Hello,

i want to use a DT85 to query a Modbus RTU Sensor(Meier-NT Soitemperature Probe).

From my point of view i did all the necessary configuration but somehow i dont get any response from it.

Here is my Setup:

Hardware configuration:

A-Wire: TxZ
B-Wire: RTSy
Power: 12V Source
Ground: Common Ground with DGND

Software configuration:

[SERSEN_PORT]
  *BPS = 19200
   DATA_BITS = 8
   STOP_BITS = 1
  *PARITY = NONE
   FLOW = NONE
  *MODE = RS485
  *FUNCTION = MODBUS_MASTER

I guessed the flowcontroll because it is not clear from the documentation of the sensor

Reference from Sensor documentation(german):

I know that the sensor is working since when i connect it the same way to another datalogger(Meier-NT ADL-MX) it works.

Here is the output when trying to query the sensor with P56=4:

DT85> 1modbus(ad2,R3:30003)
1modbus(ad2,R3:30003)
Modbus TX >SS: 02 04753200018a3a (8)
Modbus timeout
dataTaker 85 E124 - Modbus transaction failed
1MODBUS NotYetSet

Is there any other way to debug or am i doing something wrong?

I solved it. The wiring was incorrect -.- i had to switch A and B.

Thanks for the update scholse1,

We are sorry for the late response.

The wiring of RS485 may have different meanings on labels from each manufacturer especially when they use A and B labels, but one thing remains the same when using polarity labels + and -.

Best regards,
dataTaker Expert