Strain Gauge

When force is applied to a body, stress and strain are created. Stress represents the body's internal resistance to force, and the strain actually represents the displacement and deformation of the body. They are made of nickel copper wires and are glued back and forth on durable plastics. The dimensions of strain gauges are from a few millimeters to a few square centimeters and have a resistance of several tens to several thousandths of an ohm. Strain gauges are widely used in measuring pressure, weight in the load cell, torque in the crack meter, as well as position sensors. Paul Watson Bridge is used to measure the resistance changes of the strain gauge sensor.

The strain gauge can be connected in the Watson Bridge circuit as four (full bridge) and two or (half bridge) or less for example (quarter bridge) and .... In the single-pole model, it is completed with the help of an accurate resistor, and by stimulating a direct power supply, the connected voltmeter according to the following circuit image measures the zero potential difference. When stress is applied to the strain gauge, the resistance changes and instability occurs in the Watson bridge, which causes the millivolt signal to be generated and measured at both ends of the voltmeter. With the help of electronic equipment, this voltage is amplified to 5 to 10 volts, suitable for measuring, displaying and recording data systems such as data acoustics, etc.

Most manufacturers of strain gauges produce this sensor element according to their application in different patterns. Peripheral equipment including special glue and preparation materials, connection tags, cables, etc. are also part of the products of these companies.

Connecting a strain gauge requires skills and tips that can be gained in practice and experience

These should be taken into account when choosing a strain gauge.

1. Gage factor is high (low strain causes large changes in resistance)
2. High stability, linearity and low waste
3. Less sensitive to environmental factors such as temperature
4. Its physical size and mass should be small
5. The occupied surface should be small so that a point strain can be approached
6. Strain gauge resistance is low but strain sensitivity is high
7. The relationship between resistance changes and strain changes is linear