They have been developed to measure axial displacements for simple performance testing of asphalt. These extensometers are usually mounted as two axial modules with independent outputs capable of measuring sample strains at two locations, but they can be mounted as one unit or up to four per sample.
The extensometer is equipped with magnets at all ends. The magnets at each end of the extensometer snap instantly onto the steel test points glued to the test piece. The quick clamp is especially useful when testing preheated or chilled specimens. This is because extensometers can be installed before significant temperature changes occur in the sample. For devices intended for use inside triaxial cells, extensometers are manufactured with modules rotated 90°.
The standard model 3909 has a full scale measuring range of 0.5 mm. Measuring points are included with the extensometers, and additional adhesive fixtures are available.
Model 3909 extensometers are strain gauge devices, making them compatible with any electronics designed for strain gauge transducers.
Output, mV/V
2-4
Nonlinearity
≤ 0.20% depending on modification
Operating temperature range, ˚С
-40 to +100