A pressure transducer is really a type of sensor that is able to recognize a change in pressure and create an electrical output that allows the system to read that change. In some instances, a transducer can also result in a mechanical output, which would create the desired change to bring a system back into balance or otherwise trigger an action within the system without the need for manual control.
With different types of pressure measurements and devices required based on the application, different types of transducers have been developed throughout the years. Each offers benefits in use and design that make it more appropriate for a specific application.
Diaphragm
With a diaphragm type of pressure transducer there are two styles, one that is metallic and one that is a non-metallic or a slack diaphragm. The second style is rarely used, with the metallic type much more common.
The diaphragm transducer is typically used only for low pressures. The common metallic types offer significant levels of elasticity that allows for measurements even with very slight pressure differentials.
As the name implies, a diaphragm is stretched across the transducer. When pressure is applied to one side of the diaphragm it moves, creating a measurable change that is translated into an electronic signal. Once the pressure differential is removed, the diaphragm springs back into place.
Bourdon Tube
For high ranges of measurements, the Bourdon tube type of pressure transducer is the most commonly selected. In this case, the tubes, which are elliptical in cross section, respond to pressure by going from a flattened state back into the circular or elliptical form.
These are incredibly durable types of transducers, and they can be used in any type of measurement requiring atmospheric pressure measurements. They cannot be used to measure against absolute pressure, but they are ideal for measuring liquid pressures in pumps and other types of pressurized systems.
Bellows
Bellows are used to measure very slight variations in pressure, and they use a series of cascading diaphragms. The exterior of the sensor is typically made from a solid metal or a series of metal rings welded together. The interior of this type of measurement device is typically sealed.
Bellows types of tranducers can be used in aircraft to measure speed, rate of climb as well in altimeters. Highly accurate, these types of transducers can be designed specifically for the application and to measure the desired range of pressure change.
There are other types of transducers used to measure pressure changes as well. Piston types, Bell gauges and electronic sensors are also commonly used in a wide variety of applications.