This part of ISO 7278 gives guidance on the procedures and conditions of use to be observed if pulse interpolation is used in conjunction with a pipe or small volume prover and a turbine or displacement meter to improve the discrimination of proving. This part of ISO 7278 describes the three methods of pulse interpolation most commonly used and their conditions of use. It also describes the equipment and test procedures for checking that the pulse interpolation system is operating satisfactorily and it describes some methods of measuring the irregularity of pulse spacing for a meter.