This Article is about how the Fluke-1770 Series Inrush Current capture feature works.
The setup is critical when using the Inrush Current Capture feature. The parameters you need to manage are which current probe you are using, what Range setting is selected and what Trigger level is set.
In the example below the running current is around 7A and the Inrush Current Trigger is set to 50A, and the expected Inrush Current is 550A. We are using the standard 1500A Flexi current probes that come with the Fluke-1770 Series. In the first test we used the Auto Range, the Auto Range will navigate between the 150A range and the 1500A range. In our test we are measuring around 7A, and the meter will use the 150A range because the running current is under 150A and if the level is greater than 150A, it will change and use the 1500A range.
The Fluke-1770 can use the Auto Range feature, or you can select the range that best supports the level of current you will be measuring.
The issue with using the Auto Range selection is it will change ranges automatically when the level is below 150A or above 150A when using the 1500A flexi current probes.
Below is the meter showing it captured and Inrush Current of 550A, but when you look at the results there is a gap for when the meter changes ranges.
Below are the details of the change, look at red box area and you can see the data gap when the auto range feature took place.
Below are the Waveform results with the missing data, the sinewave is chopped off at that top of the waveform giving us a clue the data got chopped off.
Below is an example with selecting the 1500A range instead of the Auto range choice.
Here is where the data will look different using the 15000A range instead of the Auto range.