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Brief explanation of a how a strain gauge diaphragm works
There are a multitude of strain gauge diaphragm types that are currently being used in the manufacture of piezo-resistive pressure transducers but they all use the same fundamental method to convert pressure into an electrical signal.
A strain gauge diaphragm typically consists of a flat circular piece of uniform elastic material which is manufactured into a variety of different surface areas and thickness’ to optimise performance at lower and higher pressure ranges. A diaphragm that is too thick will not generate enough movement for a given pressure and one that is too thin will yield under stress resulting in a change in its characteristics.
The strain gauges come in many different varieties of size, shape and material but they are basically strips of resistive material that are either bonded to or embedded into the diaphragm surface. The resistance of the strain gauge will change as the diaphragm is flexed due to the strain gauge being stretched along its length or its width depending on the radial orientation.
A very basic strain gauge diaphragm can be constructed by mounting four strain gauges onto a diaphragm surface, aligning them all in the same direction and evenly spacing them around the diaphragm’s centre. This will ensure two strain gauges will be stretched along their length resulting in an increase in resistance and the other two will be stretched along their width resulting in a reduction in resistance.
All four strain gauges are then connected together to make a loop circuit. A supply voltage is then applied across two opposite corners of the circuit and the voltage difference between the other two corners is measured with a voltmeter. Assuming all four strain gauges are perfectly matched the voltage measured will be zero with no pressure applied. As pressure is applied the voltage will start to increase as the circuit becomes unbalanced.
Related Products
Strain gauge output pressure sensors
Panel meters for measuring strain gauge inputs
Associated Topics
Are pressure transducers different to transmitters
Measure high frequency pressure changes with millivolt output transducers
Benefits of strain gauge output pressure transducers
Site Last Updated: 07/02/12
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