Pressure sensors are used for control and monitoring in thousands of everyday applications. Pressure sensors can also be used to indirectly measure other variables such as fluid/gas flow, speed, water level/depth, and altitude. Pressure sensors can alternatively be called pressure transducers, pressure transmitters, pressure senders, pressure indicators and piezometers, manometers, among other names. Popular applications of pressure sensors are Industrial Pressure sensing, Altitude sensing, Flow sensing, Level or depth sensing, and Gas/Liquid Leak testing.

Pressure sensor measures pressure, typically of gases or liquids. Pressure is an expression of the force required to stop a fluid from expanding, and is usually stated in terms of force per unit area. A pressure sensor usually acts as a transducer as it generates an electric signal as a function of the pressure imposed.

Types of Pressure Sensor Measurements

  • Absolute Pressure Sensor – Absolute pressure sensor measures the pressure relative to perfect vacuum pressure (0 PSI or no pressure). Atmospheric pressure, is 101.325 kPa (14.7 PSI) at sea level with reference to vacuum.
  • Gauge Pressure Sensor – Gauge pressure sensor is used in different applications because it can be calibrated to measure the pressure relative to a given atmospheric pressure at a given location. A tire pressure gauge is an example of gauge pressure indication. When the tire pressure gauge reads 0 PSI, there is really 14.7 PSI (atmospheric pressure) in the tire.
  • Vacuum Pressure Sensor – Vacuum pressure sensor is used to measure pressure less than the atmospheric pressure at a given location.
  • Differential Pressure Sensor – Differential pressure sensor measures the difference between two or more pressures introduced as inputs to the sensing unit.
  • Sealed Pressure Sensor – Sealed pressure sensor is the same as the gauge pressure sensor except that it is previously calibrated by manufacturers to measure pressure relative to sea level pressure.

Pressure Sensor Technologies

  • Piezoresistive Pressure Sensor or Piezoresistive strain gauge uses the piezoresistive effect of bonded or formed strain gauges to detect strain due to applied pressure. Generally, the strain gauges are connected to form a Wheatstone bridge circuit to maximize the output of the sensor. This is the most commonly employed sensing technology for general purpose pressure measurement. Generally, these technologies are suited to measure absolute, gauge, vacuum, and differential pressures.
  • Capacitive Pressure Sensor uses a diaphragm and pressure cavity to create a variable capacitor to detect strain due to applied pressure. Common technologies use metal, ceramic, and silicon diaphragms. Generally, these technologies are most applied to low pressures (Absolute, Differential and Gauge)
  • Electromagnetic Pressure Sensor measures the displacement of a diaphragm by means of changes in inductance (reluctance), LVDT, Hall Effect, or by eddy current principle.
  • Piezoelectric Pressure Sensor uses the piezoelectric effect in certain materials such as quartz to measure the strain upon the sensing mechanism due to pressure. This technology is commonly employed for the measurement of highly dynamic pressures.
  • Optical Pressure Sensor use of the physical change of an optical fiber to detect strain due to applied pressure. A common example of this type utilizes Fiber Bragg Gratings.
  • Potentiometric Pressure Sensor uses the motion of a wiper along a resistive mechanism to detect the strain caused by applied pressure.
  • Resonant Pressure Sensor uses the changes in resonant frequency in a sensing mechanism to measure stress, or changes in gas density, caused by applied pressure.
  • Thermal Pressure Sensor uses the changes in thermal conductivity of a gas due to density changes to measure pressure.
  • Other Pressure Sensor Technologies – There are numerous other ways to derive pressure from its density (speed of sound, mass, index of refraction) among others.