Using Strain Gauges

Concept of Strain Gauges

A strain gauge is a device used to measure the strain (deformation) of an object. The object’s deformation is a measure of how much it is stretched or compressed when a force is applied.
Strain gauges are based on the property of electrical conductance and resistivity. When a metal is stretched, its length and cross-sectional area will change, altering its resistivity.

How Strain Gauges Work

When a force is applied to an object, the object deforms. This deformation changes the shape, and hence the resistivity, of the strain gauge which is attached to the object.
As the resistivity of the strain gauge changes, the electrical current flowing through it also changes. This change in current can be measured and used to calculate the amount of strain on the object.
The strain gauge is typically attached to the object using a special type of adhesive. This ensures that any deformation in the object is transferred directly to the strain gauge.

Types of Strain Gauges

Foil strain gauges are the most common type. A small strip of metal foil is arranged in a grid pattern. The changes in the resistivity of the foil reflect the strain experienced by the object.
Semiconductor strain gauges operate on the same principle but can detect much smaller changes in strain. They are, however, more sensitive to temperature changes.

Applications of Strain Gauges

Strain gauges have many applications in engineering, research and industry. They can be used to test materials for their properties, verify designs and structures, and monitor buildings and bridges for safety.
In the medical field, strain gauges are used in devices that monitor bodily functions, such as breathing and heart rate.

Challenges in Using Strain Gauges

One challenge in using strain gauges is dealing with their sensitivity to temperature. Changes in temperature can cause the metal in the gauge to expand or contract, affecting the readings.
A common solution to the temperature problem is to use a compensation technique. This involves placing a dummy gauge on a piece of metal with no strain. Any apparent change in strain from this dummy gauge is then subtracted from the actual readings of the main gauge.