Field Transmitter Principle

The major purpose of a transmitter is to measure a change in process variable from a remote location and to transmit it at required location. Transmitter is a device (electronic/pneumatic) which measure a process variable and converts it into standard, proportional signal. Standard signal can be pneumatic or electronic

Pneumatic signal is 3 to 15 psig while electronic signal is 4 to 20 ma. Transmitter has a supply of 24vdc for electronic and 20 psig for pneumatic

Principle of operation

The transmitter consist of a sensor part and a processing part. The sensor part create a primary change proportional to the process variable’s change. The processor part convert that change into a standard ouput signal. For example:

A process variable e.g pressure can be varied from 0 to 100 psig and we want to measure it and also we want to transmit it to a remote location. Then first off all range of transmitter is set to our required value (o to 100 psig). Then we will apply process variable at different values as 0%, 25%, 50%, 75%, 100%. The transmitter will generate a proportional out put as 4mA, 8 mA, 2 mA, 16mA, 20 mA or if we use pneumatic transmitter 3 psig, 6psig, 9psig, 12 psig, 15 psig respectively that out put signal can be transmitted to a remote location either it is electronic or pneumatic.