Despite the state-of-the-art extensometers in use today, the use of strain gages in materials testing is still very much a current issue. These measuring components, which were developed independently by Simmons and Ruge in the 1940s, are used both to determine material characteristics and for component testing.

They function on the principle that a metal wire changes its resistance in proportion to deformation. In this way, a Wheatstone bridge circuit is used to measure deformations on a scale of μm/m (1 μm/m = 0.0001%).

With a Zwick materials testing machine operated with testControl and testXpert^® II, there are several possibilities for achieving synchronous integration of these strain gage signals.

1. Direct connection to testControl

Various strain gages (120Ω, 350 Ω, etc.) with different circuitry (1/4 or 1/2 bridge) can be connected directly to the measurement and control electronics via a series box.

Few measuring points use this solution. As well as straightforward connection, we should also point out that the materials testing machine can be controlled in line with the strain gage signal.

2. Connection via HBM  measurement amplifier

The MGC+ and Spider measurement amplifiers supplied by HBM offer all the options for measuring high-resolution electrical signals (also strain gages). These measurement amplifiers are connected to testXpert® II synchronously via a special interface. This is the simplest method for achieving a  multiple measurement arrangement.

3. Connection via a National Instruments measurement amplifier

NI USB-6009 and NI USB-6229 measurement amplifiers are integrated in the current testXpert^®  II V3.3. These amplifiers, which cover 8 or 16 analog channels, can also be synchronously connected. In the solutions presented here, all signals are recorded and processed in testXpert^® II synchronously. The user only has to deal with a simple, familiar software environment. Zwick offers a flexible solution that suits every application, which integrates electrical signals from strain gages in your test results.