Strain Measurements

The strain or deformation of materials under a certain load is measured with the help of strain gauges. Strain gauges are printed conductive tracks on a carrier substrate. Strain or compression changes the length of the trace and thus its electrical resistance. The very small change in resistance is measured with a bridge amplifier. The strain gauges are electrically connected together to form a Wheatstone Bridge. Depending on which and how many elements of the bridge are formed by an active strain gauge, it is referred to as a ¼, half or full bridge. The non-active elements are formed by constant resistors.

Strain gauges are used, among other things, for long-term monitoring of structures. In this case, the signals to be measured are rather slow (< 10 kHz). When characterizing new materials, dynamic load tests are often carried out. For example, a hydraulic press is used or the material is subjected to a blast wave from an explosion. For such dynamic tests a high bandwidth of the bridge amplifier is necessary to amplify the steep edges of the signal correctly. The Elsys strain gauge amplifier (SGA)  is ideally suited for this purpose, since it has a bandwidth of up to 1.5 MHz. In combination with a TraNET FE, precise dynamic strain measurements can thus be made.