The precision crystal heater provides temperature stabilisation for crystals. The circuit, which is built on AL2O3 ceramic substrate, has to be mounted on the 40 °C thermostat crystal. Then, the crystal is heated to 40.8 °C with a regulation accuracy of better than 0.1 °C. This provides high frequency stability.
The precision crystal heater is a in expensive alternative to completely heated oven oscillators (OCXOs). However, the stability values of an OCXO can not be reached.
Temperature stabilisation of crystals for high frequency stability