Strain Gauge

The strain gauge is one of the most important tools of the electrical measurement technique applied to the measurement of mechanical quantities. As their name indicates, they are used for the measurement of strain.

What is strain gauge and its types?

Strain gauges work by measuring the change in electrical resistance across a thin conductive foil. The gauge factor (or “gage factor”) is the sensitivity of the strain gauge (usually 2). It converts the change in resistance to the change in length. Equation 1: Gauge factor equation (source).

What is strain gauge formula?

The sensor Gauge Factor GF of a strain gauge is a characteristic transfer coefficient that relates the gauge element sensitivity to strain ε relative to its change in resistance ΔR. More specifically, GF is the ratio of the fractional change in resistance to the strain (GF = (ΔR / R) / (ΔL / L) = (ΔR / R) / ε).

What is strain gauge testing?

Strain Gage Testing is the practical assessment of flexion on specific areas of a body while it is under stress. Strain Gauge Test is used to measure PCB assembly board flexion when they are tested on a Test Fixture. When PCB assemblies are tested they are set under stress due to unbalanced forces acting on the PCBA.

What is the output of strain gauge?

Signal Amplification – The output of strain gauges and bridges is relatively small. In practice, most strain gauge bridges and strain-based transducers will output less than 10 mV/V (10 mV of output per volt of excitation voltage). With a 10 V excitation voltage, the output signal will be 100 mV.

How does strain gauge measure stress?

The material stress may only be calculated from equation σ = E ε, if the elongation in the force direction has been measured and the stress state is single-axis. In the transverse direction, a strain is measured, although there is no mechanical stress.

What are types of strain?

The four types of strain are longitudinal strain, lateral strain, volumetric strain and shear strain.

What is strain range?

This range is the temperature range within which a strain gauge can be used continuously under appropriate conditions. Strain Limit. The strain limit is the maximum amount of strain under which a strain gauge can operate under a given condition without suffering damage. Fatigue Limit.

What is unit of strain?

The unit for strain in the SI (Système International) is “one” i.e. 1 ε= 1 = 1 m/m. In practice, the “unit” for strain is called “strain” and the symbol e is used. Usually, strain is in the order of um/m, i.e. 10-6, and therefore, the unit “µε” (microstrain) is most commonly used.

What is the accuracy of a strain gauge?

Accuracies of 0.5% to 1% are typical for strain gages with a measurement limit of up to 5% strain (50,000 µε). The accuracy of DIC strain measurements tends to be around 10% below 0.3% strain (3,000 µe), with higher accuracies near 1% above 3% strain (30,000 µe).

What metal is used for strain gauges?

Metal strain gauges The copper-nickel alloy is among the commonly used materials. Unlike semiconductor strain gauges, metal strain gauges change their resistance due to geometry changes. Although metals also show some piezoresistive effects, they are usually very small compared to those of semiconductors.

What are the limitations of strain gauge?

Each strain gauge has its limitations in terms of temperature, fatigue, the amount of strain, and the measurement environment. These limitations must be examined before a strain gauge is used.

Is strain gauge a transducer?

A strain gauge type transducer converts physical quantity such as load, pressure or displacement into mechanical strain on the strain generating body (elastic body), and the mechanical strain is converted into electrical output using strain gauges mounted on the elastic body.

Who invented strain gauge?

Arthur Claude Ruge Strain gauge / Inventor

What is the formula of stress?

stress = (elastic modulus) × strain. stress = (elastic modulus) × strain. As we can see from dimensional analysis of this relation, the elastic modulus has the same physical unit as stress because strain is dimensionless.

What are the methods of strain measurement?

Three methods for strain measurement are described—speckle shearing interferometry (SSI), electrical strain gages and mechanical deflectometers; they were compared to the analytical method based on the theory of elasticity.

What is called strain?

What is Strain? Strain is the amount of deformation experienced by the body in the direction of force applied, divided by the initial dimensions of the body. The following equation gives the relation for deformation in terms of the length of a solid: ϵ = δ l L.

What is state Hooke's Law?

Hooke's law states that the strain of the material is proportional to the applied stress within the elastic limit of that material. When the elastic materials are stretched, the atoms and molecules deform until stress is applied, and when the stress is removed, they return to their initial state.

What causes strain?

A strain is when a muscle is stretched too much and tears. It is also called a pulled muscle. A strain is a painful injury. It can be caused by an accident, overusing a muscle, or using a muscle in the wrong way.

What is strain and its formula?

Ans: Strain is defined as a change in the shape or size of a body caused by a deforming force. It is given by the formula. ε = Change in dimension/Original dimension = Δx/x.