Control systems may have many types of circuits. The two primary circuits used in process are discrete and analog circuits. Discrete circuits are normally on or off and have a discrete response matching to buttons and switches. Analog circuits may be current based with 4-20 mA or voltage based with 0 to 10 V.

In this episode of Control Intelligence, written by contributing editor Tobey Strauch, editor in chief Mike Bacidore discusses how to troubleshoot 4-20 mA circuits.