61205V

Barometric Pressure Sensor

Ma y 2007

Copyright © 2007

Campbell Scientific (Canada)Corp.

WARRANTY AND ASSISTANCE

This equipment is warranted by CAMPBELL SCIENTIFIC (CANADA) CORP. (“CSC”) to be free from defects in materials and workmanship under normal use and service for

twelve (12) months from date of shipment unless specified otherwise. ***** Batteries

are not warranted. ***** CSC's obligation under this warranty is limited to repairing or replacing (at CSC's option) defective products. The customer shall assume all costs of removing, reinstalling, and shipping defective products to CSC. CSC will return such products by surface carrier prepaid. This warranty shall not apply to any CSC products which have been subjected to modification, misuse, neglect, accidents of nature, or shipping damage. This warranty is in lieu of all other warranties, expressed or implied, including warranties of merchantability or fitness for a particular purpose. CSC is not liable for special, indirect, incidental, or consequential damages.

Products may not be returned without prior authorization. To obtain a Return

Merchandise Authorization (RMA), contact CAMPBELL SCIENTIFIC (CANADA) CORP., at (780) 454-2505. An RMA number will be issued in order to facilitate Repair Personnel in identifying an instrument upon arrival. Please write this number clearly on the outside of the shipping container. Include description of symptoms and all pertinent details.

CAMPBELL SCIENTIFIC (CANADA) CORP. does not accept collect calls.

Non-warranty products returned for repair should be accompanied by a purchase order to cover repair costs.

61205V Barometric Pressure Sensor

TABLE OF CONTENTS

1. General Description.....................................................2

1.1 Physical Dimensions.......................................................................2

1.2 Specifications..................................................................................3

2. Installation.....................................................................3

2.1 Mounting .........................................................................................3

2.2 Wiring ..............................................................................................3

Differential Wiring: ..........................................................................4

Single Ended Wiring: ......................................................................4

3. Programming ................................................................6

3.1 Program Example: ..........................................................................7

CR10X Example .............................................................................7

CR1000 Example............................................................................8

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61205V Barometric Pressure Sensor

1. General Description

The RM Young 61205V Barometric Pressure Sensor is a versatile electronic barometer with low power consumption and wide operating temperature range. It is designed to be installed in a weather-proof enclosure or indoors. Accuracy of better than r0.5 hPa (mb) is maintained over the entire pressure and temperature range. Signal output is linear 0-2500 mV. It can be operated in a power-up or continuous mode. In the power-up mode, the datalogger must switch

12 VDC to the sensor at least 3 seconds before the measurement, take a reading, then switch the sensor off to conserve power. This can be done using the switched 12V terminal on the CR10X, CR23X , CR800,

CR850, CR1000, and CR3000 datalogger. See datalogger manual

Section OV1.1.9 for a description of the power up/down programming.

2

FIGURE 1. 61205V Barometric Pressure Sensor

1.1 Physical Dimensions

Length:

Width:

Height:

14 cm (5 1/2 inches)

7.2 cm (2 13/16 inches)

2.2 cm (14/16 inch)

Dimensions include base plate.

61205V Barometric Pressure Sensor

1.2 Specifications

Operating Range

Pressure Range:

Operating Temperature:

Humidity:

600 to 1100 hPa (600 – 1100 mb)

-50 to 60

0

C

Non-condensing

Accuracy

Accuracy:

Resolution: r 0.5 hPa

Update Rate: 2

Signal Output

Analog 0-2500mV

General

Power Requirement:

Power Consumption:

7 - 30 VDC

9 mA

NOTE: The black outer jacket of the cable is Santoprene

® rubber. This compound was chosen for its resistance to temperature extremes, moisture, and UV degradation. However, this jacket will support combustion in air. It is rated as slow burning when tested according to U.L. 94 H.B. and will pass FMVSS302. Local fire codes may preclude its use inside buildings.

2. Installation

2.1 Mounting

The sensor must be protected from the elements either by being placed in a weather proof enclosure or indoors. The 61205V has four mounting holes that are spaced 1” on centre. The screws and grommets shipped with the sensor will aid in mounting the sensor inside one of Campbell Scientific’s white fibreglass enclosures. The sensor was shipped with a black rubber boot over the pressure port (upper right corner) for protection. REMOVE this boot before deploying sensor.

If the 61205V is being installed in an enclosure, use the poly tube that was shipped with the sensor to vent the pressure port to the outdoors.

Vent this tube about 1” out the cable entry port and insert one of the white hydrophobic filters (provided) into the end of the tube.

2.2 Wiring

The recommended measurement method is using a datalogger differential channel. It can be measured using a single-ended channel, but a small measurement error will be introduced due to cable lead length.

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61205V Barometric Pressure Sensor

Differential Wiring:

Colour Sensor

Terminal

CR10(X),

CR510, CR23X

White Tx-A-V Diff H

21X,

CR7

CR800, CR850

CR1000, CR3000

Diff H Diff H

Green Ref Diff L Diff L Diff L

Red Power +12V or SW 12V

∗

+12V

+12V or SW-12

Jumper from Ctrl

Port to SW 12

CTRL

∗

Black Ref G G

Clear Drain G

∗ for switching 12V power only

Single Ended Wiring:

Using single-ended measurements may be necessary in certain applications to reduce the number of analog inputs required on the datalogger. It is important to be aware of three issues concerning the

61205V Barometric Pressure Sensor and a single-ended measurement. The single-ended measurement introduces a small measurement error due to cable lead lengths. If this error is unacceptable, or if you will be powering the sensor continuously, you should use a differential measurement.

Error Caused By Lead Lengths When Using Single-

Ended Measurement

1. The signal reference (Green) and the power ground (Black) are in common inside the 61205V. When the barometric pressure is measured using a single-ended analog measurement, both the signal reference and power ground are connected to ground at the datalogger. The signal reference and power ground both serve as the return path for 12V. There will be a voltage drop along those leads because the wire itself has resistance. The 61205V draws approximately 9 mA when it is powered. The wire used in the

61205V (P/N L9720) has a nominal resistance of 17.5

Ω/1000 feet.

Since the signal reference and the power ground are both connected to ground at the datalogger, the effective resistance of those wires together is half of 17.5

Ω/1000 feet, or 8.75 Ω/1000 feet. Using Ohm’s law, the voltage drop (V d

), along the signal reference/power ground is given by the equation below:

V d

= I*R

= 9mA * 8.75 Ohm /1000 ft.

= 79 mV/1000 ft.

This voltage drop will raise the apparent barometric pressure because the difference between the signal and signal reference lead at the datalogger has increased by V d

. With an analog output

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61205V Barometric Pressure Sensor

of 0.2 hPa/ mV, the approximate error in barometric pressure is

1.58 hPa per 100 feet of cable length.

It is not recommended to compensate for this offset in your datalogger program without system testing for two reasons. First, the stated 9mA current draw is a maximum value subject to variation. Second, the stated cable resistance is a nominal value.

In order to properly compensate for lead length on a single ended measurement, the actual current draw and cable resistance must be determined.

Important Note:

2. When measuring the 61205V single-endedly, the green and black leads must both be connected to AG on the CR10(X), CR510 or to

on the CR23X, CR800, CR850, CR1000, and CR3000. Failure to do so will connect the datalogger analog and power ground planes together, which in some cases can cause offsets on low level analog measurements.

3. When using single-ended measurements on a CR10(X), CR510,

CR23X, CR800, CR850, CR1000, or CR3000 it is important to ensure that the sensor is powered down prior to making other analog measurements. Failure to turn the sensor off when the

61205V is connected as a single-ended measurement causes the power return to be connected to the analog ground on the datalogger. The return currents from the sensor could cause small offsets on other low-level analog measurements (i.e. radiation sensors).

Colour Sensor

Terminal

CR10(X),

CR510

White Tx-A-V SE

Green Ref AG

Red Power SW 12V

Jumper from Ctrl

Port to SW 12

CTRL

Black Ref AG

+12V

Clear Drain G

CR23X, 21X,

CR7

SE

CR800, CR850

CR1000, CR3000

SE

+12V or SW-12

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6

61205V Barometric Pressure Sensor

3. Programming

The 61205V draws 9mA of power when activated. Depending on your power supply it may be beneficial to conserve power. This can be achieved by powering the sensors on and off. This is done through the switched 12V port on the CR10X, CR23X,

CR800, CR850, CR1000, and CR3000

. Other loggers may require a relay (model C1701) when power consumption is a concern.

The sensor is measured using Instruction 1 SINGLE-ENDED VOLTS or Instruction 2 DIFFERENTIAL VOLTS. The reading will be in millivolts and has to be converted to barometric pressure units. 0-

2500mV = 600 to 1100 hPa (mb).

MULTIPLIER AND OFFSET CALCULATION

Output from the 61205V is 0-2500mV which corresponds to 600 to

1100 hPa (mb) of pressure. The multiplier and offset used to convert the voltage reading to hPa is: hPa = (mV x 0.2) + 600 hPa

Offset = 600

This results in true barometric pressure in hPa. 1 hPa = 1mb. The weather service and most airports correct the pressure reading at a particular station to what it would be if that station were located at sea level. This is done so that weather forecasters can obtain a clearer picture of what is happening in the atmosphere.

Use the following equation to determine the pressure correction factor.

Then add this to the offset (i.e. CorrFactor + 600 = New Adjusted

Offset). Because barometric pressure is greatly effected by elevation, the elevation of the site used in the equation should be as accurate as possible.

P = 1013.25 [ 1 – ( 1 – Elevation/44307.69231 ) ^5.253283 ]

Where Elevation is in meters above sea level.

To convert the reading to units other than hPa, use program instruction

Z=X*F(P37) and one of the values from Table 2.

TABLE 2. Multipliers to convert the hPa reading to different units

For

kPa mm of Hg in of Hg

mBar

Multiply by

0.1

0.75006

0.02953

1.0

The following program examples are not to be used verbatim. Input channels, control ports, and location labels must be adjusted for actual circumstances.

61205V Barometric Pressure Sensor

3.1 Program Example:

Turn sensor on one minute before the hour then take a reading. This allows enough time for the sensor to warm up and settle (minimum 3 seconds).

Conditions of Example:

-

Measure sensor with a differential channel

-

Signal wires are connected to Diff Chan #1

-

Control Port #1 is jumpered to SW 12V CTRL for CR10X example only

-

Red wire is connected to the SW 12V terminal

-

Desired output is kPa (Environment Canada standard)

-

TO LEAVE THE SENSOR ON CONTINUALLY, CONNECT

THE RED WIRE TO +12V AND REMOVE THE PROGRAM

INSTRUCTIONS THAT HAVE THE <><><> SYMBOLS

BESIDE THEM.

CR10X Example

; Measure 61205V Barometric Pressure Sensor one minute before the hour and

;

; output the reading.

;{CR10X}

*Table 1 Program

1: If time is (P92) ; One minute before the hour, turn on sensor.

1: 59 Minutes (Seconds --) into a

2: 60 Interval (same units as above)

3: 41 Set Port 1 High

2: If time is (P92) ; On the hour take sensor reading.

1: 0 Minutes (Seconds --) into a

2: 60 Interval (same units as above)

3: 30 Then Do:

<><><><><><>

<><><><><><>

; Measure 61205V Barometric Pressure Sensor...

3: Volt (Diff) (P2)

1: 1 Reps

2: 25 2500 mV 60 Hz Rejection Range

<<<<<<<<<<< For Single-ended Measure- ment use Volt (SE) P1.

3: 1 DIFF Channel

4: 1 Loc [ Air_PRESS ]

5: .2 Mult

6: 600 Offset ; Add necessary sea level correction to offset.

; Convert reading to kPa.

4: Z=X*F (P37)

1: 1 X Loc [ Air_PRESS ]

2: .1 F

3: 1 Z Loc [ Air_PRESS ]

5: Do (P86)

1: 51 Set Port 1 Low

<><><><><><>

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61205V Barometric Pressure Sensor

6: End (P95)

; Hourly data output…

7: If time is (P92)

1: 0 Minutes (Seconds --) into a

2: 60 Interval (same units as above)

3: 10 Set Output Flag High (Flag 0)

8: Set Active Storage Area (P80)

1: 1 Final Storage Area 1

2: 60 Array ID

9: Real Time (P77)

1: 1220 Year,Day,Hour/Minute (midnight = 2400)

10: Resolution (P78)

1: 1 High Resolution

11: Sample (P70)

1: 1 Reps

2: 1 Loc [ Air_PRESS ]

12: Resolution (P78)

1: 0 Low Resolution

Input Location Labels:

1 AIR_PRESS

SAMPLE OF PROCESSED DATA:

Array ID YEAR JULIAN DAY TIME AIR PRESSURE

60 2003 172 1300 100.34

60

60

2003 172

2003 172

1400

1500

100.39

100.42

<><><><><><>

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CR1000 Example

'Measure 61205V Barometric Pressure Sensor one minute before the hour and output

'the reading

'CR1000

'Declare Public Variables

Public Batt_Volt

Public Air_PRESShPa

Public Air_PRESSkPa

'Define Data Tables

DataTable (Table1,True,-1)

DataInterval (0,60,Min,10)

Sample (1,Air_PRESSkPa,FP2)

EndTable

'Main Program

BeginProg

61205V Barometric Pressure Sensor

Scan (5,Sec,0,0)

'Default Datalogger Battery Voltage measurement Batt_Volt:

Battery (Batt_Volt)

'Turn 61205V on one minute before the hour, using SW12V:

If TimeIntoInterval (59,60,Min) Then SW12 (1 )

'<><><><><><>

'61205V air pressure measurement in hPa. Change offset from 600 hPa to the

'appropriate sea level correction for you site:

If TimeIntoInterval (0,60,Min) Then

VoltDiff (Air_PRESShPa,1,mV2500,1,True

,0,_60H z,0 .2,60 0)

'Convert air pressure value to kPa. Other c v fa ctors are found in Table 2.

EndIf

'Call Data Tables and Store Data

Air_PRESSkPa = Air_PRESShPa*0.1

'Turn 61205V off after a reading is taken

SW12 (0)

'<><><><><><>

CallTable (Table1)

NextScan

EndProg

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