Strain sensor

Details Strain sensor Strain sensor

1989-01-27

1990-06-26

Miller, Jr., George H.

Electrical resistors

Strain gauge type

338 5, G01L 122

Patent

active

049375504

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to a strain sensor, and more particularly relates to a strain sensor which detects a strain using a mutual relationship between strain and the resistance of a non-single crystal semiconductor containing Si.
2. Background Art
As conventional strain sensors, there are known sensors in which foils or thin wires comprising Cu-Ni alloy, Cu-Ni-Al alloy and the like; crystal semiconductors; or amorphous silicons are used as thermoelectric converters.
However, the strain sensors in which foils or thin wires are used, have drawbacks such as the ratio of resistance change against strains, i.e. the gage ratio, is small, i.e. 2 to 4, so that amplifiers are required for amplification; and noise becomes large when they are used under a comparatively strong magnetic field, for example, in the range of about 1 to about 10 tesla.
On the other hand, crystal semiconductors strain sensors have a benefit that the gage ratio is large, i.e. about 100. However, they have drawbacks such as the value of resistance largely changes in accordance with the change of temperature, in addition since the change of value is non-linear, complex thermal compensation circuits are required; and crystal semiconductors cannot be used under a comparatively strong magnetic field, for example, in the range of about 1 to about 10 tesla.
Also, amorphous Si strain sensors have a benefit that the absolute value of the gage ratio is comparatively large, i.e. 20 to 40. However, they have drawbacks such as the value of resistance is liable to change in accordance with a change of the temperature since activation energy is high, i.e. about 20 meV or more; and they are easily influenced by a magnetic field, so that they canot be used in a comparatively strong magnetic field, for example, in the range of about 1 to about 10 tesla.
It is an object of the present invention to solve the above-mentioned drawbacks of the conventional strain sensors. Namely, it is an object of the present invention to provide a strain sensor, wherein the gage ratio of G is large, the change of value of resistance in accordance with a change of the temperature is small, and the strain sensor can be used under a comparatively strong magnetic field.


DISCLOSURE OF THE INVENTION

A strain sensor of the present invention consists of a non-single crystal semiconductor containing Si, wherein activation energy determined from temperature dependency of dark conductivity is less than 15 meV. The strain sensor of the present invention has characteristics such as no amplifier is required for amplification since an absolute value of the gage ratio of G is large, no thermal compensation is required since the influence of the change of temperature against the value of resistance is small, and the strain sensor is applicable to measurement of strains under a comparatively strong magnetic field.


BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an explanatory illustration of an embodiment of a strain sensor of the present invention.


BEST MODE FOR CARRYING OUT THE INVENTION

In the present description, a semiconductor containing Si represents a semiconductor which contains Si in the range of 99.5 to 1% by atom, preferably about 95 to about 50% by atom.
When the contained Si becomes less than 1% by atom, it is not preferable that a hopping conduction tends to occur. On the other hand, when the contained Si exceeds 99.5% by atom, it is not preferable that the change of the temperature tends to become large.
As components which compose the semiconductor, Ge semiconductor materials such as, Sn and the like can be used with the exception of Si. The semiconductor materials may be used alone, or two or more than two of of the semiconductor materials may be used together. Among the semiconductors, the semiconductors which contain at least either Ge or Sn are preferable, since the temperature dependency of conductivity becomes so small that no thermal compensation circuit is required, and the gage ratio becomes large.
The content of Ge and Sn in th

REFERENCES:
patent: 3186217 (1965-06-01), Pfann
patent: 4766008 (1980-08-01), Kodato
patent: 4835059 (1989-05-01), Kodato

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