Extensometers for materials testing
Frequently Asked Questions
Can Epsilon extensometers be left on through specimen failure?
Yes. All Epsilon standard extensometers are designed to withstand remaining on the sample though specimen failure with most materials. On certain materials, such as high strength metals, knife edges will wear out faster if the extensometer is left on through failure. A spare set of knife edges is included.
In the following applications, we recommend removing model 3542 and 3442 extensometers before specimen failure, or using an Epsilon ONE® non-contacting extensometer:
- Rebar and other materials with textured or rough surface finishes (note: use model 3543 or Epsilon ONE to test through failure with rebar)
- Wire cable
- Unidirectional composites and similar materials that explode / disintegrate at failure
- Non-rigid griping systems such as “lever action” wedge grips with moveable grip faces or grips with spherical seats
- Long samples of elastic material
- When the expected elongation of the material exceeds the extensometer’s designed measuring range (for example, using an extensometer with a 10% measuring range with a metal specimen that is expected to reach 20% elongation)
- Rupture of internally pressurized specimens
Will the extensometer be compatible with my existing electronics?
The majority of Epsilon’s extensometers are strain gaged transducers which may be connected to most brands of materials testing controls. If your controls have the signal conditioning module for a strain gaged extensometer, we can supply the unit with the necessary connector to plug in directly. If you are using a data acquisition board to acquire test data, the extensometers can almost always be interfaced properly. A few of our extensometers use capacitive sensing technology, and these include the required electronics.
If your controls are designed for LVDT type extensometers only, we can provide the electronics to work with our extensometers. Available electronics are covered here. This is also ideal for older test machines, which may not have any extensometer electronics, allowing the output to run a chart recorder or plotter, or interface to a data acquisition board.
The Epsilon Shunt Calibration System, included with all Epsilon strain-gaged extensometers, helps make on-site customer calibration of the electronics and extensometer quick and easy. It also allows you to send your extensometer back to Epsilon for periodic re-calibration. The VREF provides the same calibration function for Epsilon’s capacitive extensometers. Click here for further details about shunt calibration.
What electronics are needed?
How do I decide what measuring range I need?
Generally speaking, Epsilon’s extensometers will meet the higher levels of accuracy requirements in today’s standards, such as ASTM E83. You can thus be assured that reasonably accurate measurements at the low end of the range can still be made.