Piezoresistive Pressure Sensors vs. Capacitive Pressure Sensors – Advantages & Disadvantages

capacitive pressure sensorHaving trouble in deciding between piezoresistive and capacitive pressure sensor in your project? Here are the advantages and disadvantages of two pressure sensing technologies:

Piezoresistive Pressure Sensors

In a piezoresistive pressure sensor, the resistors are connected in a Wheatstone bridge on a diaphragm. The strain caused on the diaphragm by the pressure causes a change in the resistances. The change in resistance is directly proportional to the change in pressure.

Piezoresistive Pressure Sensor Advantages:

  • Piezoresistive sensors are less expensive compared to capacitive sensors
  • Offers high resolution measurement
  • Highly resistant to shock, vibration, and dynamic pressure changes
  • They have high electrical and mechanical stability
  • Can be used over a wide range of pressure (from 3 psi up to 20,000 psi)
  • Smaller in size and robust in construction
  • Sensors made with thin-film resistors are much more resistant to higher temperatures and overpressure.

Piezoresistive Pressure Sensor Disadvantages:

  • Piezoresistive sensors cannot function on low power or battery operation.
  • Scaling down the size of the sensor reduces resistance and increases power consumption
  • The output of the sensor is dependent on temperature variation

Capacitive Pressure Sensors

Capacitive pressure sensors measure the change in electrical capacitance as a direct relation to change in pressure. A capacitor circuit consists of two parallel conducting plates, one of which acts as the diaphragm. The diaphragm moves according to the applied pressure, thus changing the capacitance.

Capacitive Pressure Sensor Advantages:

  • Capacitive sensors have heightened pressure sensitivity and measure both high and low pressures accurately
  • They are not affected by changes in temperature, and the temperature coefficient of sensitivity of a capacitive sensor is 10 times better than a piezoresistive pressure sensor
  • Power consumption is low and does not require power source
  • Response time is also low
  • They exhibit less error, high accuracy and high reliability in measurement
  • Resistant to EMI (Electromagnetic Interference) and RFI (Radio Frequency Interference)

Capacitive Pressure Sensor Disadvantages:

  • Non – linearity, because output is inversely proportional to the gap between the parallel plates
  • Highly sensitive to vibration

Both piezoresistive and capacitive pressure sensors can be used for measuring all types of pressure. They are also compatible with any kind of media and corrosion-resistant.