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High density RTD/resistance input cards

High density RTD/resistance input cards

High density RTD/resistance input cards

Hello, I am looking for an analog input card or device that measures resistance, and interfaces with an Allen-Bradley PLC, preferably using Ethernet/IP. The measurement repetition rate should be less than 500ms or so, ideally less than 100ms. Resistance range is about 50-500Ω. We need 48 channels, so high density is valued. 12-bit resolution should be sufficient. What options are out there?

I have explored the brands Wago, Allen-Bradley, Advantech, B&R, and Beckhoff so far, but each of their solutions has various drawbacks.

I am open to using a voltage input card, but the full scale range would need to be around 200mV, not the standard 10V. And plus going that route would require pull-up resistors, complicating the panel wiring.

RE: High density RTD/resistance input cards

Thanks for the quick response IR. Looks like that Keithley solution is close, but it looks like it does not offer any industrial comms protocols such as Ethernet/IP, Profinet, Modbus/TCP, etc. This needs to interface directly with an Allen-Bradley PLC.

RE: High density RTD/resistance input cards

Spectrum Controls has a line of analog input modules for Control and Compact Logix controllers. I use 1756-IF8Usc and 1769-IF8Usc with good success.

Brad Waybright

The more you know, the more you know you don't know.

RE: High density RTD/resistance input cards

Acromag's busworks series is modular I/O with preloaded comm protocols (including Ethernet/IP) in the bus network module.

The 6 minute video is a good summary:

voltage input modules on this page:

I didn't read closely enough to see if the RTD resistance input module would do 2 wire raw resistance over your range, but most I/O modules do.
temperature (resistance) modules on this page:

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