After some research into motor startup current profiles, Fluke implemented the function called “INRUSH” as a more confident measurement of startup current. One of the more common causes of unpredictability is the fact that a number of approaches to measuring startup current are asynchronous to the event. That is, the measurement function may be in the middle of a measurement cycle when the motor starts and as a result looses significant information about the current draw profile. In order to avoid this pitfall the Fluke “inrush” function relies on first being “armed” by pushing the “inrush” button. The clamp meter is now set to wait for a triggering event before starting a measurement cycle. Upon seeing a triggering event, the unit takes a large number of samples during a 100-millisecond period and then digitally filters and processes the samples to calculate the actual starting current based on the current draw envelope. This results in a more accurate indication of the start current than previous clamp meter instruments.
MIN/MAX is a digital MIN/MAX and it is updated every time the display updates. Its sampling window opens and takes a number of readings and updates the Min or Max registers as appropriate. This type of Min/Max is most useful for longer term events such as those occurring on heavily loaded or long wire run circuits to record more regular voltage drops or load increases.