Metal Foil Strain Gauges
In this type of strain gauges a metal foil is used to sense the applied strain.
The materials used for its construction are nickel, nichrome, platinum, isoelastic (nickel + chromium + molybdenum), constantan (nickel + copper).
The gauge factor and characteristics of foil strain gauges are similar to the wire strain gauges. be easily etched on a the metal foil gauges can flexible insulating carrier film.
In the construction of etched foil strain gauge first a layer of strain sensitive material is bonded to a thin sheet of backelite or paper.
The part of some masking material and then to this unit an etching solution is applied.
Therefore, the unmasked part of the metal will be removed thereby leaving the required grid structure.
By this method of construction, the etched foil strain gauges are made in thinner sizes.
Different forms of metal foil strain gauges are:-
When a force or pressure is applied to the sensing element of metal foil strain gauge the physical dimensions of it will change.
Since, the strain gauge element is pasted on its surface, the dimensions of the strain gauge changes due to which the resistance of the gauge changes.
The measure of change in resistance will become the measure of applied pressure or force (this change in resistance of the gauge can be measured by connecting the gauge in any one of the four arms of balanced Wheatstone bridge).
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