to check the difference between sensor, transducer and transmitter, we must first check the meaning of each of them.
sensor: a sensor/device that detects or measures a physical property and records, displays, or otherwise responds to it.
transducer: it is a converter/device that converts the changes of a physical quantity such as pressure or brightness into an electrical signal and vice versa.
transmitter: as described in the article “what is a transmitter?” we said that the transmitter is a set of equipment used to produce and transmit electromagnetic waves carrying messages or signals, especially radio or television waves. such as pm-lt11a
now that we are familiar with the meaning of each, let’s take a look at the application of each in industrial automation and precision instruments:
a sensor is a device that senses the desired physical changes and produces an output signal according to the changes. such as rtd temperature sensors, thermocouples and strain gauges.
transducer or converter is a tool that converts one type of energy into another type, in the field of instrumentation, it is the output of an electrical signal. in fact, it measures pressure, power, temperature, etc. and creates an electrical signal accordingly.
with the definitions and examples above, it can be said that all sensors are a subset of transducers, but not all transducers are sensors.
to better understand the basic explanation of the transducer, a pressure sensor converts mechanical energy into electrical energy, so it can be classified as a transducer, and a speaker converts electrical energy into mechanical energy (sound), so it can be said to be a transducer, but it is not a sensor.
and the transmitter:
the transmitter is used as a measuring and intermediate signal conversion device. in fact, it amplifies and transforms the signal received from the sensor. then it produces the output signal with the ability to transfer to the control or display device.
in other words, a transmitter is an intermediate signal converting device that is usually used to measure physical parameters such as pressure, temperature, level, current, etc.
consequently, the difference between sensors, transducers and transmitters is in the type of signal they convert and also in their application in industrial automation and instrumentation. sensors are used to detect and measure desired physical changes. transducers are used to convert physical changes into electrical signals. and the transmitters are used to amplify and convert the intermediate signal into a signal that can be transferred to the control device (plc) or display (hmi).