Measuring and transmitting pressure plays a key role in system monitoring and controlling pumps/fans in order to achieve a required pressure at any given time.
A pressure transmitter transmits a measured pressure as an analogue 0/4–20 mA signal to a receiver. The pressure transmitter has a piezoelectric element, which generates an electric signal which is proportional to pressure.
The receiver is typically an electronic regulator or PLC (Programmable Logic Controller). A PLC is a small computer that is not normally able to directly measure electrical signals from a sensor.
If the piezoelectric element is connected directly to the receiver, the resistance in the wire between the two components is also measured and will give a false reading. The bias is dependent on the length of the wire and the ambient temperature.
Pressure transmitters are used to avoid voltage loss or when a regulator or PLC cannot directly measure the signal from a resistance sensor.