Semiconductor strain gauge

Semiconductor strain gauge:

A typical semiconductor strain gauge is formed by the semiconductor technology i.e., the

semiconducting wafers or filaments of length varying from 2 mm to 10 mm and thickness of

0.05 mm are bonded on suitable insulating substrates (for example Teflon). The gold leads are

usually employed for making electrical contacts. The electrodes are formed by vapour

deposition. The assembly is placed in a protective box as shown in the figure below.

The strain sensitive,elements used by the semiconductor strain gauge are the semiconductor materials such as, silicon and germanium. When the strain is applied to the semiconductor element a large of change in resistance occur which can be measured with the help of a wheatstone bridge. The strain can be measured with high degree of accuracy due to relatively high change in resistance.

 A temperature compensated semiconductor strain gauge can be used to measure small strains of the order of 10-6 i.e., micro-strain. This type of gauge will have a gauge factor of 130 ± 10% for a semiconductor material of dimension 1 x 0.5 x 0.005 inch having the resistance of 350 Ω.

Advantages of Semiconductor Strain Gauge:-

1. The gauge factor of semiconductor strain gauge is very high, about ±130.

2. Semiconductor strain gauge exhibits very low hysteresis i.e., less than 0.05%.

3. They are useful in measurement of very small strains of the order of 0.01 micro-strains

due to their high gauge factor.  

4. The semiconductor strain gauge has much higher output, but it is as stable as a metallic

strain gauge.

5. It has a large fatigue life i.e., 10 x 106 operations can be performed.

6. It possesses a high frequency response of 1012 Hz.

7. They can be manufactured in very small sizes, their lengths ranging from 0.7 to 7.0 mm.