1771-NR/C 650 Ohm RTD Card help!!

[sparkytex]

Hello all,

I've never worked on these style of cards for the Allen Bradley PLC 5. Our digester temperatures are RTD style Temp probes through these cards. Two of them are not working reading -2000 in the data column. It appears there is no scaling done for these on the card I/O config. The raw data gets sent straight to our wonderware HMI which is then scaled 0-1600 raw to 0-160 EU. Obviously at -2000 the readout on the HMI is going to be zero. Our digester operators are cooking blind and its a big pain in the behind.

The instrument mechanic on shift says he is reading the Ohm's off the probe just fine. At this time I have 2 spare channels on the same card, but in the raw data those spares just say 8700. I would like to take the probes wires and put them on the spare channels I/O point. My question is am I on the right track. Is there a way I can fake a signal into these spare channels to see if they work? I'm not sure what voltage these cards are rated for and really how they work in general to run such a test.

I attached the PLC RSP. program and a screen shot of the I/O config. Any help at this time would be greatly appreciated!

Thanks, Tex

 

[Mickey]

The instrument mechanic on shift says he is reading the Ohm's off the probe just fine.

Ok, the probe is good but what about the wiring from the PLC to the probe?

 

[sparkytex]

I went out personally and tested everything for myself to prove out all the wiring and to read the ohms off the probes. Everything checked out fine, I then changed the wires over to the spare channels. After changing
Channels I could see the probes raw data coming into the I/O config. Just seems strange both channels failed at the same time. Thanks for the help.