M102729 SONIC Anemometer, Heated

M102729 SONIC Anemometer, Heated
SENSORS
MANUAL – HEATED SONIC ANEMOMETER, S2
P/N M102729 Rev -
1.0 INTRODUCTION
2.0 INSTALLATION
Climatronics’ heated sonic anemometer is designed
as a stand-alone sensor to provide accurate
measurements of wind speed and wind direction. An
internal fluxgate compass is available as an option.
The unit has no moving parts and is ideally suited for
use wherever reliable, maintenance free operation
over a wide operating range under adverse operating
conditions is required. The anemometer is equipped
with thermostatically controlled heaters for ice-free
operation.
Be sure to mount the sensor in a clear, open area to
minimize any turbulent effects caused by local
obstructions (e.g., trees, buildings, etc.). The sensor
is typically installed on Climatronics P/N 102286
pre-wired sensor mount.
The keyway in the
connector on the base of the sensor is matched to the
keyway on the mount.
Please see the configuration table on the last page
of this manual. Compare it to the serial label on
your sensor for your exact configuration.
1.1 SPECIFICATIONS
Attach the sensor to the 102286 mount by inserting
the sensor into the mating connector on the mount
and screwing the collar onto the sensor connector.
If your sensor is not equipped with a fluxgate
compass you will need to align the posts with the
black marks towards either True North or Magnetic
North depending on your application.
PERFORMANCE:
WS Range:
0-145 mph (0-65 m/s)
Accuracy:
WS 1.1 mph (0.5 m/s) or
± 5%
WD ± 5° @ wind speeds
> 5 mph (2.2 m/s)
Resolution:
.22 mph (0.1 m/s)
Loosen the set screws in the end of the Nu-Rail
fitting that secures the pipe that the sensor is mounted
on, rotate the sensor to North, then retighten the set
screws.
ELECTRICAL:
Measurement Format: Two orthogonal axis
North-South and East-West
Measurement Rate: Approx. 2 Hz each axis
Operating Frequency: 40 kHz
Signal Output: RS232C or RS485 @19.2 K baud
(see section 5.0)
Power Requirements: 6 - 15 Vdc: 100 mA
[email protected] 12 Vdc (sensor)
24 Vac, 6A (heaters)
Please refer to Figures 1 and 2 for reference.
PHYSICAL:
Size:
Weight:
Mounting:
The connector keyways assure correct alignment if
the sensor is removed and re-installed at any time.
N
9.25 inches (20.3 cm) x
4 inches (10.15 cm) dia.
3.0 lb. (1.4 kg.)
MS3106F18-1S Connector
CLIMATRONICS CORPORATION
Figure 1
(631) 567-7300
5.0 USER INTERFACE
The output of the Sonic is a serial data stream.
Typically the output is set for 19.2k baud (N/8/1) and
outputs the data string approximately once per
second. The data is easily viewed and can be
displayed and captured using Climatronics
WeatherView Software or Windows HyperTerminal
that is supplied on most Windows operating systems.
To find HyperTerminal click Start, Programs,
Accessories, Communications, HyperTerminal. An
example of the output format is shown below:
N
01+H0012 02+006.8 03+063.2 CR/LF
The first parameter is the serial number of the sensor
(H0012), the second parameter is the wind speed and
the third parameter is the wind direction. All
parameters have fixed decimal points with leading
zeroes.
Figure 2
3.0 INPUT/OUTPUT CONNECTIONS
The sensors’ pin designations are as follows:
PIN
A
B
C
D
E
F
G
H
I
J
FUNCTION
Ground
7 - 36 Vdc
Not Used
WS analog (option)
WD analog (option)
Heater Control
RS232 Receive Data or RS485B (+)
RS232 Trans. Data or RS485A (-)
Heater 24 V
Heater 24 V
4.0 USER DEFINED OPTIONS
Fluxgate Compass
An internal fluxgate compass is available with the
Sonic Weather Station.
Note: The wind direction output will be relative to
magnetic north if the fluxgate compass is selected.
Note: The optional wind tracker output is a special
hex data string that cannot be viewed as shown in
the above example.
Please refer to your specific sensor configuration
for output ranges.
6.0 THEORY OF OPERATION
6.1 Winds
Climatronics’ sonic anemometer operates on the
principal that the speed of the wind effects the time it
takes for sound to travel from one point to a second
point. If the sound is traveling in the direction of the
wind then the transit time is decreased. If the sound
is traveling in a direction opposite the wind then the
transit time is increased. This principal is well
known and is the basis of most sonic anemometers.
In mathematical terms:
t1 = d / ( c + u)
t 2 = d / ( c − u)
where t1= transit time from 1 to 2
t2= transit time from 2 to 1
d= distance between 1 and 2
c= speed of sound
u= wind speed
CLIMATRONICS CORPORATION
(631) 567-7300
If the equations are solved for c+u and c-u and the
difference taken:
c+u-(c-u)=d/t1-d/t2
u=d/2*(1/t1-1/t2)
There are many ways to implement a sonic
anemometer based on this equation and in fact most,
if not all sonic anemometers operate according to this
principal. It is important to note that the equation for
wind speed is independent of the speed of sound.
This is important because the speed of sound is not a
constant but is very dependent upon air temperature,
changing from 360 m/s at +50 °C to 300 m/s at -50
°C. Note that this change of 60 m/s is as great as the
range of most sonic anemometers. The speed of
sound is also affected by humidity and pressure,
however their effect is small compared to the effect
of temperature. It is interesting to note in passing
that the equations can also be solved for the speed of
sound and the air temperature can be determined
from the speed of sound.
The relationship between the speed of sound in air
and the air temperature can be described by the
following equation:
c = 20. 06 T + 273
T=temp °C
The equation for u above does not account for any
delays in the electronics nor for any effect
temperature might have on these delays. Because of
this the path length d is generally made on the order
of 10 cm or more. The longer the path length the less
significant the other time delays. These design
considerations and others lead to the sonic
anemometers with which we are all familiar.
Transducers are supported on long thin arms in an
array to measure the components of the wind. The
supports and the transducers are as slender as
possible to minimize their effects on the wind field.
These traditional sonic anemometers can be designed
to measure one, two or three components of the wind.
Sonic anemometers of this type are generally
accurate, exhibit high resolution, output temperature
as well as wind speed and direction and are very
responsive. They also are usually delicate, require
extensive software to correct for transducer
shadowing, and are expensive. Sonic anemometers
of this type are generally used for research.
Climatronics’ goal in developing a sonic anemometer
was to design a unit that could replace cup and vane
and propeller anemometers in terms of cost and
accuracy and at the same time be more rugged. We
also wanted an anemometer that could be kept icefree at reasonable power levels and without
expensive components to transmit heat to the rotating
parts such as the cups. Size was determined in part
because it was desirable that it have the same overall
dimensions as Climatronics’ TACMET sensor for
purposes of interchangeability. All of these
considerations dictate that the transducers will be
close together resulting in a short path length. The
short path length requires that all system delays be
accounted for.
If the equations for the transit time above are
rewritten to include the delays in the system then we
have:
t1 = d / ( c + u) +t1’
t 2 = d / ( c − u ) +t2’
t1’= delays due to transducers and electronics
t2’= delays due to transducers and electronics
t1-t2 = d/(c+u)+t1’-d/(c-u)-t2’
if t1’= t2’
t1-t2 = d/(c+u)-d/(c-u)
rearranging terms
u = -(t1-t2)*(c2-u2)/2d
At first this expression looks difficult to evaluate. It
is required to measure the temperature to assign a
value to c and the expression c2-u2 contains the
variable we are trying to solve for. The advantage is
that it is possible to measure (t1-t2) with greater
accuracy then it is to measure either t1 or t2. The
correction required due to the variation of the speed
of sound with temperature is also readily
accomplished. Note that the term (c2-u2) varies by ±
20% over the range of 0 to 50 m/s and -50 to +50 °C.
Note also that if c is corrected for temperature and u
is set equal to zero then the term c2-u2 is in error by
less then 3% from 0 to 50 m/s.
CLIMATRONICS CORPORATION
(631) 567-7300
Where the greatest accuracy is required the
equation can be solved for u and then this value
of u can be substituted back into the equation to
solve for a more accurate value of u. The design
that has evolved consists of two tapered
cylinders separated from each other by
approximately 10 cm. All of the transducers are
mounted in the upper cylinder pointing down.
Sound is transmitted toward the lower cylinder
and reflected back towards the upper cylinder as
shown:
D
X1
θ
u cos θ
X2
u
S L/2
L/2
θ
u cos θ
u
Wind tunnel tests have shown that the airflow
between the upper and lower housing is not
greatly affected by the housings themselves
through tilt angles in excess of ± 20 degrees. In
this sense the sensor has an almost cosine
response similar to a propeller anemometers.
6.2 Fluxgate Compass
The P/N 102294 internal compass is low power
and compact, and is a complete compass or
magnetic sensor module that integrates easily
into the Sonic. The internal compass uses two
magneto-inductive sensors, which change
inductance with different applied magnetic field
strengths, to sense magnetic fields.
The Sonic microprocessor measures the output
of the internal compass and then corrects the
wind direction data for the orientation of the
sensor. The output of the Sonic wind direction
is relative to magnetic North when a compass
has been specified.
7.0 CALIBRATION
Figure 3
The transmission time is affected only by the
horizontal component of the wind. Transducers
are used as both transmitters and receivers. In
this way the close match required for t1’ = t2’ is
achieved. Temperature is also measured but is
not corrected for solar radiation errors. This
temperature measurement is suitable for speed of
sound corrections but not for most
meteorological purposes. When more accurate
temperature information is required a multi-plate
shield is added to the unit.
The sensor requires a wind tunnel for calibration.
Climatronics can provide NIST traceable
calibration in our wind tunnel. A portable Zero
Wind Test Fixture, P/N 501506 is available for
purchase. Please contact the factory for further
details.
8.0 MAINTENANCE
Because the sensor has no moving parts to wear
out, periodic maintenance is not required. In
extremely corrosive environments, the condition
of the connector used to mount the sensor should
be checked. There are no adjustments or user
repairable parts located inside the sensor.
CLIMATRONICS CORPORATION
(631) 567-7300
Terminal Commands
RS232/RS485 Terminal Mode Commands
Terminal mode is activated by entering three carriage return characters within a 2 second period.
Terminal mode times-out after 2 minutes of inactivity.
Successful entry into Terminal Mode will return the prompt:
Command (HE for Help, QU to Quit):
HE - Display Help Menu
HE
Display the Help menu
Command: HE<cr>
HE - This Help Menu
BV - Battery Voltage Printout Toggle On/Off
CV - Compass Heading Printout Toggle On/Off
MD - Set Magnetic Declination
OI - Set Output Interval
QU - Quit command mode and save any changes
SA - SDI Address
SB - Set Baud rate
SP - Sign-on Prompt Toggle On/Off
ST - Set Serial Trigger Address
SU - Set Speed Units
TU - Set Temperature Units
VN - Display Firmware Version Number
SU - Wind Speed Units
Read or Set the serial port’s output Units for Wind Speed
COMMAND
SU<cr>
SU0<cr>
SU1<cr>
SU2<cr>
SU3<cr>
RESULT
Report Units setting
M/S
MPH
Knots
KPH
TU - Temperature Units
Read or Set the serial port’s output Units for Temperature
COMMAND
TU<cr>
TU0<cr>
TU1<cr>
RESULT
Report Units setting
Fahrenheit
Celsius
CLIMATRONICS CORPORATION
(631) 567-7300
SB - Serial Baud Rate
Read or Set the serial port’s Baud Rate
Note: This command is not supported by SDI-12 or Tracker Output.
SDI-12 is fixed at 1200 baud.
CAMEO/ALOHA and Tracker output are fixed at 9600bBaud.
COMMAND
SB<cr>
SB1<cr>
SB2<cr>
SB3<cr>
SB4<cr>
SB5<cr>
RESULT
Report Baud Rate setting
1200 baud
2400 baud
4800 baud
9600 baud
19200 baud
Note: Baud rate changes take effect after cycling power to the sensor.
BV - Toggle Battery Voltage Printout in data string
Read or Set the Battery Voltage output option for the serial port
COMMAND
BV<cr>
BV0<cr>
BV1<cr>
RESULT
Report option setting
Battery Voltage printout Disabled (Default)
Battery Voltage printout Enabled
CV - Toggle Compass Heading Printout in data string
Read or Set the Compass Heading output option for the serial port
COMMAND
CV<cr>
CV0<cr>
CV1<cr>
RESULT
Report option setting
Compass Heading printout Disabled (Default)
Compass Heading printout Enabled
MD - Magnetic Declination
Read or Set the Magnetic Declination
COMMAND
MD<cr>
MDXX.X<cr>
RESULT
Report Magnetic Declination setting
Set Declination to XX.X Degrees
Note: West declination values are entered and reported as negative values.
ST - Serial Trigger
Read or Set the Serial Trigger character string (Poll command)
COMMAND
ST<cr>
ST XXXXXX<cr>
RESULT
Report Serial Trigger string setting
Set Serial Trigger
VN - Software Version Number
Report the current Software Version Number
COMMAND
VN<cr>
RESULT
Report current Software Version
CLIMATRONICS CORPORATION
(631) 567-7300
OI - Output Interval
Read or Set the Output Interval for the serial port
Note: This command is not supported by SDI-12, CAMEO/ALOHA, or Tracker Output.
COMMAND
OI<cr>
OI1<cr>
OI2<cr>
OI3<cr>
OI4<cr>
OI5<cr>
OI6<cr>
RESULT
Report Output Interval setting
Sensor Output every 1 second (Default)
Sensor Output every 2 seconds
Sensor Output every 5 seconds
Sensor Output every 15 seconds
Sensor Output every 30 seconds
Sensor Output every 60 seconds
SP - Sign-On Prompt
Read or Set the Sign-On Prompt output option at power-up for the serial port
COMMAND
SP<cr>
SP0<cr>
SP1<cr>
RESULT
Report option setting
Sign-On Prompt Disabled (Default)
Sign-On Prompt Enabled
QU - Quit
Exit the command mode and query to save any changes.
Command (HE for Help, QU to Quit): QU<cr>
To save changes type 'Y' : N<cr>
No changes were made
Restarting
CLIMATRONICS CORPORATION
(631) 567-7300
102729 SONIC Options Configuration Guide
Base Part Number
Serial Output
Options
102729RS232 A
RS485 B
Baud / Output
Options
1200
2400
4800
9600
19200
485 Tracker
NMEA
Analog Options
None
0 - 1 Volt
0 - 5 Volt
0 - 2.5 Volt
1 - 5 Volt
Averaging Options
Instantaneous
Running Avg
Reserved
Reserved
Speed Units
MPH
M/S
Knots
Kilometers/Hr
MPH
M/S
Knots
MPH
Compass Option
1
2
3
4
5
6
7
C0
C1
C2
C3
C4
F
G
H
J
0 to 145
0 to 65
0 to 125
0 to 234
0 to 100
0 to 50
0 to 100
0 to 25
1
2
3
4
5
6
7
8
None
K
11709 Micromag2
L
Table 1
Climatronics Corporation
140 Wilbur Place Bohemia, NY 11716 (631) 567-7300
www.climatronics.com
Revision
-
Description
Released to Production
Date
03/26/07
Approved
D.A.
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