What does a strain gage measure?

What does a strain gage measure?

A Strain gauge is a sensor whose resistance varies with applied force; It converts force, pressure, tension, weight, etc., into a change in electrical resistance which can then be measured. When external forces are applied to a stationary object, stress and strain are the result.

What is strain gauge and types?

The strain gauge is a passive transducer that converts the mechanical elongation and compression into the resistance strain. It is invented in 1938 by Arthur Claude Ruge and Edward E. In the geotechnical field, the strain gauges are the important sensors. ...

How do you measure strain?

For strain, micrometer per meter (μm/m = 10-6 m/m = ppm) is generally used. There are several different types of gauges and sensors that can be used to measure strain. Strain gauges are the most common devices used.

What is strain gauge equation?

If the nominal resistance of the strain gauge is designated as RG, then the strain-induced change in resistance, ∆R, can be expressed as ∆R = RGGFε. Assuming that R1 = R2 and R3 = RG, the bridge equation above can be rewritten to express VO/VEX as a function of strain (see Figure 4).

How do you interpret strain gauge data?

Therefore, to measure the strain, you have to accurately measure very small changes in resistance. For example, suppose a test specimen undergoes a strain of 500 me. A strain gage with a GF of 2 exhibits a change in electrical resistance of only 2 (500 x 10-6) = 0.1%. For a 120 Ω gage, this is a change of only 0.12 Ω.

How accurate are strain gauges?

Strain meters/ digitizers have typical resolution/ precision of about ±1 x 10^-6 mm/mm (±0.0005 mV/V bridge output). Thus using four active gauges ('arms') provides benefits in precision (and accuracy) when measuring small strains.

How many strain gauges are there?

Strain gauge transducers usually employ four strain gauge elements that are electrically connected to form a Wheatstone bridge circuit. The Figure 1 shows a typical strain gauge diagram. A Wheatstone bridge is a divided bridge circuit used for the measurement of static or dynamic electrical resistance.

What are the two types of strain gauge?

Different Types of Strain Gauge Geometries

• Linear Strain Gauge. A linear strain gauge is used to record strain in the direction in which its measuring grid is aligned. ...
• Shear Strain Gauge. ...
• Rosette Strain Gauge. ...
• Chain Strain Gauge. ...
• Full-bridge Strain Gauge.

How do you size a strain gauge?

1. Geometry of the Strain Gauge. Linear strain gauges (e.g. LY4) have one measuring grid and measure the strain in one direction. Linear strain gauges (e.g. LY4) have one measuring grid and measure the strain in one direction.

How do you read a strain gauge?

Therefore, to measure the strain, you have to accurately measure very small changes in resistance. For example, suppose a test specimen undergoes a strain of 500 me. A strain gage with a GF of 2 exhibits a change in electrical resistance of only 2 (500 x 10-6) = 0.1%. For a 120 Ω gage, this is a change of only 0.12 Ω.

What is the purpose of a strain gauge?

• Such a device is called a strain gauge. Strain gauges are frequently used in mechanical engineering research and development to measure the stresses generated by machinery.

How does a strain gage work?

• As its name implies, a strain gage detects strain changes -- on everything from plane wings in a testing environment to parts of the human body. Most strain gages measure changes in electrical resistance that occur when an object undergoes strain.

How can I calibrate a strain gauge?

• Determine R R = 2/3 = 0.667 R = 2.14/3.00 = 0.7133
• Determine+Full Scale = (F T/R)*+Full Scale = (100/0.667) = 150 psi+Full Scale = (30,000/0.7133) = 42,058 microstrain
• Determine a baseline calibration value.†‡

How does a strain gauge work?

• Principle of Working of Strain Gauges When force is applied to any metallic wire its length increases due to the strain. The more is the applied force, more is the strain and more is the increase in length of the wire. Further, as the length of the stretched wire increases, its diameter decreases.