Honeywell 20KNTC to AB plc?

[kbnikki]

We are currently considering switching our HVAC control from Honeywell to AB. I was tasked with tracking down all of the devices to determine compatibility. I'm wondering if anyone has experience trying to connect Honeywell sensors to an AB plc?

Almost all of the current AIs are 20kohm ntc thermistors with resistance ranging from 839kohm-695ohm. From what I've been able to find, the 1756IR6I is the only module that uses ohms, and it doesn't look to go above about 4kohm.

Swapping out the currently Honeywell sensors is an option, but we'd like to keep what we can of what's currently installed.

Thanks!

 

[Mara]

I remember one case where was used analog output to feed voltage to NTC's and then back to analog input to measure changed voltage over ntc. There was some resistors connected in parallel with ntc and of course some math in plc. I'll try to find sample if this helps...

 

[Mickey]

Use a transmitter to convert the thermister to a 4 to 20ma output.

I would change the thermisters to a RTD or thermocouple and then use a transmitter if possible.