This article describes how to measure MOSFET drain voltage and current. As part of that discussion it outlines how to use several types of current probes, how to identify the correct measurement ...

Using A Fluke High Voltage Probe The Fluke 80K-40 HV probe For more precise measurements I use a Fluke 80K-40 high voltage probe.

Here’s how I do it using a Fluke high voltage probe as well as my own homemade probe. And what if you don’t have a probe? I have a solution for that too. How Long Is Your Spark?