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How to troubleshoot and calibrate 4-20 mA

Best practices for troubleshooting analog circuits to the PLC

By Mike Bacidore, editor in chief
Sep 13, 2016

A Control Design reader writes: We have several temperature, pressure and flow sensors on a new medical-device cleaning skid that we are developing. These instruments are connected to a PLC as 4-20 mA inputs, and there is also a 4-20 mA output used to control a pump motor speed. A recent failure of a flow sensor brought the process skid instrumentation to my company's quality manager's attention. He asked how we know that the temperatures, pressure and flow are accurate, and how do we know that we are cleaning properly.

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