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Analogue Input Faults


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I have a 7" UniSTream with a WCB-1 adapter.

I am using this PLC for a very simple task of monitoring contents in a tank and then controling some relay outputs depending on the tank contents level.


I have a pressure transmitter connected to a analogue input 0 and this was working correctly whilst setting up - I was seeing the correct output from the transmitter on the PLC. I also had a type K thermocouple connected to RT2 input - again during setup this was giving me a correct reading at ambient (approx 20 Celsius).

Now, during some updating of the logic, my transducer input is showing over range constantly (16689 units when the adapter is scaled to give 16383 maximum output) and my thermocouple is showing a tempoerature reading of +4359 Celsius.

I have checked the various status' of the WCB-1 and this is the outcome:

IO - Status 00000000

Analogue Input Status Input 1  (transmitter connected) - 2

Analogue Input Status Input 1  (transmitter disconnected) - 16

Internal Info - 363


I have uploaded a blank project to the PLC, and I am still getting the same problem. Does anyone have any idea why I have run into this problem?


Thanks in advance


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  • 3 weeks later...
  • MVP 2023

Take a step back and verify your electronics.  You may have a ground potential difference, especially if the transducer and the PLC have different power sources.

Disconnect the thermocouple.  Hook up your transducer in series with a DMM  and measure the current.  Hook the thermocouple back up and see if it changes.

Joe T.


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