The Complete Guide to Industrial Level Sensors

Level measurement is one of the most common parameters measured in process industries. Level sensors use one of several principles to detect the level of liquid in a container and convert the measurement to electrical signals or a mechanical movement for local indication. Some of the types covered in this article include visual detection, capacitance, conductivity and ultrasonic type level sensors. 

This is a companion discussion topic for the original entry at

I have 4 control valves with Siemens SIPART valve positioner, connected to Allen Bradley control logix analog output module, when the PLC is powered on everything comes up with the analog output module showing green light and ok after 4 hrs , The analog output module begin to show a red alarm and thereby putting the control valves power off

The analog output module was replaced, and everything seems to be ok, but after 5 days the analog output module LED went back to Red alarm, and put off the control valves power.

Please could this be software issues or earthing issues