Last updated on 03/02/2020
Many times the terms and definitions for pressure sensors, 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 pressure sensors and vice versa.
Use the following guide to learn the differences between these small, but important devices and the applications for each:
What is a pressure switch and how do they work?
A pressure switch is an active electromechanical device that controls the pressure in a system to ensure safety and the proper operation of a machine. Pressure switches work by opening or closing a circuit that powers a device, like a pump, when a certain pressure is reached. When the pressure in a system exceeds or drops below a given setpoint, the device will “switch,” causing it to open or close a contact to prevent under or overpressurization of a system.
Pressure switches are usually used in pressure-system applications where safety is of 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 is used to trigger a blowout preventer to reduce the pressure in the system when it reaches a preset point.
What are pressure sensors, transmitters, and transducers?
Pressure sensors, pressure transmitters, and pressure transducers, on the other hand, are also electromechanical devices that measure pressure, but instead of signaling a switch, they merely send a read-out signal of what the specific pressure value is to a remote location. Unlike pressure switches, pressure sensors, transmitters, and transducers have no inherent mechanical switching element.
Below is a graphic that explains the differences and applicative uses for pressure switches and pressure transmitters.
Thanks to third-party software, these devices prove to be much more versatile than switches. Pressure sensors, transmitters, and transducers can be used for things like measuring efficiencies of pressure systems and controlling aerospace, defense, and industrial functions, such as inlets and outlets or chemical and fuel mixtures. These devices can even act as a safety switch themselves depending on how the software is set up to control the system.
How do you choose between these three seemingly identical devices, though?
What are the main differences between pressure sensors, transmitters, and transducers?
While pressure sensors, pressure transmitters, and pressure transducers may accomplish the same goal, they are designed for use in different applications. Let’s get into more detail about each device’s specifications:
- Pressure Sensors: A pressure sensor can be either a pressure transmitter or a pressure transducer. “Sensor” is an overarching term that includes transmitters, transducers, and the sensing devices within those classifications. All transducers and transmitters are sensors, but not all sensors are transmitters or transducers.
- Pressure Transmitters: Transmitters include complex and sophisticated electronics that consist of microcontrollers, extensive software, and firmware programming. The advanced electronics along with industry approved communication protocol (i.e. HART, Modbus, Profibus, etc.) provide several adjustability features such as reranging, zeroing, and dampening. It typically outputs calibrated current in addition to a digital signal.
- Pressure Transducers:Although transducers can contain electronics and a printed circuit board, its components are far more simple and there is no software or firmware programming. It simply outputs a temperature compensated voltage or current in relation to pressure changes. As opposed to transmitters, it only outputs an analog signal. .
Cost Considerations
Lastly, when choosing between switches and sensors, you’ll want to take cost into consideration. Due to their versatility, pressure sensors (pressure transmitters and transducers) tend to be a bit more costly to produce than pressure switches. Extremely accurate and repeatable pressure sensors can cost over a thousand to two thousand dollars in certain cases whereas the most expensive switches are generally half that at most.
While pressure switches and sensors seem to achieve the same goal at first glance, they go about it in completely different ways. Pressure switches are used in systems to ensure the safety of the machine and its operators while sensors simply relay a pressure readout to a remote location. However, due to their versatility, pressure sensors, transmitters, and transducers can be used in many different applications, but they tend to cost more than switches.
For more information on pressure switches, sensors, transmitters, and transducers, read our blog post on the importance of aircraft switches and sensors, take a look at our aerospace, defense, and industrial products, or contact us directly.