What are strain gauges

Strain gauges are electronic components developed to measure (the degree of) strain on an object. Strain gauges consist of a foil with an electrical conductor on it. When strain gauges are stretched also deforms the electrical conductor. This causes a change in resistance.

The theory behind strain gauges

The relationship between the change in length (strain) and the change in resistance is linear within practical limits. The factor that indicates this is called the sensitivity factor or k-factor. The k-factor is approximately 2.0 for most strain gauges and is always stated on the packaging of the strain gauges.

In formulas:
relative resistance change = sensitivity factor x relative length change.
∆R/R = kx ∆L/L (the relationship is dimensionless).

Because the relative resistance change to be measured is very small, it cannot be measured accurately with an Ohmmeter. For this purpose, the strain gauge is placed in a Wheatstone bridge. To simplify the notation, the relative length change is expressed in µm/m or µrek (0,000001 m/m).

Example:
set relative length change of 1 µ/m.
relative resistance change = kx 1 µ/m = 0,000002
absolute value at 120 Ohm strain gauge = 120 x 0,000002 = 0,00024 Ohm.
absolute value at 350 Ohm strain gauge = 350 x 0,000002 = 0,00070 Ohm.

Dexman

We at Dexman know better than anyone that the right information is the most important thing. Because if a measurement is not correct, the solution is of no use to you. This applies not only to the solutions we offer, but also to the way in which we communicate. At Dexman, we stand for quality, service and solution orientation. In this, it is important to provide the right information, offer a good solution and be honest with each other.

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