Transducer
A transducer is a device that converts one form of energy or physical quantity into another, most commonly converting a physical measurement such as pressure or temperature into an electrical signal. In automation it is the element that makes a process variable readable by control and monitoring systems.
Transducers underpin nearly all industrial sensing: a pressure transducer turns force per area into a voltage or current, a load cell turns mechanical strain into an electrical output. The term is sometimes used broadly to include actuators that convert signals back into physical action. Transducers matter because they form the bridge between the physical plant and digital control systems, and their accuracy, repeatability, and stability directly determine measurement quality.
How a transducer produces a measurement signal
In industrial measurement, a transducer converts a physical input into a signal that an instrument can read. For example, pressure can deflect a diaphragm. A strain-gauge bridge converts that movement into an electrical change. The measurement system then converts the signal into pressure units.
Pressure transducers also use capacitive and piezoelectric sensing. An unconditioned bridge sensor needs excitation and suitable signal conditioning. An amplified sensor includes some of that circuitry.
Source: NI: pressure sensors and signal conditioning.
Transducer and transmitter: check the output
Supplier terminology varies. WIKA uses “pressure transmitter” for a pressure sensor with standard electrical and mechanical interfaces and a standard output. Its electronics condition the sensor signal, including amplification and temperature compensation. A 4–20 mA output is one example.
Check the device output and supply requirements against the receiving instrument. The product name alone does not establish compatibility.
Source: WIKA: pressure transmitter terminology.
Checks before selecting a measurement input
Use the device data sheet and the input-module specification together. Check the measured quantity and range, output type and scaling, power or excitation, signal conditioning, calibration and operating conditions.
For pressure, identify whether the reading is absolute, gauge or differential. These references are not interchangeable.