Many times the terms and definitions for pressure sensors such as switches, transducers and transmitters are used interchangeably with disregard to the actual meanings and differences. The exact definitions do differ from source to source spurring the confusion and misuse, however, understanding the differences can help you know when to use a pressure switch versus a pressure transmitter and vice versa.

Pressure Switches

A pressure switch is an active electromechanical device which measures the pressure in a system and when the pressure reaches too high or too low of a given set point, the device will “switch” meaning it will open or close a circuit that powers a certain device (like an alarm system or a shutdown valve).

Pressure Transmitters (Transducers)

A pressure transmitter or pressure transducer, on the other hand, is also an electromechanical device which measures pressure but instead of signaling a switch, it merely sends a read-out signal of what the specific pressure value is to a remote location.

Usually a pressure switch, rather than a transmitter, will be used in pressure-system applications where safety is of a paramount importance. An oil wellhead, for example, can see some very high pressure spikes, and if the pressure reaches too high, a possible well blowout can occur. A pressure switch in this application makes sense, so that when the pressure reaches too high, the switch can trigger a blowout preventer, which can actuate to reduce pressure in the system.

In contrast, the pressure transmitter has no inherent mechanical switching element. However, transmitters prove to be much more versatile in that, via third party software that interprets the given pressure reading, they can be extremely useful for measuring efficiencies of pressure systems and can control many industrial functions, such as inlets and outlets, chemical or fuel mixtures, or can even act as a safety switch itself depending on how the software is set up to control the system.

Cost Considerations

This versatility generally comes with a cost however, as transmitters tend to be a bit more costly to produce than pressure switches. Extremely accurate and repeatable transmitters can run to as high as over a thousand dollars in certain cases, whereas the most expensive switches are generally half that.