Oven-controlled temperature stability

Accurate measurements that are not affected by ambient temperature may be taken when the part or circuit being tested is placed in an oven whose inside temperature is held constant after a short warming-up period. This works very well, indeed, when the temperature inside the oven is held higher than the maximum ambient temperature. This is because the inside of the oven may be heated but cannot be cooled. This type of control is frequently used to stabilize a crystal oscillator or a surface acoustic wave (SAW) filter.