Digital scale components - strain gauge

A strain is the relative change in shape or size due an externally applied force. Since strain is proportional to stress once we know the strain we can compute the stress and from that the force that is being applied. Once we know the force we know the weight of the object being weighed.

So the challenge for very accurate weight measurement is to very accurately measuring the strain. And this is what a strain gauge enables. It is a foil like structure cut into a pattern so that it does the work of a long wire. When the strain gauge experiences stress the effective length of the wire increases and that causes the amount of resistance the wire offers to change. Once this change in resistance is measured the amount of stress can be calculated. And working backwards ultimately the weight of the object placed on the scale can be measured.

Though the above description makes a strain gauge sound like a simple device one can make at home but in reality it is a highly refined component that requires high quality manufacturing. The best quality digital scales such as [keyword here] utilize very high quality strain gauges. Its material must be such that for the same amount of stress the strain caused should be the same every time. And it should be able to very nearly get back to the shape it had when the stress is removed. Also the strain must be independent of factors such as ambient temperature.