Measurements of pump properties

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Chapter 7

Summary Measurements of pump properties

The content of this short chapter Measurements of pump properties is aimed at providing some degree of understanding concerning the methods by which measurements of important pump properties – pumping speed and pump’s compression ratio – should be carried out, and gaining insight into the difficulties we can expect. Both the constant volume and constant pressure methods are dealt with. For measurement of the compression ratio of (ultra-)high vacuum pumps a special double test volume separated by an aperture is the commonly accepted standard. It is essential for all measurements to be discussed, that they are carried out under operating conditions, i.e. a while of time must elapse in order that switch-on effects (warming-up, initial degassing) have been passed and the vacuum system has become in an equilibrium situation.

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Contents Measurements of pump properties

7.1     Introduction 506
7.2     Measurement of ultimate pressure 506
7.3     Pumping speed measuring procedures 508
7.3.1  Constant volume method 508
7.3.2  Constant pressure method 511
7.4     Measurement of the pumping speed of a (ultra-)high vacuum pump 515
7.5     Measurement of the pump’s compression ratio 517

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