Piezoelectric pressure sensors

Piezoelectric pressure sensors

The main advantages of piezoelectric sensors are robustness and low power.

The sensing elements are made of rigid materials, which can be natural crystals such as quartz or specially formulated ceramics. These require only a very small deformation to generate an output, so there are effectively no moving parts.

This means the sensors are extremely robust and suitable for use in a range of very harsh environments. They can also tolerate very high temperatures; some materials can be used at up 1,000ºC.

This makes piezoelectric sensors suitable for applications such as measuring pressures in jet engines.

The sensor elements are self-powered so they’re intrinsically low-power devices. It also means they’re insensitive to electromagnetic interference.

However, designing the electronic interface is more complex than the other sensor types. A charge amplifier is required to convert the very high impedance charge output to a voltage signal. This needs to be located close to the sensing element.

Some sensors include integrated electronics, which simplifies the use of the sensor but reduces the operating temperature range.

With ceramic materials, a usable output can be obtained with very small displacements. This means they can be used for measuring a very wide range of pressures, between 0.1 psi and 10,000 psi (0.7 kPa to 70 MPa), with very high accuracy.

The piezoelectric elements can be very small with an extremely fast response to changes in pressure. Some devices can measure rise times in the order of 1 millionth of a second. As a result, piezoelectric sensors are used for measuring pressure changes in explosions.

The sensors are simple to construct and can be made from inexpensive materials.

The main limitation of piezoelectric sensors is that they can only be used for dynamic pressure measurement.

The sensors are sensitive to vibration or acceleration, which may be common in the applications where they are used. This can be minimised by using an extra “compensation” sensor attached to a dummy mass. The output from this is used to correct for acceleration experienced by the sensor.