Measuring mainpower with a handheld scope and a differential probe

[Electronicstarter2024]

Good day,

I am new to the forum after having read many articles. It's great to see how so many people here share information and experiences with each other.

I have been searching for an answer to my question, but unfortunately, I have found several conflicting answers. Therefore, I would like to ask my question here.

I am using a handheld oscilloscope and want to measure the control signal, voltage, and frequency of a system. Since I want to measure higher voltages and the oscilloscope does not have fully isolated channels, I am wondering if a differential probe would be a good solution. However, I have read that a differential probe still requires a ground connection for safe measurements, while my handheld oscilloscope does not have a ground connection.

My question is: how can I safely measure the outputs of an HVAC compressor inverter using my Migsic MS210T oscilloscope? Does anyone have experience with this or can offer advice on the correct approach?

Thanks in advance,
Jeroen

[Electronicstarter2024]

"Good day, I have searched online for information about using a differential probe and a handheld oscilloscope without isolated channels. I’ve come across various opinions about the possibilities and risks involved. Does anyone have experience measuring 400V AC signals with an oscilloscope, specifically in combination with a handheld oscilloscope? According to the Migsic DP10013 manual, grounding is required, and the differential probe connects to the oscilloscope via USB. For safety and budget reasons, I am cautious about proceeding with this measurement. If anyone has tips, ideas, or suggestions, I would greatly appreciate hearing them. Additionally, if anyone knows where I can find more information on this topic, it would be highly appreciated."

[tggzzz]

An oscilloscope's principal purpose is to see the shape of the waveform.

You should read the scope manual to see the accuracy of the voltage measurements.

An inverter may not output a sinewave. If not, then you will have to determine how your load will react to a non-sinusoidal waveform.

I doubt a probe connects to a scope via USB.

There are several types of differential probe. You need an HV differential probe.

For information on probing in general and some safety information, see the references at https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

[FlexibleMammoth]

The reason many HV differential probes require earth ground is that they are not actually fully isolated, but have a very high internal resistance to ground, which may cause the BBC shell to float to dangerous voltages if not properly grounded.

Your scope has neither isolated BNC connectors nor isolation between the channels, which is more dangerous than a regular scope, since you can touch the exposed metal and be connected to the potential in the earth clip of the other Probe and there is no earth ground to protect you.

If you want to Connect this scope to a mains circuit, the earth lead must be at earth potential. If you use a HV differential Probe, it must be grounded to earth potential.

The only type of Probe that would be safe with this scope at a ground potential beyond safe voltages is a fully (e.g., optically) isolated Probe.