I need to make high voltage single-ended and differential measurements. Can I float the oscilloscope?
NO! “Floating the oscilloscope” means cutting the green wire safety ground pin on the power cord or using an isolation transformer to elevate the oscilloscope chassis above ground. There are several reasons for not floating the oscilloscope. The first and most important is safety. All external metal parts, such as the case and the BNC connectors, will be at the floating voltage potential. The second reason is ground integrity. Without proper chassis grounding, electromagnetic interference (EMI) protection is defeated. This can lead to many strange effects if there are even moderate levels of EMI present. The third problem is with probing. Floating the oscilloscope does not convert the probe ground reference lead into a valid probe input. The probe ground will have unpredictable impedance, including a variable capacitance to ground through the floating transformer. The fourth problem is with the floating transformer. The input power transformer is not immediately behind the AC input. Fi
