Incompatible transducer

I am connecting a Hamilton PH probe (238999 4490) to an AB remote IO (1794-IEXT). From the probe I have the positive lead (red core) connected to C37 of the base module, I have the common (red shield) connected to B19 of the base module. I have my meter set up between the PH signal (Black core) and the base module A2 (input 1 current). I'm not seeing my 4 to 20 ma signal. I've tried several channels with the same results, and called Rockwell Automation and was suggested this transducer (must be) incompatible with this card. Any info out there on this? I have several channels on this card that are loop powered and functioning,,, this is the only device that is not loop powered.

Most pH probes are just that, sensor probes that are a high impedance sensor with a mV output.

A transmitter takes a sensor input and provides a conditioned output, like a 4-20mA signal. PH inputs are specially designed to not load the high impedance probe (with resulting error).

If the documentation for that probe does not mention 4-20mA, it probably is not a transmitter, it is most likely a pH sensor probe.

PH sensor probes need to be connected to a device that provides conditioned output, usually because that device also provides for calibration and calibration checks, which are needed quite frequently. y pH is high maintenance.

pH probes are usually connected to either a pH analyzer (digital readout, optional analog retransmit output or in some cases, a pH transmitter.

I suspect you have a pH probe and need a signal conditioning analyzer.

Thank you for your response. I found out this actually needs a different PLC card with a differential (+ and -) input.

If this is not for school or a bench top experiment, but for process monitoring, you should consider getting a pH analyzer with a 4-20mA analog output because pH needs constant calibration checks and re-calibration. Analyzers are typically setup to prompt one through the process and to save the results.

If you use a high impedance differential AI card in a PLC, you'll have to develop the means and method to check and/or re-calibrate the pH probe.

If you have to buy something to make it work, you might consider getting something that fits the nature of beast, and pH is beastly (high maintenance.)