Transmitter

Transmitter (Tx) is a device which converts a sensor output into an analogue signal suitable for sending over long distances without significant signal loss or interference.

In the early days of process control, the standard instrumentation signal was pneumatic while today it is more likely to be an electrical signal. The standard pneumatic signal is 3 to 15 psi, and some of the standard electrical signals are 1 to 5 volts, 0 to 10 volts or 4 to 20 mA.

In process control, it is understood and goes without saying that the transmitter output range represents the 0 to 100% of the sensed physical variable. For example, the transmitter would produce an output current range of 4 to 20 mA for a measured pressure range of 0 to 250 bar (0 to 100%).

A common type of sensor transmitter signal is a 4 to 20 milliamp current loop output.