MEASUREMENT OF POSITIVE DISPLACEMENT PUMP FLOW RIPPLE AND IMPEDANCE

The secondary source method forms the British Standard for pump fluid- borne noise testing. This is a powerful technique but requires care in order to produce accurate results. This paper describes practical asp ects for implementing the method. The requirements for the test rig, d ata acquisition system and analysis are detailed. The British Standard specifies that either mathematical modelling or linear interpolation is used on the source impedance measurements. A method for smoothing t he impedance results is described in this paper, which is shown to giv e more repeatable results than linear interpolation. Some physically r ealistic mathematical models of pump impedance are described, and thei r use in determining the internal flow ripple discussed.