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modbus sensor connection CR1000x

cc_user May 31, 2019 07:25 AM


We would like to connect a CO2 Engine® ELG sensor to a CR1000x logger but we are having some troubles so far.

The modbus specifications for this sensor can be found under the following link:

We are programming the logger in CRBasic, you can find the program below:

Public PTemp, Batt_volt
Public GHGconc As Long 
Public Result As Float

'Declare Private Variables
'Dim Counter

'Define Data Tables.
DataTable (Your_Table,1,-1) 'Set table size to # of records, or -1 to autoallocate.
	DataInterval (0,10,Sec,10)
	Minimum (1,Batt_volt,FP2,False,False)
	Sample (1,PTemp,FP2)
	Sample (1,Result,FP2)
	Average (1,GHGconc,FP2,False)

'Define Subroutines
	'EnterSub instructions here

'Main Program
  SerialOpen (ComC7,9600,19,0,50,2)  
	Scan (5,Sec,0,0)
	  ModbusMaster (Result,ComC7,9600,254,4,GHGconc,4,1,2,50,1) 
		PanelTemp (PTemp,60)
		Battery (Batt_volt)
		'Enter other measurement instructions
		'Call Output Tables
		CallTable Your_Table

I don't get any error (Result =0), but i don't get a functional connection either. When i check the comport using device config utility (--> terminal), i get following output: 


21:09:50.036 T FE 04 00 03 00 01 D5 C5 ........
21:09:50.048 R FE 04 00 03 00 01 D5 C5 ........

The received signal is just an echo of the transmitted signal.

Moreover, the slave address does not affect the result.. And when i unplug (cut power, only UART connection) the sensor it still produces a response, but fairly random (no exact echo). 

The sensor works fine when we connect it to the computer using a TTL-232R-3V3-cable (data can be visualised using a piece of software). So the sensor and modbus module work.

Any suggestions?


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