This part of IEC 60947 applies to flow rate switches that sense the rate of flow of a gas, a liquid or a granular solid. These switches change their output state if a pre-set value for the speed of flow is exceeded. These flow rate switches are self-contained, have semiconductor switching element(s) and are intended to be connected to circuits, the rated voltage of which does not exceed 250 V 50 Hz/60 Hz a.c. or 300 V d.c. This standard does not specify the additional measures that are necessary for flow rate switches used in conjunction with explosive sensing materials and/or in an explosive location. This standard is not intended to cover devices with analogue outputs. The object of this standard is to state for flow rate switches: – definitions; – classifications; – characteristics; – product information; – normal service, mounting and transport conditions; – constructional and performance requirements; – tests to verify rated characteristics.