A transmitter is a device which senses a process variable, convert it into a standard signal and transmit that signal to a monitor or a controller. Simply transmitter convert signal into 4 to 20 mA current signal. It is used to create a standard signal proportional to a process variable and transmit that signal from where transmitter is installed to another receiving device. Other thing transmitter do is that it maintain that 4 to 20 mA output proportional to for example applied pressure irrespective of applied power till it goes down well below require power to turn on transmitter.
The main functions of a transmitter are:
- Measure a process variable.
- To change process variable into a pneumatic or electronic signal. (3-15 psi or 4-20 mA)
- Transmitting these signal to a monitor or a controller.
The output range of transmitter is standardized to bring uniformity in construction of secondary instruments as well as to facilitate them for test and calibration purpose.
CLASSIFICATION OF TRANSMITTER:
Transmitters are classified into two depending upon working supply and output. They are
1. Pneumatic transmitter (3 to 15 psi output)
2. Electronic/ electric transmitter (SMART transmitter - 4 to 20 mA output )
3. Hybrid transmitter (Analog + SMART)
In next article i will explain each type in detail and it's calibration procedure.