Monitoring the temperature facilitates predictive maintenance schedules. Speed and motor current are used in motor control and may also be used to provide safety shut down. The sensors that are used to monitor these variables produce very different signals. Proximity sensors produce a frequency signal that can vary from a couple of hundred millivolts to 24 Volt amplitude pulses. Thermocouples and RTDs are used to measure temperature.
Thermocouples produce a small millivolt output.
The current has to be small to keep from heating up the element, hence another millivolt signal. Motor currents can be very large. Getting all these signals in to a control system can be problematic. Action Instruments signal conditioners provide a solution to normalize signals into a control system. Control systems that accept a 4-20 mA signal are plentiful , therefore less expensive.