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What is the difference between Pressure transmitters, Universal detectors, Pressure switches and Vacuum switches?

Pressure transmitters

Are part of a range of products more properly generically referred to as Pressure Transducers.  They modify or generate an electrical signal in proportion to the pressure sensed.

Commonly, the signal takes the form of  0-10VDC, 0-20mA DC or 4-20mA DC analogue signal.
0-20 and 4-20mA devices are also known as "Current Loop" devices and have the advantage of being able to "transmit" over very long distances, therefore often referred to as "transmitters"  rather than transducers. 0-10VDC devices are generally referred to as "Transducers".

Consideration  must be given to the fact that the environment, e.g. circuit impedance, EMI, can effect the signal received by the receiving device. The transducer controls it's output voltage very accurately but it has no way of knowing if that same voltage is seen by the receiver, so volt drops and interference can have an effect on accuracy. Current loop devices, however, will have the same current flow in all parts of the loop as well at the sensor itself, so the device is able to monitor the received signal and compensate for any outside influence, within reason.

They have a particularly robust construction and, unlike electro mechanical devices, are not adversely effected by rapid and frequent pressure changes.

Pressure switches and vacuum switches

Devices for operating a switch at a specified pressure threshold, rather that emitting a changing signal to indicate actual pressure. The majority in use today are still electromechanical, operating conventional contacts to either operate a motor or pump directly or provide a control or alarm signal to other devices.

Electronic versions are becoming increasingly popular. They provide a digital (on/off) signal at a pre determined pressure. Their high degree of repeatability and very short response times also make them suitable for very accurate and rapid pressure regulation and monitoring.

Universal detectors

Universal detectors are electronic pressure switches and/or vacuum switches that are also equipped with an analog output identical to that of transmitters or transducers.
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