Communication Issue Humidity and Temperature Transmitter

Hello all,

I am having an issue with the relative humidity and temperature transmitter (specifically HUM C - Temco Temp and RH Transmitter). I am using an RS485 to USB converter to connect this unit to a data logger (Congrego - Congrego Data Logger).

I am able to poll both of these values and the settings are correct for receiving the data, however less than 50% of the polls are receiving a value from the transmitter:

Modbus Polling Settings:

  • Baud Rate: 115200
  • Data Bits: 8
  • Parity: None
  • Stop Bits: 1
  • Handshake: None

Temperature Polling:

  • Register Polled: Holding Register
  • Register Address: 101

Relative Humidity Polling:

  • Register Polled: Holding Register
  • Register Address: 304

Any ideas what might be causing this issue? Potentially I am missing something very simple.

Either way, thank you for your help and your time,
. James

I believe there is a setting in the T3000 front end for adding a short delay on the modbus replies. The hum can reply too quickly and some polling devices need a little delay before the reply. check around in the t3000 software and it should show up. also you could try polling with a PC which can switch from poll (sending) to receive very fast, see if the issue persists.


In T3000, select your device, then select Configuration and Advanced Parameters (gear icon), you will see a setting for Modbus Reply Delay; I believe the default setting is 5 mSec.

Regards, Steve

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