Extensometers measure strain – the change in length of a specimen divided by the original length (gage length) of the specimen – by means of knife edges that contact the sample, one of which is fixed in position and the other located on a moveable arm.
On these models, the moveable arm is pivoted – the knife edge is at one end and the other end is attached to an armature that moves through an LVDT coil.
Most of these extensometers can be adapted to exact specimen holding needs by the options that are described below, but in their standard form they hold flat or round specimens from 1.6-16mm (1/16-5/8in).
Options & Accessories
- Averaging — With this type of extensometer, knife edges are placed on opposite sides of the specimen to provide an average amount of strain between the two gauge points.
- Film Clamps — These spring activated clamps allow precise strain measurement of thin materials up to 3mm/0.125in thick, including plastics and foils, without marring the specimen. This option is only available for non-averaging extensometers and typically requires the use of a counterbalance to support the extensometer.
- Breakaway Release — This option is ideal for measuring strain on samples with brittle characteristics that may cause premature failure. It typically requires the use of a counterbalance to support the extensometer and is available for both averaging and non-averaging type extensometers.
- Sheet Metal Attachment — This option allows the extensometer to accommodate thin, flat specimens. Note that this option is only available for non-averaging extensometers and typically requires the use of a counterbalance to support the extensometer.
Options & Accessories
- Extension Bracket — This option allows the extensometer to be used with samples that are thicker than maximum opening of 16mm/0.625in on the standard model. There are three versions where an extension bracket allows the extensometer to be mounted on samples that are 25mm/1in, 50mm/2in or 75mm/3in thick. This option is only available for non-averaging extensometers.
- Pneumatic Release — This option is combined with a swing-away support and allows the remote release of the extensometer from the sample.
- Counterbalance Support – This option is used to support the extensometer and is commonly used when the extensometer is attached to small or fragile samples.