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Strain Gauge Structure And Principle
Dec 21, 2017

Strain gauge construction
There are many types of strain gauges. A typical strain gage is to affix a sensitive grid (3-6μm) made of a thin metal foil on a plastic film (15-16μm) called the base and then covered with a thin film to form a laminate.

Strain gauge principle
The strain gauge is attached to the object to be measured, so that it expands and contracts along with the strain of the object to be measured so that the metal foil in the object stretches or shortens with strain. Many metals change their resistance when mechanically stretched or shortened. Strain gauge is the application of this principle, measured by measuring the resistance of the strain change was measured. Strain gages generally use the sensitivity of the copper-chromium alloy, the resistance rate of change is constant, and the strain is proportional to the relationship. which is:

Among them, R: Strain gauge original resistance Ω (ohm)
ΔR: resistance change due to elongation or compression Ω (ohms)
K: Proportional constant (strain gauge constant)
ε: Strain
Different metal materials have different proportional constants K. Copper-chromium alloy K value of about 2. In this way, the strain measurement is converted by the strain gauge into a measure of resistance change. However, since the strain is a relatively small change, the resulting change in resistance is also extremely small.
To accurately measure such a small resistance change is very difficult, the general resistance meter can not meet the requirements. To measure this small change in resistance, we used a dedicated strain gauge with a Wheatstone bridge.

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