Pressure sensor vs pressure transmitter – are they the same thing?

Pressure sensor

A sensor is a device or component that is in physical contact with the variable being measured, in this case pressure. It detects changes in environmental parameters and provides a corresponding output signal that can be measured.

An example of a sensor is a mercury glass thermometer. The input signal is the temperature, influenced by changes in which the liquid in the thermometer contracts or expands. This causes an increase or decrease on the indicator, which is readable by humans.

If the sensor does not provide meaningful output data on its own, it must be part of a transmitter that converts it into a comprehensible format.

What is pressure transmitter? Difference between sensor and transducer

A transducer, in general terms, is a device that converts one form of energy into another. The output quantity is usually an electrical or electronic signal.

A pressure transducer measures pressure and converts the physical attributes of this non-electrical signal into an easily measurable current (e.g. 4-20 mA) or voltage (e.g. 0-10 V) signal. The output signal is linear and proportional to the set pressure.

Depending on the type of pressure being measured, we distinguish between:

• relative pressure transducers

• absolute pressure transducers

Pressure transmitter – construction

Pressure transducers consist of a sensor and electronic circuits that convert the input signal into an equivalent electrical form and provide it with sufficient power for further processing.

There is no other, separate name for these two, combined devices, hence the confusion in naming - some call this pair a sensor and others a pressure transducer.

Transducers and transmitters – differences

Both transducer and transmitter, transform energy from one form to another and give output signal. This signal is routed to a device that interprets it. Transmitters and transducer are almost the same. It differ only differ only in the type of signal emitted by each of them. Transducer sends a signal in volts (V) and transmitter in miliampers (mA).

When to use switches and when to use pressure transmitters?

There is also much doubt about the distinction between switches and pressure transmitters.

Pressure switch

A pressure switch is a device that consists of a transducer and an electrical switch. As we discussed above, the transducer produces a current or voltage signal representing 0-100% of the physical process pressure. The pressure switch has electronic contacts that close or open when the set pressure is reached.

Pressure switch as a separate device or integrated with a pressure transmitter?

Switches can be a separate device or occur as a function of the pressure transmitter. The choice of the optimal solution depends on the characteristics of the application. Often electronic pressure transmitters with a switching function, such as DELOS SI, provide cost savings by reducing the number of measuring points and products used.

Pressure switch – application examples

Pressure switches are used in, among other things:

• compressed air systems – they switch the compressor on/off when a predefined value is reached

• pumping systems - switches the pump on/off to maintain the desired water level in the tank

• process equipment - pressure switches are used to maintain a constant flow of fluid in the equipment