplified and then
converted into frequency.
The frequency signal is buffered by a differential line driver and sent
to the CPU board for accurate counting.
An ambient light level as high as 30 kcd/m2 does not influence the
detection of the photo diode, neither does it saturate the A4 preamplifier. The Ali signal (proportional to the ambient light) is led to
the CPU for monitoring.
An extra IR-LED is needed for backscatter or contaminant
measurement. The light level is sampled and converted into frequency
using the same method of detection described with the scattering
signal measurement.
Additional Measurements
General
The FD12P includes the DRD12 Rain Detector for estimating the
water content of precipitation and the DTS14B Temperature Sensor
for measuring the sensor crossarm temperature (TS). Both additional
sensors are measured using the DRI21 Interface Board, which is
coupled on the FD12P PICOBUS.
DRI21 Interface Board
The DRI21 is a Vaisala general-purpose sensor interface with several
analog and digital input channels. One of the DRI21 temperature input
channels (Pt100) is used to measure the crossarm temperature
(DTS14B). One 10-bit analog input channel is used to measure the
DRD12 analog signal. In addition, the DRI21 controls the DRD12
heating and reads the rain ON/OFF status.
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9807-031
Figure 24
DRI21 Block Diagram in the FD12P Application
DRD12 Rain Detector
The DRD12 analog signal is proportional to the water amount on the
sensing surfaces. Water on the DRD12 changes the capacitance of the
sensor elements. The capacitance of the elements controls the output
frequency of an oscillator. This frequency is amplified and also
converted into a voltage signal for direct analog measurement. With
dry surfaces, the DRD12 outputs about 3 V and with totally wet
surfaces 1 V. Refer to Figure 29 on page 104, section DRD12 Signal
Processing on page 104.
A droplet detector monitors the voltage signal. When a new droplet
hits the DRD12 sensing surface, the voltage changes rapidly and the
detector circuit reacts. The detector triggers a delay circuit, which
controls the precipitation ON/OFF output. When new droplets are
detected often enough, the delay circuit output will stay constantly on.
The voltage signal is measured once a second by an analog channel of
the DRI21 interface board. In addition, the precipitation (ONN/OFF
signal) is read with a digital input.
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Figure 25
DRD12 Block Diagram
The DRD12 sensing surfaces are heated by heating elements built into
the surfaces. The heating power varies automatically (by built-in
temperature control), but it can be switched off with a digital control
signal. When the heating is off, the surfaces become extremely
sensitive to all moisture in the air.
DTS14B Temperature Sensor
The DTS14B is a PT100 temperature sensor with a special mechanical
construction. The temperature is measured once a minute using the
DRI21 temperature channel.
The DTS14B is attached to the sidewall of the mast to achieve direct
thermal contact with the mast surface. The temperature (TS) is used to
select the default precipitation type and to separate freezing rain from
non-freezing rain.
FDP12 Control Unit
The FDP12 Control Unit consists of the microprocessor,
communication interface, memory, frequency measurement circuitry,
watchdog, monitoring circuitry, and digital-to-analog converter.
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9611-004
Figure 26
FDP12 Control Unit Block Diagram
The controller is based on an Intel® 8031 microprocessor. Besides
data acquisition and internal controlling, the FDP12 takes care of
communication through the RS-232 serial port. The alternative
RS-485 interface allows a simple method for multiple FD12P Weather
Sensors to communicate on the same line. The PICOBUS interface
facilitates a connection to a number of Vaisala peripheral units. The
memory includes a 512-kbit EEPROM for program code and a 256kbit static RAM for data and working parameters. For configurable
parameters, there is a serial non-volatile EEPROM.
The special frequency measurement circuitry measures the optical
signal that is converted into frequency in the Receiver Unit FDR12.
The watchdog circuit monitors the +5 V level as well as the system
operation creating a hardware reset when necessary. For internal
monitoring of analog signals, the CPU board contains an 8-bit A/D
converter. Along with Mux-signals from the crossarm, the lens
heating current and the ambient temperature are sampled. The Control
unit further includes an accurate, 12-bit D/A converter, which can be
configured for two-wire, 4 to 20 mA-current output.
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Measurement Signal Processing
Optical Signal Processing
The software running in the FDP12 CPU controls the measurement
hardware and reads the data samples. The FD12P measures in
15- second cycles as follows:
- 10 s
signal frequency and analog monitoring voltages are
measured
- 1s
receiver backscatter frequency
- 4s
offset frequency (internal noise level)
The hardware outputs an optical measurement sample every 8 ms (on
the average). The raw samples are first classified by frequency to get a
signal distribution. The distribution is then analyzed with a proprietary
algorithm, which selects a part of the distribution for signal average
calculation (Figure 27 below). The difference of the signal average
and offset average is used in the visibility calculation.
9807-033
Figure 27
Optical Raw Data (in Rain)
Precipitation causes peaks in the optical signal. These peaks are
analyzed by calculating an amplitude change distribution from the
samples. Because the signal amplitude is proportional to the droplet
size, the amplitude change distribution can be interpreted as the
droplet size distribution. The droplet size distribution is an important
parameter in determining the form of precipitation.
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9807-034
Figure 28
Optical Signal Amplitude Distribution (in Rain)
DRD12 Signal Processing
The DRD12 output voltage is measured once a second by the DRI21
interface board. With dry surfaces, the voltage is approximately 3 V
and drops when the sensing elements become wet (Figure 29 below).
0110-186
Figure 29
DRD12 Surface Signal (Heavy Rain Beginning)
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The software normalizes the measured signal and then estimates the
precipitation intensity using an empirical algorithm. The estimate is
proportional to the amount of water on the DRD12 surfaces. The
signal normalization is calibrated at the factory with dry and
completely wet surfaces.
When the heating of the sensor elements is switched off, the sensor
elements become very sensitive to ambient moisture. If the relative
humidity of the air is more than about 70 % , the surfaces produce a
measurable signal even with no precipitation. This is used as an
estimated humidity measurement in the FD12P. The estimated
humidity is used to separate between haze and mist.
As the FD12P can detect the beginning of precipitation from the
optical signal, the DRD12 heating can be turned off when there is no
precipitation. The software disconnects the heating after one hour
from the previous precipitation detection. When precipitation or
moisture is detected again, the heating is turned on for at least one
hour.
Algorithm Description
Visibility
The optical signal analysis calculates the difference of the
measurement signal and offset averages for the visibility algorithm.
The difference value (frequency) is given as a parameter to a
calibrated transfer function. The transfer function converts frequency
into visibility (MOR). A signal of one hertz corresponds to a visibility
of about 4500 m and 100 Hz about 150 m. The exact form of this
transfer function has been defined using an accurate transmissometer
(Vaisala MITRAS) as a reference.
The instantaneous (15 s) visibility values are averaged to get one- and
ten-minute average output values. The averages are calculated from
extinction coefficient values to better emulate human observations.
The extinction coefficient (σ) is defined as follows:
σ (1/km) = 3000/MOR (m)
If the signal level is less than 0.23 Hz (visibility over 15 km), the
FD12P uses extra filtering in the one-minute average MOR value. The
filter function is the following:
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MOR = (4×signal+0.1)×NEW MOR+(1-(4×Signal+0.1)×OLD MOR
where
OLD MOR =
NEW MOR =
The previous average value
A new instantanous value
The lower the signal value, the less the new instantaneous value is
included in the average. The minimum influence of the new sample is
10 %. This filtering reduces noise in the output values.
Detecting Precipitation
The precipitation onset detection is based on measuring the signal
peaks caused by precipitation droplets. The peak amplitudes that are
detected during 10 minutes are summed. When the sum exceeds a
threshold value, the sensor will indicate precipitation. The threshold
value is the Precipitation limit parameter and can be changed by the
operator.
In addition to the optical detection, the DRD12 ON/OFF signal is used
in lowest precipitation intensities. The DRD12 is also used for some
cross-checking of the optical detection.
The precipitation ending is detected when the summed optical signal
amplitudes decrease below another, lower threshold value. The
summing interval depends on the detected precipitation intensity.
Typically, the FD12P will detect precipitation ending within a few
minutes but in low intensity precipitation the detection time may reach
10 minutes.
Precipitation Intensity
The light scattering from a precipitation particle is proportional to the
volume of the particle. This proportionality is quite stable for rain
because the droplets are all quite spherical. In solid precipitation, the
shape of particles varies but is proportional to the average volume of
the particles.
The optical value of the precipitation intensity is calculated from the
distribution data of signal change and then scaled by multiplying with
the Rain intensity scale, which is an adjustable parameter. The optical
intensity value is proportional to the volume of the detected particles.
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The DRD12 data is used to calculate another estimate of the
precipitation intensity. This intensity is calculated from low pass and
high pass filtered, one-second samples. The intensity is scaled with the
DRD scale parameter. For normal operation in liquid precipitation,
the scaled DRD12 intensity estimate should be higher than the optical
intensity.
In snow, the DRD12 intensity is proportional to the water content of
the snow. Due to undercatch, however, the values are often lower than
the real water content. Also, different types of snow particles have
characteristic behaviors on the warm sensing surfaces.
The precipitation intensity in the output messages is based on both the
optical and capacitive measurements. In liquid precipitation the
optical intensity is reported as such. When frozen precipitation is
detected, the FD12P multiplies the optical intensity with a scaling
factor to get an estimate of the water equivalent intensity. This scaling
factor is calculated from the DRD12 and optical intensities. New
intensity estimates are calculated every 15 s and averaged to get the
one-minute intensity value, which is shown in the output messages.
Precipitation Accumulation
The FD12P calculates the accumulation of water (including the water
content of snow) and snow. The water sum is automatically reset
when it reaches 99 mm and the snow sum at 999 mm. There is also a
command for forced resetting by the operator or the system host
computer.
Two methods are used in calculating the water sum. In rain, the
optical intensity values are directly scaled to sum increments and
added to the accumulated sum. In other types of precipitation, an
internal scaling factor is used to get the water increment. The scaling
factor is calculated from optical and DRD12 intensities.
The snow sum is accumulated from the optical intensity when snow is
detected. The snow sum is only a coarse estimate of the thickness of
snow. In a shorter period, the accumulated snow value is a reasonable
measure of the new snow on the old snow.
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Present Weather
Precipitation Types
The ratio of the optical intensity and the DRD12 intensity estimates is
the key factor used in the precipitation type decision (see section
Precipitation Intensity on page 106). Some filtering is used in
calculating intensity ratio to get the parameter that is used in the type
finding procedure. The Weather delay parameter is also used to
eliminate unrealistically quick changes in the precipitation type. The
sensor surface temperature (TS) is used in selecting the default
precipitation type. Above Warm limit (+8 °C), the "default"
precipitation type is rain. Below -5 °C it is snow and between -5 °C
and Warm limit (+8 °C) it is unknown (P or 40).
In some areas, a more flexible snow reporting temperature limit is
required. The Warm limit, which is the upper limit for reporting snow,
is a user-definable parameter with the nominal value of +8 °C. The
parameter can be defined between +4 °C and +8 °C. Changing the
limit temperature affects the discrimination of the following
parameters:
- Snow and hail if the ratio of optical and DRD intensity is over the
Snow limit value.
- Rain&snow and Rain when the intensity ratio is between one and
Snow limit.
If this temperature limit is set higher (towards +8 °C), the FD12P
reports snow and rain&snow more often (but not above this limit
temperature).
If the temperature limit value is set lower (towards +4 °C), the default
precipitation rain is reported more often.
The precipitation code P (unknown type) is selected in cases where
the precipitation intensity (optical) is very low and the intensity ratio
appears to indicate liquid precipitation below or solid precipitation
above 0 °C.
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0201-092
Figure 30
Precipitation Type Determination Principle
The precipitation types can be divided into four main categories:
- Liquid precipitation
- Frozen precipitation
- Mixed precipitation
- Unknown precipitation
The types and their detection criteria are listed below.
Liquid Precipitation
In liquid precipitation, the optical and the DRD12 intensities are near
each other, or the DRD12 intensity is higher. Rain and drizzle are
separated by the highest peak signal (largest droplet). If liquid
precipitation is detected below 0 °C (TS), it is indicated as freezing
rain or freezing drizzle (ZR, ZL).
NOTE
The FD12P freezing precipitation detection is based on the practical
definition of "rain (or drizzle) freezing on surfaces", not on detecting
supercooled water.
a.
Rain: If the maximum droplet size is bigger than the
Drizzle limit, the precipitation type is rain. The Light rain
limit and Heavy rain limit are (approximately) the two-
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minute average intensity limits in mm/h used to set the
rain intensity type.
b.
NOTE
Drizzle: Drizzle consists only of small droplets. The
maximum droplet size allowed for drizzle is set by the
Drizzle limit parameter. The Light drizzle limit and Heavy
drizzle limit are the number of droplets in 15 s (average)
that are used to determine the drizzle intensity. The
intensity ratio (optical/DRD12) must be similar to that of
rain.
By definition, drizzle cannot be identified only by its size, but also by
its origin (stratus cloud). The FD12P reports the instant weather code
by the size information only. The 15-minute weather code in the
FD12P report is drizzle, when at least ten minutes of only drizzle
precipitation has been observed. The one-hour code is generated by
the majority principle.
Frozen Precipitation
Precipitation is frozen, if the ratio of optical intensity measurement to
DRD12 is high.
a.
Snow: For snow, the intensity ratio (optical/DRD12) must
be larger than the Snow limit parameter and crossarm
surface temperature (TS) less than +8 °C (warm limit).
b.
Snow grains: For snow grains, the droplet signal size must
be less than the Snow grains limit in size. Also the DRD12
intensity must be very small as the small snow grains
easily bounce off the sensing surfaces.
c.
Snow pellets: Snow pellets are bigger than snow grains,
but also cause very little signal on the DRD12. The Snow
pellets limit sets the minimum of the biggest particle
detected within a period of about two minutes.
d.
Ice crystals: Ice crystals are even smaller than snow
grains. The Ice crystals limit sets the maximum particle
size for ice crystals. The ice crystals are identified from
the snow grain class by size. Almost no signal is detected
from the DRD12.
e.
Hail: In principle, the intensity ratio is very high for hail
because hail is not melted by the DRD12 surfaces. In
practice, there is usually heavy rain with hail, which
makes the hail detection a little uncertain. Hail limit sets
the minimum particle size that is required for hail.
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Mixed Precipitation
The FD12P reports either rain and snow (WMO codes 67 and 68) or
ice pellets (WMO codes 74, 75, and 76) when the intensity ratio is
between one and Snow limit. The intensity is determined by estimating
the water equivalent intensity and using the rain intensity limits.
a.
Ice pellets: Ice pellets is reported if the sensor crossarm
temperature (TS) is below +3 °C and the maximum
droplet size in internal units is less than 50.
b.
Rain and snow: Rain and snow is reported when the TS is
below +8 °C (warm limit) and the criteria for ice pellets
are not met (see above).
Unknown Precipitation
Precipitation type is unknown in the following cases:
- When the default value is shown.
- When the TS is between -5 °C and +8 °C (warm limit).
- Before enough data is available for better analysis.
-
When intensity is very low.
- When the intensity ratio is not reliable.
Visibility Types
When precipitation is not detected, the weather type is determined
from visibility. The visibility types for FD12P can be divided into two
main categories:
- Fog
- Haze and mist
The visibility types and their detection are listed below.
Fog
Fog codes are reported when there is no precipitation but the visibility
is less than 1 km in an average of 10 minutes. The fog trend is
calculated from the one-hour data. The average of the latest and
earliest 20 minutes the data are calculated. The change in these
averages determines the trend. Code 20 is reported, when fog has been
reported during the preceding hour but visibility is now better than 1
km and no fog patch detection is on.
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a.
Fog patches: Fog patches (code 31) are detected from
rapid changes in visibility across the one-kilometer fog
limit. If the visibility of the one-minute average is more
than twice or less than half of the two-minute average,
then the internal patch indicator is set for about 30
minutes.
b.
Thinner fog: Fog is reported to become thinner (32) if
(latest 20-minute average - earliest 20-minute average) >
0, and the difference is greater than 30 % of the earliest
20-minute average.
c.
Stable fog: Fog has been stable (33) if the Absolute (latest
20-minute average - earliest 20-minute average) is less
than 20 % of the lower average visibility.
d.
Thicker fog: Fog is reported to become thicker (34) if
(latest 20-minute average - earliest 20-minute average) is
less than zero and the difference is more than 30 % of the
new 20-minute average.
Haze and Mist
If no precipitation is detected, a visibility code is generated. The
HAZE code (04) is used when the DRD12-estimated, relative
humidity is low and the visibility during the 10-minute average is less
than the Haze limit. If the estimated humidity is high, the MIST code
(10) is used instead of HAZE. If the estimated humidity is low and the
visibility during the 10-minute average is less than 1000 m, then code
05 (smoke, dust, or sand) is used.
When visibility increases above Haze limit × 1.2, the FD12P will
report CLEAR (code 00).
Weather Classes
The weather classes are continuous, showers, or intermittent.
The weather class is:
- Continuous, when there are less than two clear (no
precipitation) periods during the preceding hour, the
precipitation is continuous.
- Showers or intermittent, when there are more than two clear
periods during the preceding hour in the precipitation, the
weather type is intermittent.
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However, if more than 30 minutes has elapsed from the last detected
precipitation, the PRECIPITATION DURING THE PRECEDING
HOUR code is used.
Weather Code Selection
The FD12P presents the weather type using the World Meteorological
Organization (WMO) code table 4680. Some code numbers have been
adopted from code table 4677 as these codes are not included in table
4680. Precipitation type is also reported using the United States
National Weather Service (NWS) abbreviations. The complete list of
the WMO and NWS codes used in the FD12P is presented in
Appendix A on page 143. The FD12P outputs present weather data
also in the METAR present weather codes (code table 4678).
The weather type is selected every 15 seconds using the principles
described earlier. The instant weather type will be selected from the
15-second types according to the WEATHER DELAY number of
samples by majority occurrences. The instant type is reported using
both the NWS and WMO codes.
For the 15-minute and one-hour WMO weather codes, the latest one
hour of instant precipitation types is stored in a buffer. The last
15-minute and one-hour parts of this table are then analyzed. The
number of each precipitation type in the buffer is counted.
The counts are stored in a table in decreasing order by the code value
(that is, the highest SYNOP code number first). This table is then
analyzed from top down by adding the counts together until a
minimum sum is obtained. The code number associated with the last
added count is the 15-minute or one-hour WMO code. The minimum
sum is different for the 15-minute code and the one-hour code.
Applications
In the SYNOP group 7WaWaW1W2, code WaWa is for weather at the
observation time, and W1 and W2 are for weather after the last main
observation (00, 06 ... ). The FD12P codes are directly intended to be
used for WaWa. The automactic weather station will generate W1 and
W2.
The (automatic) weather station that uses the FD12P data, can in many
cases also use other weather parameters to select from the three codes
from the FD12P or even correct them. For example, the humidity
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measurement can be used to select between smoke, fog, mist, and
haze.
The 15-minute code might be a good selection for WaWa. The
one-hour values can then be used for W1 and W2 coding. Drizzle
should not be reported until all the three codes show a drizzle type.
This prevents the small droplets at the beginning and end of a shower
or in intermittent rain to be reported as drizzle.
Code table 4680 does not separate between intermittent precipitation
and showers. The FD12P data combined with the ceilometer data
would make it possible to identify showers. The extra processing
should be done in the automatic weather station software.
Internal Monitoring
Built-in Tests
Extensive, built-in tests are included in the FD12P operation. Various
voltages are measured and corresponding alarm and warning limits are
checked. Optical contamination of both the transmitter and the
receiver is continuously monitored by measuring the backscattered
light. For this purpose, an additional transmitting LED is installed in
the receiver.
The software generates alarms, if visibility is less than the given
limits. The FD12P generates warnings of suspected faulty hardware. If
a fatal hardware failure is detected, visibility data is not output (it is
substituted with /////). A status message displays the cause of the error
in status bits and the analog output is set to zero (0).
Built-in tests include a memory test, analog monitoring, and signal
measurement monitoring. The results of the monitoring measurements
are displayed in volts or hertz depending on their origin.
The program operation is monitored by the watchdog circuitry. If the
circuit is not triggered in about two seconds, it will do a hardware
reset.
Normal operation is indicated by the green LED blinking once every
second. The yellow LED is on when the FD12P measures the
visibility signal.
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During the offset measurement, the yellow LED is off. In normal
operation, the red LED is off.
Memory Tests
After resetting, the FD12P tests and clears its SRAM data memory. It
indicates an error by the red LED blinking. After 50 blinks, the FD12P
tries to start the program anyway. Usually, this causes a watchdog
reset, if the SRAM is really faulty.
The data SRAM test is also done continuously in the background in
normal operation. If an SRAM error is detected, the watchdog resets
the system
The checksum of the parameter memory (EEPROM) is calculated and
checked for test. An error in the checksum is fatal (visibility is output
as /////). The cause is displayed in the status message.
The EEPROM checksum is calculated and checked during every
updating of saved parameters.
Signal Monitoring
The FD12P measures signal, receiver backscatter, and offset as
frequencies in about eight-millisecond samples. As the measuring
times are 10 s, 1 s, and 4 s correspondingly, they must have different
numbers of samples in a batch. The FD12P checks that the frequencies
are not zero and signal sample count is bigger than the offset sample
count.
Errors in signal or offset are fatal and the data is set to /////.
The offset drift is monitored separately. The reference offset
frequency is given in the configuration session. If the drift is more
than 2.5 Hz, the software generates a warning.
Hardware Monitoring
A four-channel, analog-to-digital converter with an eight-channel
multiplexer is used to measure some signals and various voltages from
the hardware. The STA command displays the internal monitoring
values. For more details on troubleshooting, see section Values for
Internal Monitoring on page 137.
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User's Guide _______________________________________________________________________
Contamination Monitoring
The FD12P monitors both the transmitter and receiver contamination
by measuring the backscattered signal. The CLEAN command is used
to set the clean reference values of the backscatter signals. The
deviation of the backscatter signal from the clean values is
proportional to the contamination on the lenses.
The alarm and warning limits are given in the configuration session. If
the alarm limit is exceeded, data is set to ///// and an alarm is
generated. The measured values are used only for warnings and
alarms. No compensation for the visibility signal is calculated.
Transmitter backscatter is measured by an analog circuit using the
transmitter LED as a light source. Its identifier is TRB in the status
message. The TRB is smaller for higher backscatter signals. Receiver
backscatter is measured with the signal receiver using an additional,
controlled LED as a transmitter. The result is in hertz. It is bigger
when more light is scattered back (REC. BACKSCATTER).
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CHAPTER 6
MAINTENANCE
This chapter describes the overall maintenance of the product.
General
No initial calibration of the FD12P is needed because the sensor has
been calibrated at the factory. The periodic maintenance of the FD12P
Weather Sensor includes:
- Cleaning the transmitter and receiver lenses and hoods.
- Cleaning the DRD12 Rain Detector.
- Visibility calibration check and calibration if needed.
- Calibration of the DTS14B Temperature Sensor.
Before any commands can be given to the FD12P, the communication
line must be opened. Open the communication line by typing the
following:
OPEN
↵
The FD12P answer is as follows:
LINE OPENED FOR THE OPERATOR
The line can be released to automatic messages by typing the
following:
CLOSE
↵
For details, see Chapter 4 on page 59.
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User's Guide _______________________________________________________________________
Cleaning
Cleaning Lenses and Hoods
The lenses of the FD12P transmitter and receiver units must be
relatively clean to obtain reliable results. Dirty lenses give too high
visibility values. Clean the lenses every six months or more often
depending on the conditions (for example, if there are roads nearby).
Use the STA command for monitoring the system performance.
Usually, a data message is announced if there are some warnings.
Clean the lenses when the following warning appears:
BACKSCATTER INCREASED
To clean the lenses, do the following:
1.
Moisten a soft, lint-free cloth with isopropanol alcohol and wipe
the lenses. Be careful not to scratch the lens surfaces. The lenses
should dry up indicating that the lens heating is functioning.
2.
Check that the hoods and lenses are free of condensed water or
ice and snow deposits.
3.
Wipe the dust from the inner and outer surfaces of the hoods.
4.
After the optical surfaces are properly cleaned, type
CLEAN
NOTE
↵
It is not necessary to give the CLEAN command always after the
cleaning. Choose the STA command and check only that the
BACKSCATTER CHANGE value of both the receiver and the
transmitter is close enough to zero (set to zero by the previous
CLEAN command).
Cleaning DRD12 Rain Detector
The Capacitive Rain Detector DRD12 should be cleaned every six
months or more often depending on the conditions.
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To clean the rain detector, do the following:
1.
Clean the DRD12 rain detector carefully with a soft, lint-free
cloth moistened with a mild detergent. Be careful not to scratch
the surface.
2.
Check that the detector and the windshield are free of ice and
snow deposits.
Calibration
General
The FD12P has been calibrated at the factory. Normally, the FD12P
needs no recalibration as long as the circuit boards are not changed or
there is no call for warnings and alarms. The circuit boards need no
hardware calibration.
A periodic check every year is recommended. The user checks the
visibility calibration using the FDA13 calibration kit. If the check
shows less than a ± 3 % change, recalibration is not recommended as
the change is within the repeatability of the calibration procedure.
If any mechanical damage changes or weakens the optical
measurement path, that is, either the receiver or the transmitter heads
or the crossarm supporting them, recalibration is needed. If the
receiver unit (FDR12), transmitter unit (FDT12B), or the CPU unit
(FD12P) is changed, both visibility and contamination measurements
need recalibration.
Also calibrate the DTS14B Temperature Sensor once a year.
Visibility Calibration
Calibration is checked and adjusted with the FDA13 calibration kit.
The kit consists of a blocking plate and two opaque glass plates with
known scatter properties. The CHEC and CAL commands are used in
the procedure. The calibration procedure checks the zero scatter signal
and the very high scatter signal. The zero signal is obtained using a
blocking plate and the high signal using opaque glass plates.
When the visibility measurement is calibrated, visibility should be
better than 500 m. Calibration is not recommended to be carried out in
heavy rain or in bright sunshine. However, light rain is of no harm.
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User's Guide _______________________________________________________________________
When the calibrator is used in precipitation, the error will be
proportional to the area of the scatter plates, which are covered by
droplets. Make sure that this area is negligible compared with the total
area. Bright sunlight shining on the calibrator plates will increase
noise in the scatter measurement and make the CHEC command
output less stable. If calibration needs to be carried out in bright
daylight, we recommend that the crossarm be turned so that sunlight
intensity on the calibrator plates is minimized (that is, the plates are
parallel to the sunrays).
Calibration Check Procedure
Clean the lenses before the calibration. Check the cleaning procedure
in section Cleaning Lenses and Hoods on page 118. Check also the
condition of the opaque glass plates and clean them if needed.
To check the calibration, do the following:
1.
For blocking the light path, place the blocking plate near either
of the lenses, preferably near the receiver.
2.
Wait for 30 seconds.
3.
Give the CHEC ↵ command. Then wait at least two minutes.
The signal value must be between ± 0.1 Hz. If it is not, there
may be a hardware error. Check the connectors.
4.
Remove the blocking plate and terminate the CHEC command
by pressing the ESC key.
To install the calibrator, do the following:
1.
The calibrator clamp is permanently installed. If the clamp is not
installed or the old FDA12 calibrator is used, install the
calibrator clamp in the middle of the transducer crossarm. The
correct place is marked by two grooves on the crossarm. Refer
to Figure 31 on page 122. Do not tighten the clamp bolts, the
clamp needs to be adjusted later.
2.
Fasten the opaque glass plates to the tie rod. The labels with
signal values should face outwards. Take note of the signal
value printed on the plates because it is needed during the
following steps.
3.
Attach the calibrator to the clamp, tighten the rod knob. Position
the calibrator plates by lifting or lowering the tie rod. The
transmitter and receiver should point to the middle of the glass
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Chapter 6 _______________________________________________________________Maintenance
plates. In the correct position, the upper edges of the plates are
at the same level with the receiver and transmitter hood tips (see
Figure 31 on page 122). Tighten the clamp bolts.
NOTE
Take a 30-cm ruler or equivalent and place it between the hood tips.
Then lift the glass plates until they touch the ruler. Tighten the clamp
bolts. Leave the calibrator clamp in place for the next calibrations.
Extra clamps can be purchased as optional items.
4.
Move away from the optical path, and wait for 30 seconds.
5.
Give the CHEC ↵ command.
6.
After two minutes read the displayed signal.
7.
The signal value must be close to the one printed on the plates.
If the difference is less than 3 %, the calibration is correct. If
not, continue with the calibration procedure.
8.
Terminate the CHEC command by pressing the ESC key.
VAISALA _______________________________________________________________________ 121
User's Guide _______________________________________________________________________
0201-087
Figure 31
Assembling the FDA13 Calibrator
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The following numbers refer to Figure 31 on page 122:
1
2
3
4
5
6
7
8
9
10
=
=
=
=
=
=
=
=
=
=
Crossarm
Grooves
M8 x 40 DIN912, 2 pieces
Calibrator clamp
Center of crossarm
Tie rod
Pole mast
Label
Left opaque glass plate
Right opaque glass plate
Calibration Procedure
If calibration is needed according to the calibration check (see section
Calibration Check Procedure on page 120), follow the instructions
below. The opaque glass plates are installed on the crossarm as
described in the previous paragraph.
To perform calibration according to the calibration check, do the
following:
1.
Give the CAL calibrator signal value ↵ command, for
example, CAL 985.
The calibrator signal value is printed on the labels of the glass
plates. Typically the signal is close to 1000 Hz. The FD12P
calculates a new scaling factor and stores it in the non-volatile
memory (EEPROM).
2.
Type CHEC to learn the new scaling factor that should be equal to
the calibrator signal value. If the difference between the new
scaling factor and the factory calibrated one is more than 20 %,
the CAL command will be ignored. Check the FD12P and the
calibrator for hardware or mechanical errors.
If optical units FDT12B or FDR12 have been replaced, the new
scaling factor might change more than 20 % from the original
scaling factor value and thus, the CAL command is ignored. In
this case, use the FCAL command (factory calibration) during
the calibration procedure.
VAISALA _______________________________________________________________________ 123
User's Guide _______________________________________________________________________
Calibrating the DTS14B Temperature Sensor
Calibration of the DTS14 Temperature Sensor is recommended to be
carried out once a year. For the sensor accuracy, only 0 °C
temperature is important as this temperature is used to identify
freezing rain. The TCAL command is used for the calibration of the
surface temperature (TS) measurement.
For the calibration, prepare an ice bath into a thermos flask and
remove the DTS14 sensor from the mast.
Remove the holder from the mast in the following way:
1.
Open the fixing screw fully (part 3).
2.
Push the screw head to the hole with your finger.
3.
Slide the holder downwards as long as it goes.
4.
Pull the holder and sensor away from mast hole.
5.
Open the screw holding the DTS14 and pull the sensor out of
the holder.
6.
Hang a thermos flask with a S-shaped hook to the hole for
example.
7.
Put the DTS14B temperature sensor into the ice bath.
8.
To see the current scaling factors and current TS, give the
TCAL ↵ command. Then give the FREQ ↵ command.
Wait for five minutes to allow the measurement stabilize. If the
TS is 0.0°C ±0.1°C, adjustment is not necessary. Otherwise,
continue with the calibration procedure.
9.
Terminate the command by pressing the ESC key.
10.
Give the TCAL TS 0.0 command. The command makes the zero
calibration, if temperature sensor DTS14 is at 0°C temperature.
Give the FREQ command and wait again to see that the new TS
value is correct.
11.
Terminate the command by pressing the ESC key.
12.
After calibration, fix the DTS14 to the sensor holder and mount
the holder to the mast.
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0201-088
Figure 32
DTS14 Sensor Holder Assembly to Mast
The following numbers refer to Figure 32 above:
1
2
3
=
=
=
Sensor holder
DTS14
Fixing screw
VAISALA _______________________________________________________________________ 125
User's Guide _______________________________________________________________________
Removing and Replacing
This section describes in detail how to remove and replace the optical
units, the FDT12B Transmitter, FDR12 Receiver, and the Rain
Detector DRD12. You can remove the units when you suspect that
malfunction of the FD12P is caused by faults in the optical units or the
rain detector.
Removing and Replacing Optical Units
WARNING
The equipment contains dangerous voltage of 230 VAC.
CAUTION
Servicing the equipment must be performed by qualified personnel.
To remove the unit, do the following:
1.
Remove the cover at either end of the crossarm by loosening the
four screws holding the cover. Use the Allen key for removing
the screws.
2.
Remove the black, round flange that covers the optical unit by
pulling the screw in the middle of the flange. See Figure 33 on
page 127.
3.
Loosen the three-hexagon socket locking bolts with the 5-mm,
T-handle Allen key until the optical unit is loose.
4.
Disconnect the ribbon cable connector from the unit. Take note
of the position of the optical unit by looking from the lens side.
5.
Pull the receiver/transmitter unit carefully out of the hood tube.
If a thin metal piece comes out when removing the unit, set it
back to the tube end. The purpose of the metal piece is to hold
the unit in the right place.
Inspect the condition of the FDT12B and FDR12 optical units
visually. The circuit board test points of the FDT12B and FDR12 units
are described in Appendix C on page 151.
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0110-187
Figure 33
Removing the Optical Units
The following numbers are related to Figure 33 above:
1
2
3
4
5
6
7
8
9
=
=
=
=
=
=
=
=
=
Hood tube
FDT12B transmitter/FDR12 receiver
Round flange
Cover
4 screws (M6 x 16 DIN7991)
5 mm Allen key
3 locking bolts
Connector
Ribbon cable
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User's Guide _______________________________________________________________________
To replace the optical unit, do the following:
1.
Insert the FDT12B Transmitter/ FDR12 Receiver unit into the
hood. Note that the position of the unit is correct, see Figure 34
below.
2.
Connect the ribbon cable connector with the optical unit.
3.
Tighten the three-hexagon socket locking bolts with a 5-mm, Thandle Allen key.
4.
Replace the round flange firmly. Note the ribbon cable path and
make sure the cable is run along the path safely.
5.
Finally, fasten the outer cover with four screws.
6.
Perform visibility calibration.
Figure 34
Replacing the Optical Units
The following numbers refer to Figure 34 above:
1
2
3
4
5
=
=
=
=
=
FDT12B transmitter
FDR12 receiver
Photodiode
Heating elements
LED
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Removing and Replacing the DRD12 Rain Detector
To remove the DRD12, do the following:
1.
Remove the two nuts of the assembly clamp. Refer to Figure 35
below. The DRD12 Rain Detector is attached to the crossarm
with its cable only.
2.
Detach the windshield by loosening the bolt.
3.
Remove the cover of the DRD12 unit by loosening the four
screws.
4.
Loosen the hexagon nut of the cable feedthrough and detach the
wires from the screw terminal inside the DRD12 unit. Then pull
the DRD12 cable out of the unit.
5.
Deliver the entire DRD12 unit to Vaisala.
0110-189
Figure 35
Removing the DRD12 Rain Detector
VAISALA _______________________________________________________________________ 129
User's Guide _______________________________________________________________________
The following numbers refer to Figure 35 on page 129:
1
2
3
4
5
6
7
8
9
10
=
=
=
=
=
=
=
=
=
=
Wind shield
Two RainCap™ elements
Assembly clamp
White
Red
Blue
Yellow
Green
Black
Pressure compensation element
To replace the DRD12, do the following:
1.
Pull the DRD12 cable through the feedthrough of the DRD12
unit and attach the six wires to the screw terminal as shown in
Figure 35 on page 129.
2.
Tighten the hexagon nut of the feedthrough.
3.
Place the cover on the DRD12 unit and fasten the four screws.
4.
Fix the windshield with the bolt. Place the assembly clamp and
fasten the DRD12 to the crossarm by tightening the two nuts.
Calibrating FD12P Weather Sensor after Unit
Replacement
The hardware of FD12P electronics unit has been checked and tuned
at the factory. All adjustments specific to a complete sensor are made
in the software. The sensor stores the calibration factors and several
internal monitoring values in the EEPROM memory on the processor
board. The parameters in question are listed in Table 24, Table 25, and
Table 26 on page 131.
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Table 24
Parameters for Optical Measurement
Parameter
Type of Parameter
Transfer function
scaling factor
Offset reference value
Transmitter
backscatter reference
value
Receiver backscatter
reference value
Calibration constant
Command to Change
the Parameter
CAL (FCAL)
Internal monitoring
Internal monitoring
CONF
CLEAN
Internal monitoring
CLEAN
Table 25
Parameters for DRD12 Precipitation Detector
Parameter
Type of Parameter
Dry state offset value
Output scaling factor
Calibration constant
Calibration constant
Table 26
Command to Change
the Parameter
DRY
WET
Parameters for DTS14 Temperature Sensor
Parameter
Type of Parameter
Offset value
(Scaling factor
Calibration constant
Calibration constant
Command to Change
the Parameter
TCAL TS
TCAL TS)
If any electronics units are replaced, some (or all) of the parameters
may need to be updated. Table 27 below describes the necessary
operations for each unit.
Table 27
Updating Parameters
Unit
FDT12B Transmitter
Unit
FDR12 Receiver Unit
DRD12 Precipitation
Detector
DTS14 Temperature
Sensor
DRI21 Sensor
Interface
FDP12 Processor
Board
Necessary Operations
Update optical calibration,
offset reference value and
backscatter reference.
Update optical calibration,
offset reference value and
backscatter reference.
Update dry offset value
(and scaling coefficient.)
Note! Scaling coefficient
can be left unchanged
without practically any
harmful effects.
Update offset value.
Commands
CAL (FCAL)
CONF
CLEAN
CAL (FCAL)
CONF
CLEAN
DRY
(WET)
TCAL TS
Update temperature offset. TCAL TS
All of the above (including
WET).
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User's Guide _______________________________________________________________________
The parameters controlling the operation mode (automatic or polling),
message type, and weather type decision thresholds are also stored in
the EEPROM. If the processor board is replaced, these parameters
should also be checked and updated. The parameters and commands
are listed in Table 28 on page 132.
Table 28
Parameters and Commands
Parameter
Sensor ID
Message type
Sending mode
Weather parameters
Checking Command
PAR
Changing Command
CONF
PAR
WPAR
AMES
WSET
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CHAPTER 7
TROUBLESHOOTING
Warnings
WARNING
The equipment contains dangerous voltage of 230 VAC.
CAUTION
Servicing the equipment must be performed by qualified personnel.
Troubleshooting Examples
Message Indicating Warning or
Alarm
1.
Open the command mode and check the status information with
the STA command or poll Message 3 for the same information.
2.
See section STA Command on page 85 for descriptions of the
status message errors and warnings.
3.
Check the monitoring values against the internal monitoring
limits.
VAISALA _______________________________________________________________________ 133
User's Guide _______________________________________________________________________
Message Missing
1.
Check that your terminal has the correct settings. The FD12P
default is 300 bit 7E1.
If the settings are not correct, you can
- Change the baud rate, for example, to 300 baud.
- Check that you have seven data bits, even parity, one stop bit.
2.
Try the OPEN command (see section Entering/Exiting the
Command Mode on page 61) and try other commands to see if
the FD12P is already in the command mode.
3.
Go to the site with the maintenance PC (terminal), terminal
cable, tools, and the calibrator set.
4.
Check that the FD12P powered by opening the FD12P
electronics enclosure cover to check if the LEDs are blinking.
5.
If no LED is on, do the following:
- Check that the main switch is on (FDW13).
- Check the mains fuse (250 mA) and replace it if needed.
WARNING
The main fuse contains dangerous voltages of 230 VAC.
- Check the low voltage fuse on the regulator board and
replace it if needed.
- Check that all the connectors are properly inserted.
- Check the power cable and connections.
- Measure the mains voltage.
6.
If the green LED is blinking (once per second for correct
operation), do the following:
- Connect a maintenance terminal to the RS-port.
- Check steps 1 and 2.
- Try resetting by turning off power or disconnecting the fuse
on the regulator board for a few seconds.
7.
When only the red LED is lit or blinking, do the following:
- Try resetting as above.
- If the state continues, it is probably caused by either the
program memory or CPU fault.
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Visibility Value is Missing
1.
The FD12P control electronics is probably working. Check the
following:
- Check the status information with the STA command (see
section STA Command on page 85). If there are active
hardware alarms, visibility values are removed from data
message.
- Check especially P15, M15, BACKSCATTER and LEDI. See
section Values for Internal Monitoring on page 137 for the
limits.
2.
Go to the FD12P site and do the following:
- Check the cable connector at the control board.
- Check the receiver and transmitter units. Follow the
instructions in section Removing and Replacing on page 126
when removing the units.
- Check that the ribbon cable connector is properly connected.
- Pull out the circuit boards, first of the receiver (loosen the
bolts) and then the transmitter.
- Visually inspect the condition of the electronics.
Visibility Value is Continuously Too
Good
This can be caused by several reasons, some of which are listed
below. Most probably the light path from the transmitter to the
receiver is disturbed.
a.
The lenses may be excessively contaminated, which
produces a warning. Clean the lenses (see section
Cleaning on page 118).
b.
One of the hoods has been filled with snow, leaves, or
other things, for which a warning is generated. Clean the
hoods.
c.
There is condensation on the lens surfaces, which is a sign
of heating failure.
d.
An electrical fault has occurred in the transmitter or
receiver. See items in section Visibility Value is Missing
on page 135.
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User's Guide _______________________________________________________________________
Visibility is Constantly Too Low
Usually there is something disturbing in the sample volume. Check
the following:
1.
Check the condition of the hoods. If the hoods are slightly
twisted, try to align them as well as possible.
2.
Try to find a better direction for the receiver/transmitter optics.
See section Location and Orientation on page 30.
3.
There may be an electrical fault. See items in section Visibility
Value is Missing on page 135.
FDP12 Reports Precipitation When
There Is None
When temperatures are below 0 °C, only the optical measurement is
used in precipitation detection. When the temperature is above 0 °C,
the DRD12 detection is used in cross-checking the optical detection
and false detection can only be caused by problems in both
measurements.
1.
Check that there are no flashing lights close to the FD12P.
Flashing lights may cause the FD12P to detect peaks in the
optical signal.
2.
Check that there are no foreign objects in the sample volume.
Tree branches or any other moving objects in the sample volume
may cause sudden changes in the scatter signal.
3.
If a false detection has occurred in a temperature above 0 °C, the
DRD12 does not function correctly. Do the following:
- Clean the DRD12 sensing surfaces thoroughly.
- Check the DRD12 operation.
FD12P Reports Frozen
Precipitation during Rain
The ratio of optical intensity measurement to DRD12 measurement is
too high. Do the following:
1.
Check the optical calibration and DRD12 operation.
2.
Check the TS temperature sensor operation.
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3.
If everything else seems to be functioning correctly, change the
parameter settings as follows:
- If possible, check the accumulated water sum against a
reference rain gauge This will indicate how close Rain
intensity scale is to the optimal value. Decrease the scaling
factor if the FD12P rain amount is too high.
- Otherwise, increase DRD scale.
Have Jumper Settings Been
Changed?
If you have reason to believe that the original jumper settings have
been changed, see Appendix B on page 147.
Values for Internal Monitoring
The typical values are according to factory testing and are allowed to
be changed within the given minimum/maximum limits. For example,
the LEDI value is dependent on ambient temperature of more than
+25 °C and aging of the IR-LED.
The fault limits give hints for troubleshooting.
The values for internal monitoring are listed in Table 29 on page 138.
VAISALA _______________________________________________________________________ 137
User's Guide _______________________________________________________________________
Table 29
Message
Typical
DUTY
1.6 V
Indicates the pulse
ratio in lock-in
amplifier circuit.
AMBL
Ambient light.
-0 V
Min/
Max
+1 V/
+2.5 V
Values for Internal Monitoring
Fault
Description
Action
<1 V
>2.5 V
Synchronizing signal
from the receiver to the
transmitter is missing.
1.Check condition
and contact of
-flat cable
-connectors
2. Change the
receiver.
0.0 V or 5 V
The oscillator of the
transmitter is not working.
Preamplifier is not
working.
1. Change the
transmitter.
1. Change the
receiver.
-9 V/ +3 >3 V
V
<-9 V
VH
Lens heater.
0.8 V
+0.6 V/
+1.2 V
<0.2 V
OFFSET
The lowest
frequency for
measurement
signal.
REC.
BACKSCATTER
Measurement
signal from the
receiver
contamination
control circuit.
Clean value.
130 Hz
120 Hz/ <120 Hz
150 Hz >150 Hz
Rec.
backscatter
CHANGE
(Instant
backscatter clean back
scatter >
alarm limit
'BACKSCATTER
HIGH'.
Rec.
backscatter
CHANGE
(Instant
backscatter clean back
scatter >
warning limit
'BACKSCATTER
INCREASED'.
The sun is shining
directly or from reflecting
surface (water, window,
etc.) to the receiver.
No heating current is
flowing.
2. Check orientation
of FD12P.
1. Check that the
jumper X13 (CPU) is
1-2 or 2-3.
1. Check other parts
of the STA
message.
2. Change the
receiver.
Alarm that there is
Clean outside of
obstruction in the light
optical surfaces and
path. Rising value can be remove possible
caused by disturbances from
contamination of receiver the optical path.
optics - snow inside the
receiver hood - spider net
in front of the hood, etc.
Check also the
contamination limits.
Warning that there is
small obstruction in the
light path or increased
contamination on the lens
surface. Indication that
optical surface should be
cleaned in the near
future.
138 _____________________________________________________
Clean the optical
surfaces in the near
future. The
measurement values
are still reliable.
M210296en-A
Chapter 7 ____________________________________________________________ Troubleshooting
Message
Typical
TR.
BACKSCATTER
Control signal for
the transmitter
contamination.
Clean value.
LEDI
0 V ...
Actuating signal for 6.5 V
the LED control
(transmitter).
TE
Ambient
temperature.
-40°C ...
+50°C
SIGNAL
Frequency of the
transmission signal
between
transducer and
CPU (Hz) is
inversely
proportional to
visibility.
0.00 Hz
...
10000.00
Hz
Freq.
Corr.
Visibility
1 Hz
4.5 km
10 Hz
800 km
100 Hz
150 km
VBB
absolute
V BB =Vb *2 - 1.2
V
-8 V/
+7 V
16 V /
25 V
22.8 V
when Vb=12 V
Min/
Max
Fault
Description
<-15 V
>14 V
'TRANSMITTER
ERROR'
Decreasing value can be
caused as above (REC.
BACKSCATTER)
Action
>+7 V
<-8 V
Changes in the voltage
Change the
can be caused by
transmitter.
-aging of the LED
(voltage decreases)
-rising temperature
(voltage decreases)
-changes depending on
ambient temperature
(temperature control is
possibly not working).
If the voltage is between 3 V ... -8 V, the control
loop is operating properly
but the IR LED may
change for the worse in
the near future.
Sensor disconnected.
Check X14
<-60°C
connection on CPU
board.
Sensor
or
cable
is
short
>+50°C at any
circuit.
Check temperature
rate
sensor cable on
CPU board.
Connect jumper X11 1-2
on CPU board for sound.
(Speaker not normally
installed on CPU board.
Audible sound repeats
the frequency signal.
Move your hand in the
sampling volume, and
you can check the
operation of FD12P.
If no sound or no
Sound changes in range change, check other
130 ... 10000 Hz
information of the
depending on the object STA message.
movements in the sample
volume.
Power input for the
electronics is on the
<16
CPU board, connector
>25
X17, pin 4, pin 6: GND.
Vb voltage value
<21 V
is +8.6 ... +13 V.
>24 V
VAISALA _______________________________________________________________________ 139
User's Guide _______________________________________________________________________
Message
Typical
Min/
Max
+14 V/
+16 V
Fault
Description
Action
<+14.0 V
>+16.0 V
DC/DC converter is
overloaded or working
wrong.
M15
-15.0 V
Negative voltages
of the DC/DC
converter for the
transmitter/receiv
er
-16 V/
-14 V
>-14.0 V
<-16.0 V
DC/DC converter is
overloaded or working
wrong.
BGDN
~0 V
Ground potential
for the transducer,
i.e., voltage loss in
transducer cable.
-0.5 V/
+1 V
<-0.5 V
>+1 V
1. Check flat cable
between
transmitter/
receiver.
2. Change the
transmitter.
3. Change the
receiver.
1. Check flat cable
between
transmitter/
receiver.
2. Change the
transmitter.
3. Change the
receiver.
Check transducer
cable.
P15
+15.0 V
Positive voltages
of the DC / DC
converter for the
transmitter/receiver
.
Getting Help
For technical support or comments on the manual, contact the Vaisala
technical support:
E-mail
helpdesk@vaisala.com
Telephone
+358 9 8949 2789
Fax
+358 9 8949 2790
Return Instructions
If the product needs repair, please follow the instructions below to
speed up the process and avoid extra costs.
1.
Read the warranty information.
2.
Write a Problem Report with the name and contact information
of a technically competent person who can provide further
information on the problem.
140 _____________________________________________________
M210296en-A
Chapter 7 ____________________________________________________________ Troubleshooting
3.
On the Problem Report, please explain:
- What failed (what worked/did not work)?
- Where did it fail (location and environment)?
- When did it fail (date, immediately/after a while /
periodically/randomly)?
- How many failed (only one defect/other same or similar
defects/several failures in one unit)?
- What was connected to the product and to which connectors?
- Input power source type, voltage and list of other items
(lighting, heaters, motors etc.) that were connected to the
same power output.
- What was done when the failure was noticed?
4.
Include a detailed return address with your preferred shipping
method on the Problem Report.
5.
Pack the faulty product using an ESD protection bag of good
quality with proper cushioning material in a strong box of
adequate size. Please include the Problem Report in the same
box.
6.
Send the box to:
Vaisala Oyj
SWD Service
Vanha Nurmijärventie 21
FIN-01670 Vantaa
Finland
VAISALA _______________________________________________________________________ 141
User's Guide _______________________________________________________________________
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142 _____________________________________________________
M210296en-A
Appendix A _________________________________________NWS and WMO Codes Used in FD12P
APPENDIX A
NWS AND WMO CODES USED IN
FD12P
The NWS Codes
Table 30
Internal Weather Types, NWS Code
Weather Type
No precipitation
Precipitation
Drizzle
Rain
Snow
Ice pellets
Sleet
Hail
Ice crystals
Snow grains
Snow pellets
Freezing drizzle
Freezing rain
Code
C
P
L
R
S
IP
IP
A
IC
SG
SP
ZL
ZR
The NWS codes are used with intensity indicator '+' for heavy , '-' for
light, and none (space) for moderate. For example, 'R+' means heavy
rain.
Table 31
Code
00
04
05
10
WMO SYNOP Codes (4680, WaWa)
Weather type
Clear.
Haze or smoke, or dust in suspension in the air, visibility equal to or
greater than 1 km.
Haze or smoke, or dust in suspension in the air, visibility less than
1 km.
Mist.
VAISALA _______________________________________________________________________ 143
User's Guide _______________________________________________________________________
Code figures 20 to 25 are used, if precipitation or fog was observed
during the preceding hour but not at the time of observation.
Table 32
Code
20
21
22
23
24
25
WMO SYNOP Codes (4680, WaWa)
Weather type
Fog
PRECIPITATION
Drizzle (not freezing) or snow grains
Rain (not freezing)
Snow
Freezing rain or freezing drizzle
The following code figures are used if precipitation or fog is observed
at the time of observation.
Table 33
Code
30
31
32
33
34
40
41
42
50
51
52
53
54
55
56
60
61
62
63
64
65
66
67
68
70
71
72
73
74
75
76
77
78
WMO SYNOP Codes (4680, WaWa)
Weather type
FOG
Fog or ice fog, in patches.
Fog or ice fog, has become thinner during the past hour.
Fog or ice fog, not applicable change during the past hour.
Fog or ice fog, has begun or become thicker during the past hour.
PRECIPITATION
Precipitation, slight or moderate
Precipitation, heavy
DRIZZLE
Drizzle, not freezing, slight
Drizzle, not freezing, moderate
Drizzle, not freezing, heavy
Drizzle, freezing, light
Drizzle, freezing, moderate
Drizzle, freezing, heavy
RAIN
Rain, light
Rain, moderate
Rain, heavy
Rain, freezing, light
Rain, freezing, moderate
Rain, freezing, heavy
Rain, (or drizzle) and snow, light
Rain, (or drizzle) and snow, moderate or heavy
SNOW
Snow, light
Snow, moderate
Snow, heavy
Ice pellets, light
Ice pellets, moderate
ice pellets, heavy
Snow grains (from WMO 4677)
Ice crystals (from WMO 4677)
144 _____________________________________________________
M210296en-A
Appendix A _________________________________________NWS and WMO Codes Used in FD12P
Code
80
81
82
83
84
85
86
87
89
Weather type
SHOWERS OR INTERMITTENT PRECIPITATION
Rain showers, light
Rain showers, moderate
Rain showers, heavy
Rain showers, violent (>32 mm/h)
Snow showers. light
Snow showers. moderate
Snow showers. heavy
Showers of hail, with or without rain or rain and snow mixed, not
associated with thunder (from WMO 4677)
Table 34
WMO Code Table 4678. Codes Used by FD12P
Qualifier
Intensity
Descriptor
1
2
-Light
BC Patches
Moderate
(no qualifier)
Weather Phenomena
Precipitation
Obscuration
3
4
BR Mist
DZ Drizzle
SH Shower(s)
RA Rain
FG Fog
FZ Freezing
SN Snow
DU Widespread dust
SG Snow Grains
HZ Haze
+Heavy
IC Ice Crystals
PL Ice Pellets
GR Hail
VAISALA _______________________________________________________________________ 145
User's Guide _______________________________________________________________________
This page intentionally left blank.
146 _____________________________________________________
M210296en-A
Appendix B ___________________________________________ Jumper Settings and Internal Wiring
APPENDIX B
JUMPER SETTINGS AND INTERNAL
WIRING
See Figure 36 on page 148.
VAISALA _______________________________________________________________________ 147
User's Guide _______________________________________________________________________
020-090
Figure 36
Basic Electronics Enclosure Wiring
148 _____________________________________________________
M210296en-A
Appendix B ___________________________________________ Jumper Settings and Internal Wiring
CPU Board
Table 35
Jumpers
X2
X5
X7
X11
X13
Table 36
Connectors
X3
X14
X15
X16
X17
X18
X19
X20
X21
CPU Board Jumpers
Description
Memory selection 1-2 for 27256, 2-3 for 27512
Watchdog ON 1-2, reset 2-3
TM
PICOBUS powering
Not in use
Lens heating 1-2, on 2-3 with on/off driver
CPU Board Connectors
Description
PICOBUS (for DRI21 interface board)
Temperature sensor (FDE12)
To transducer crossarm (transmitter/receiver)
Not in use!
Supply voltage, pin 4: 10-12 VDC, pin 6: GND
RS-232 connector pin 1: GND, pin 2: RxD, pin 3: TxD (for
remote and maintenance use)
RS-232 control signals (for DMX21 or other options)
Analog current output (sinking type)
RS-485 (alternative use to RS-232)
DC-Regulator
Table 37
DC-regulator Connectors
Connectors Description
X1
Pin 1, 3: output for hood heaters, (pin 3: alternative status
relay output)
X2
Pin 1, 2: power input 18 ... 26 V (electronics), pin 3, 4: power
input 20 ... 24 VAC/4A for hood heaters, (pin 4: alternative
status relay input)
X3
DC output connector pin 6: GND, pin 4: +11..12 V
DRI21 Interface Board
Table 38
Jumpers
X3
DRI21 Interface Board Jumpers
Description
PICOBUS address selection
VAISALA _______________________________________________________________________ 149
User's Guide _______________________________________________________________________
Table 39
Connectors
X1
X2
X4
Table 40
Description
Ground
Supply voltage
Lens heating
Ground
Frequency non-inverting
Frequency inverting
Channel bit 2/offset mode
Analog mux. channel
Channel bit 1/backsc. led
Channel bit 0/led off
Supply voltage
Timing reset
Ambient light
Analog voltage
Analog voltage
Analog ground/spare
DRD12 supply voltage
DRD12 heater GND
Description
Rain on/off
Heater off
Analog out
Analog GND
Description
Heater AC supply (Tx)
Heater AC supply (Tx)
Heater AC supply (Rx)
Heater AC supply (Rx)
Signal name
GND
+Vb
Leh
GND
Frq5
Frq6
Cb2
Mux
Cb1
Cb0
+Vb
Res
Ali
-15 V
+15 V
AGND
+12 V
GND
Signal name
R. ON/OFF
H. OFF
A. OUT
A.GND
Signal name
HCout
HRout
HRout
HCout
DRI21 Interface Board Connectors
Description
sensor interface
auxiliary board connector
PICOBUS connector
Electronics Enclosure/Transducer Cable Signals
Enclosure
Color
FDP12
BRN
RED
ORN
YEL
GRN
BLU
VIO
GRY
WHT
BLK
BRN
RED
ORN
YEL
GRN
BLU
YEL/GRN
Enclosure
Color
X15/1
X15/2
X15/3
X15/4
X15/5
X15/6
X15/7
X15/8
X15/9
X15/10
X15/2
-
WHT/GRN
ORN/GRN
GRN/RED
ORN/RED
Enclosure
Color
X1/10
X1/13
X1/22
X1/17
L.RED
L.BLU
YEL/BLU
WHT/BLU
X1/1
X1/3
X1/3
X1/1
DRI12
FDS13
Mil
plug
A
B
C
D
E
F
G
H
J
K
B
R
A
Mil
plug
S
T
U
V
Mil
plug
L
M
N
P
Crossarm
FDT/FD
R cable
1/BRN
2/RED
3/ORN
4/YEL
5/GRN
6/BLU
7/VIO
8/GRY
9/WHT
10/BLK
11/BRN
12/RED
13/ORN
14/YEL
15/GRN
16/BLU
Crossarm
FDT/FD
R cable
Crossarm
FDT/FD
R cable
-
150 _____________________________________________________
DRD12
cable
RED
WHT
DRD12
cable
BLU
GRN
YEL
BLK
DRD12
cable
BRN
BLU
BLU
BRN
M210296en-A
Appendix C __________________________________________ Transmitter and Receiver Test Points
APPENDIX C
TRANSMITTER AND RECEIVER TEST
POINTS
There are some test points (TP) on the FD12P circuit boards for
testing. They are as follows:
Table 41
Test Point
TP1
TP4
TP5
X1/1
X1/2
X1/3
X1/4
Transmitter Test Points
Description
Reference voltage +2.5 V, ±1 %
Feedback signal
Control voltage for LED driver,
>-8 V
<+7 V
+15 V
-15 V
+5 V
GND
9611-005
Figure 37
Test Points, Transmitter
VAISALA _______________________________________________________________________ 151
User's Guide _______________________________________________________________________
Table 42
Receiver Test Points
Test Points
TP1
TP2
TP3
TP4
TP5
TP6
TP7
TP8
TP9
Description
Synchronizing pulse for factory tests
Reference voltage -2.5 V, ±1 %
+5 V
Measurement signal after high-pass filter
P15: +15 V, ±1 V
M15: -15 V, ±1 V
GND
Measurement signal after 2-stage amplifier
(AC)
Measurement signal 0 … -10 V before
V/F converter
9611-006
Figure 38
CPU
TP1
TP2
Test Points, Receiver
GND
GND
152 _____________________________________________________
M210296en-A
___________________________________________________________________________ INDEX
INDEX
A
Additional Measurements
Algorithm
AMES
Analog output commands
ACAL
Analog Output Commands
Analog Transmission
Applications
Assembling the FD12P
Automatic Message Sending
99
105
71
92
91
55
113
40
62
B
Basic Wiring
BAUD
BLSC
Built-in Tests
43
84
48, 84
114
C
Cable Selection
Cabling Principle
CAL
Calibrating the DTS14B Temperature
Sensor
Calibration
Capabilities and Limitations
Capacitive precipitation sensing
CHEC
CLEAN
Cleaning DRD12 Rain Detector
Cleaning Lenses and Hoods
CLOSE
CLRS
Communication Cable EMC-shielding
Communication Options
CONF
Connecting Cables
Connecting Internal Grounding
Connecting the Maintenance Terminal
Constructing the Foundation
35
44
87, 123
124
119
26
21, 100
89, 120
88, 118
118
118
62
78
46
50
80
43
43
55
37
Contamination Monitoring
116
crossarm17, 18, 19, 20, 22, 30, 34, 40, 42, 87,
99, 102, 110, 111, 119, 120, 123, 126, 129,
130, 149
D
DAC command
DATE
Detecting Precipitation
DRD12 Rain Detector
DRD12 Signal Processing
DRI21 Interface Board
DRY
DTS14 Temperature Sensor
92
93
106
100
104
99
89
18, 124, 131
E
Entering/Exiting the Command Mode
61
Equipment Grounding
32
Equipment Nomenclature
23
errors
31, 86, 123, 133
F
FD12P Command Set
FDP12 Control Unit
FDR12 Receiver Unit
FDT12B Transmitter
FDW13 Mains Power Supply
forward scatter measurement
FREQ
70
101
98
96
45
21, 95
89, 124
G
Grounding and Lightning Protection
32
Grounding for Testing Purposes
34
Grounding Remote Units and Communication
Cable
34
H
hardware errors
Hardware Monitoring
56
115
VAISALA _______________________________________________________________________ 153
User's Guide _______________________________________________________________________
Hardware Structure
17
Precipitation Accumulation
107
HELP
70
Precipitation Intensity
106
Precipitation Types
108
I
PRW
77
Initial Settings
56
R
Installation Procedures
37
Internal Grounding
34
Related Manuals
12
Internal Monitoring
114
Removing and Replacing
126
Removing and Replacing the DRD12 Rain
L
Detector
129
RESET
94
line voltage setting switch
45
Location and Orientation
30
S
M
Safety
12
Safety summary
13
Mains Power Supply FDW13
20
Serial Communications Settings
50
Maintenance
117
Serial Multipoint Transmission RS-485
51
Markings Used in This Manual
61
Serial Transmission RS-232
50
Measurement Signal Processing
103
Signal Monitoring
115
Memory Tests
115
Specifications
24
MES
63, 71
STA
85, 133, 135
Message 0
64
Startup Testing
56
Message 1
64
status message22, 63, 65, 83, 85, 114, 115,
Message 2
65
116, 133
Message 3
65
SYNOP
17, 22, 113, 143, 144
Message 4
66
Message 7
68
T
Message Types
63
Messages 5 and 6
66
TCAL
87, 124
MIL-connector
34, 40, 43
The FDS12 DC Voltage Regulator
20
Modem DMX21
52
TIME
93
MOR
21, 26, 30, 48, 95, 105, 106
U
Mounting to an Existing Surface
38
Mounting When Casting the Pad
38
Unloading and Unpacking
36
User Commands in Normal Operation
59
N
Using FD12P
22
NWS
113
V
O
visibility algorithm
105
ON/OFF switch
20, 45
W
OPEN
61
Operating Principle
21
warnings 13, 25, 56, 114, 116, 118, 119, 133
Optical Measurement
96
Weather Classes
112
Optical Signal Processing
103
Weather Code Selection
113
Organizing Installation
29
WET
89
WHIS
78
P
WMO codes
59, 111, 113
PAR
79
WPAR
73
Polling
69
WSET
58, 73
power cable
13, 14, 35, 43, 44, 46, 134
154 _____________________________________________________
M210296en-A