Pressure Transducer

Pressure TransducerA pressure transducer is a device which converts an applied pressure into a measurable electrical signal.

A pressure transducer consists of two main parts, an elastic material which will deform when exposed to a pressurized medium and a electrical device which detects the deformation.

The elastic material can be formed into many different shapes and sizes depending on the sensing principle and range of pressures to be measured. The most common method of utilising the elastic material is to form it into a thin flexible membrane called a diaphragm. The electrical device which is combined with the diaphragm to create a pressure transducer can be based on a resistive, capacitive or inductive principle of operation.

Product Selection Guides

Choose a pressure transducer for your application with one of these product selection guides:

If you would like us to select a pressure transducer for you, then please use this form to specify your requirements.

Transducer Types

Strain Gauge

A resistive pressure transducer has strain gauges bonded or embedded into the surface of a diaphragm so that any change in pressure will cause a change in the electrical resistance of each strain gauge.

Variable Capacitance

A variable capacitance pressure transducer has a capacitive plate bonded to one side of the diaphragm and another capacitive plate bonded to an unpressurized surface in close proximty to the diaphragm. A change in pressure will widen or narrow the gap between the two plates which varies the capacitance.

Variable Inductance

An inductive pressure transducer uses the principle of inductance to convert the flexing of a diaphragm into the linear movement of a ferromagnetic core. The movement of the core is used to vary the induced current generated by an AC powered primary coil on another secondary pick-up coil.

Resonating Frequency

Other types of pressure transducer utilise the principle of the piezo-electric effect, or material structures which vary in resonant frequency with strain.

OEM Sensing Element Modules

The pressure transducer sensing elements are mainly used by original equipment manufacturers (OEM) who incorporate them into their own products (e.g. gas analysers, leakage monitoring equipment) or pressure measurement manufacturers who incorporate them into more complex pressure sensors with compensated millivolt, amplified voltage, 4-20mA current loop or digital interface outputs, which are then sold to end users and equipment integrators.

Signal Conditioned

More complex pressure transducers include an electronic circuit for rationalising the transducer output signal so that there is very little difference from one transducer to another of the same type. A temperature compensation circuit is also added to reduce the errors associated with changes in media temperature. Often the rationalised and compensated output is then converted to a standardised output signal to make it universally compatible with end users instrumentation such as readouts, analog to digital converter cards, programmable logic controllers and data acquisition cards.

Connections & Fittings

Pressure transducers are fitted with a mechanical process connector (e.g. 1/4 BSP male, 1/2 NPT male) to the front of the diaphragm, and an electrical interface connection (e.g. DIN plug, M12) on the back of the electronics housing to enable the user to easily install the pressure transducer. In the case of pressure transducers sensing elements used by pressure measurement equipment manufacturers and OEMs, the pressure transducers may only have a prepared surface for clamping, bonding or welding and a PCB with pads or pin-holes suitable for soldering.

Pressure Transducer Help

Main cause of failure

What is the most likely cause of a pressure transducer failure?

Accidentally exceeding overpressure is probably the most common cause of pressure sensor failure.  For more information see symptons and causes of pressure transducer diaphragm damage or reasons why high pressure transducers fail.

Measuring low pressures with miniature transducers

We are looking for a small pressure transducer a few millimeters in size which will be capable of measuring small water movements of a few Pa, is this possible?

Miniature diaphragm based pressure transducers are very poor at detecting very low pressures because there is insufficient surface area to generate enough movement in the sensing diaphragm to produce a strong output signal. Any signal that is achieved will have a low signal to noise ratio and will be largely susceptible to errors caused by changes in temperature.

2mV/V output for measuring hydraulic pressure to 700 bar

I am interested in a pressure transducer that has a 2mV/V output and can measure hydraulic pressure up to 700 bar. It will be supplied with an excitation voltage of 5V dc?

The IMP which has a 2mV/V output, it is low cost but has a low overpressure & burst pressure rating of 880 bar.

The TPS has a 3mV/V output, it is more robust and better suited to hydraulics, with a much higher overpressure rating of 2000 bar.

Variable Capacitance vs Strain Gauge

How does variable capacitance compare to strain gauge sensor technology?

Variable capacitance sensors offer better performance than strain gauge devices at very low pressure ranges, although they are larger in diameter and are more expensive to manufacture.

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