Research gives crystal clear temperature readings from toughest environments

Researchers have developed a form of crystal that can deliver highly accurate temperature readings, down to individual milli-kelvins, over a very broad range of temperatures: -120to +680 degrees centigrade. The researchers used a "birefringent" crystal which splits light passing through it into two separate rays. Research has already shown that the size of the effect will increase or decrease in proportion to the temperature of the crystal. In theory therefore you could calibrate such crystals to be highly accurate temperature gauges. However, the use of birefringence in this way has significant problems in practice. This temperature measuring ability of highly birefringent crystals is badly compromised by changes in the thickness and orientation of the crystal. This adds expense to the manufacture and calibration of such crystals and makes them almost unusable in situations where, for example, vibration could alter the orientation of the crystal.