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What is the difference between strain gauge and capacitive transducers?

May 25, 2017

Thin Film Sensor Diagram as an example of a capacitive transducerSetra is best known for pioneering the variable capacitance principle, the technological innovation behind capacitance-based pressure transducers. Variable capacitance transducers demonstrate industry-leading accuracy especially in low pressure HVAC and critical care applications with accuracies as high as ±0.25” water column (±0.009 PSI).

But while Setra may be known for variable capacitive transducers, there is another viable pressure sensing technology we use for some industrial and OEM products – strain gauge.

What is a strain gauge sensor?

During the manufacturing process, a mechanism is built upon the backside of the transducer’s sensing diaphragm. Through a sputtering process, a small circuit is created that contains on it a Wheatstone-bridge resistance network. As pressure is applied to the diaphragm and unbalances (or strains) the bridge, its electrical resistance is changed and results in a voltage output.

This is comparable to capacitance transducers, where pressure flexes the diaphragm away or towards an electrode, changing its capacitance and converting it to a voltage or current. So why would one choose a strain gauge sensor over a capacitive one in an industrial application? Or vice versa?

Benefits of Strain Gauge Sensors

  • Excellent resistance to shock, vibration, and dynamic pressure changes
  • Measurement cell is hermetically sealed and does not require additional sealing materials
  • Economical to manufacture

Benefits of Capacitive Sensors

  • Better for applications that are susceptible to over-pressurization
  • Very good hysteresis, linearity, stability, and repeatability, in addition to static pressure measurement capability
  • Excellent accuracy in low pressure ranges – as low as 1 PSI.

Not sure what kind of transducer your project needs? CLICK HERE to get in contact with one of our application engineers today. 

Topics: General Industrial OEM, General Industrial