The determination of pressure in a high vacuum from the gaseous drag of a freely rotating sphere was already proposed in 1946 by Beams and co‐workers. On the basis of novel techniques, this method was developed from its original bulky and delicate experimental state to a practicable, compact instrument for widespread laboratory and industrial use. The present paper gives a detailed description of the gauge head functions, and of the method of evaluation of the rotor deceleration rate. The predictability of the gaseous drag is discussed in view of absolute pressure gauging. The feasibility of extending the measurement range up to atmospheric pressure is demonstrated on the basis of experimental results.

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