transmitter literally means sender, in the world of communication, a transmitter is a device that sends radio waves through an antenna.
in the world of process control (industrial automation), a transmitter is a device that converts a signal produced by a sensor into an instrument signal that represents a parameter being measured and controlled.
typically, the transmitter output signal is a standard analog value such as 0 to 10 volts or 4 to 20 ma.
in process control, the output signal of the transmitter is equal to 0 to 100% of the physical parameter sensed in the sensor.
in a weighing system, the weight value is a physical parameter that we intend to measure, the load cell is the sensor, the output signal of the load cell has a non-standard value, the weight transmitter converts this signal to standard values and sends it to the controller (plc or pc or…) sends.
for example, a weight transmitter with a current output of 4 to 20 ma to which a load cell with a capacity of 200 kg is connected will produce 4 to 20 ma per 0 to 200 kg (0 to 100%).
there are other types of transmitters that transmit the processed value digitally, such as transmitters that have modbus, hart or ethernet communication capabilities. in these transmitters, in addition to the transmission of the process value (pv), more parameters can also be transmitted.
now that we are familiar with the transmitter and sensor, let’s take a look at the location of the transmitter (for example, pars mega weight transmitter model pm-ltd11a) in a process control system.
as mentioned earlier, the transmitter converts the signal received from the sensor into process value (pv), which represents the physical measured variable.
a controller is a device that monitors the difference between the process variable (pv) and the set point (sp).
then, according to the result of comparing pv and sp, it determines what action to take and finally produces a digital or analog signal at its output. controllers are usually a plc.