Our laser extensometers can be used at elevated sample temperatures. Usually our so called 'parallel scanners' are chosen. With these types of laser extensometers two approaches are typically used in high temperature situations: Scattered Light and Shadowed Light

Scattered Light

The laser beam is sent from the scanner onto the sample surface. The scattered light is deflected by a mirror and detected by the receiver. This is close to the standard working principle of our laser extensometers.

Shadowed Light

The technique of 'shadowed light' shall be described for a compression test. (It is applicable to other tests like tensile test too.) In a compression test, the sample can be placed between two stamps. The laser beam is sent from the scanner through the furnace to the receiver. The beam is adjusted for that it is partly blocked by the stamps, but not blocked by the sample. With this setup, the distance between the stamps is measured - and therefore the length of the sample is determined.

Application Parameters

Laser extensometers are optical systems and are therefore sensitive to good optical conditions. When a system for high accuracy is used in a high temperature application, some data processing is required to remove the effect of turbulences. Evacuated tubes for guiding the scanning laser beam to the sample without turbulences can enhance the accuracy significantly.