Sensor, transducer and transmitter, what’s the difference?

Sensor

A sensor measures a physical quantity (such as temperature, light or magnetic field) and converts it to a readable output. However, ‘readable’ don’t always mean ‘useful’. A common output is a change in resistance.

Transducer

A transducer converts one form of energy to another. In this context, the transducer is the signal conditioning. Thus, the transducer transforms the readable output into a useful output signal, for example, from 0-10V.

Devices that contain both a sensor and signal conditioning?

Most devices contain a sensor and signal conditioning, should the device be called a sensor or a transducer? By definition, it’s both; the term used depends on the context and the manufacturer. In the context of position measurement, the device is commonly referred to as a sensor, but the term transducer is also used. In the context measuring pressure, level, flow, etc., ‘transducer’ is the preferred term. ‘Transmitter’ is another term used in this context.

Transmitter

One definition is that pressure transducers do not apply any signal conditioning while a pressure transmitter apply conditioning. Therefore, a pressure transducer is a pressure sensor including mechanical housing and electric connector. Trafag uses this definition, all devices that apply signal conditioning are termed ‘pressure transmitter’.

Transducer vs Transmitter

Another commonly used definition is that a transducer only amplifies the signal from the sensor, while a transmitter converts the signal. An mV output from the sensor is amplified to 0-5V, 0-10V etc., output in a transducer. A transmitter converts the output signal to, for example, 4-20 mA or a digital output such as CANopen.

The term ‘transmitter’ is rarely used in the context of position sensors.

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