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The Strain Gauge Structure
Nov 02, 2017
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The strain gauge structure

There are many kinds of strain gauges. The common strain gage is a sensitive gate (3-6μm) made of thin metal foil on a plastic film called a substrate (15-16μm), and then covered with a layer of film to make an overlay structure.


Classification of strain gauges

According to the material: metal type--wire, foil type, film type;

Semiconductor Type-film type, diffusion type, epitaxial type, pn knot type by structure: monolithic, double, special shape according to use environment: high temperature, low temperature, high pressure, magnetic field, underwater;

Main Features:

1. part of the strain plate has the self compensation function, does not need to compensate the piece, itself can restrain the function of the strain temperature drift.

2.product variety, can give customers in different measurement occasions, to provide perfect strain measurement options, mainly: Ordinary, low-temperature, high-temperature, ultra-high temperature waterproof, composite materials, concrete, welding, welding waterproof, semiconductor, measuring residual stress, such as very perfect product specifications and models.

3. Wide range of measuring temperature: -269℃-800℃

4. Good product stability, long time measurement, product measurement results are stable.

5.the Product measurement shape is diverse, can measure a variety of mechanical signals, such as: measuring torque, shear stress, concentrated stress, and so on.


Strain gauge principle

The strain gage is affixed to the measured object to expand with the strain of the measured substance, so that the metal foil is stretched or shortened with strain. Many metals will change in their resistance when they are mechanically stretched or shortened. The strain gage is used to measure the strain by measuring the change of resistance. The sensitive grating of the general strain Gage is made of copper-chromium alloy, and its resistance change rate is constant, and it is proportional to strain. That:

R--------Strain Gage Original resistance value Ω (ohm)

ΔR------Resistance changes caused by elongation or compression ω (ohm)

K--------Sensitive coefficient of strain gage (constant, supplied by manufacturer of strain Gage)

ε--------Strain

Different metal materials have different proportional constants K. The k value of Cu-Cr alloy is about 2. In this way, the strain measurement is transformed by a strain gage into a measurement of the resistance change. However, because the strain is a very small change, the resulting resistance changes are also extremely small.

It is very difficult to accurately measure such a small resistance change, and the general resistance meter cannot meet the requirements. In order to measure the change of the micro resistance, we use a special strain measuring instrument with Wheatstone power Bridge.