摘要 |
<p>The method for measuring low pressure in a container uses pressure dependent gas friction. The friction is measured from the associated variation in the revolution rate of the rotor of a turbomolecular vacuum pump. Alternatively, the time for the rotor to run up to a desired rate of revolution is used as the measure of pressure, or the time taken for the revolution rate to decrease from one defined value to another. A further approach involves measuring the rate of change of revolution rate whilst constant power is applied. Similarly, the power required in order to maintain a constant rate of revolution may be used as a measure of pressure.</p> |