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CO2 probe to CR1000

AdamPFR Dec 18, 2019 05:42 AM


I'd like to connect a Vaisala GMP222 CO2 probe to a CR1000 data logger. I'm a novice with CS loggers but keen to learn!

I dont have the user guide for the probe but think the wiring for the sensor is:

Pin   Colour   Analog signal   RS-232C

1      White                             TX

2      Brown                            TX

3      Green                             RX

4      Yellow    Signal +            -

5      Grey      Supply Gnd      Supply Gnd

6      Pink       +11-36V DC     +11-36V DC

7      Blue                                RX

8      Shield     Signal Gnd       -

I understand I can use a single ended voltage measurement (pin 4 to H, pin 5 to Gnd, pin 8 Gnd). With this wiring I get a voltage measure from this but dont know how to convert it to CO2 ppm.

Can anyone reccommend a better approach?


xiaoboxb Feb 29, 2020 05:11 AM

You need one thing called Vaisala’s GMM220 transmitter modules at first.

Then you can think about how to convert voltage to PPM of CO2 by measuring current or voltage output? Or you can connect the module to CR1000 through RS232 and directly get a digitial output.

DaveMattey Apr 2, 2020 04:01 PM

Hi Adam

I have run CR1000's with Licor CO2 analysers which have a 0-5v output. The CO2 concentration can be calculated from the output voltage

CO2ppm=(XFXZ)*V/Vmax +X

where V is the measured voltage, XF is the full scale value for CO2 output XZ is the zero value, Vmax is the full scale DAC output voltage

Maybe you can help me!  I am repurposing a CR1000 to measure CO2 with a Vaisala GM70.  However I cant fund the pin-out onfo anywhere to locate the signal pin - where did you get your info from?



JDavis Apr 2, 2020 04:16 PM

Yes, the analog should be offset of 0. The multiplier is the full scale CO2 range divided by the full scale voltage in millivolts.

For example, a unit with a 2000ppm max CO2 range and a 0-1Volt output would have a multiplier for VoltSe of  2000ppm/1000millivolts = 2.0

mark_StFXU Jun 24, 2021 06:32 PM

Wondering if anyone has thoughts here for a similar setup....

Vaisala 343GMP Co2 probe

Allows 0-5V analog output range, 5V (voltage high)= 0.00-100,000.00 ppm (adjustable), beyond 10-20,000ppm, analog signal becomes very distorted.

Using a very basic singled ended command with ->

multiplier = high voltage ppm (100,000) / voltage range (5000mV) = 20 ppm/mV = multiplier (20)

Trying to setup serial coms, works great with the PC/terminal, but unable to get the logger to communicate through ComPort.

Very inexperienced with serial programming, but fairly confident with analogue measurements - attaching the script


'CR1000 Series Datalogger

'Date: June 24/2021
'Program author: Mark

'Declare Constants

'Declare Public Variables
Public PTemp, Batt_volt
Public co2string As String * 30, SplitStrings(3) As String * 16
Public FloatValue As Long
Public IntegerValue As Long
Public NBytesReturned

'Declare Private Variables
'Dim Counter

'Define Data Tables.
DataTable (Test,1,1000) 'Set table size to # of records, or -1 to autoallocate.
	DataInterval (0,15,Sec,10)
	Minimum (1,Batt_volt,FP2,False,False)
	Sample (1,PTemp,FP2)
	Sample (1, IntegerValue, FP2)

'Define Subroutines
	'EnterSub instructions here

'Main Program
  SerialOpen(Com1, 19200, 0, 0, 500)
	Scan (1,Sec,0,0)
		PanelTemp (PTemp,60)
		Battery (Batt_volt)
		SplitStr (SplitStrings(),co2string,",",3,5)    
		'Enter other measurement instructions
		'Call Output Tables
		CallTable Test


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