Electronics > Beginners
Oscilloscope for AC work ?
<< < (3/9) > >>
tautech:

--- Quote from: SND on May 03, 2019, 08:50:09 pm ---I look a bit more into the HV differential probes,  any brand/model in particular to consider?

--- End quote ---
Pintek DP-25 is a good entry level diff probe

Others:
Micsig
EEVblog
DDunfield:
Not running a bench scope without a ground is the right attitude, but unless you have a differential probe, it means that all of your measurements will be referenced to ground. You won't be looking across 3 phases properly, and even single-phase properly between neutral and hot.

You can make use of differential readings to use two channels as a single differential input with normal probes, but this is usually considered a MATH function, and doing so may prevent you from performing other match function which may include FFT on some scopes. Differential probe is a much better way.

Scopes with integrated power THD measurements are not common. I believe some of the Fluke MDA series I mentioned earlier do perform a THD measurement, but for the higher end models you are getting up $10k+  (at least in Canuck bucks). Would it be an option to use a device that can store waveforms and upload to a PC later for detailed analysis later?

Someone mentioned using 100x probe - good idea. If you decide to get away with 10x which *should* be ok for 120v circuits, DON'T use a 1x/10x switchable probe! - they WILL get switched and bad things will happen!
rstofer:

--- Quote from: SND on May 03, 2019, 08:50:09 pm ---I look a bit more into the HV differential probes,  any brand/model in particular to consider?

--- End quote ---
Our host makes one

https://www.eevblog.com/product/hvp70/

It is not in stock but maybe that is negotiable.  You can also use it as a frame of reference.

In industry, were we to make such measurements, we would need the full complement of Personal Protective Equipment (PPE) including flame retardant overalls, face shield, rated low voltage gloves and we would probably stand on an insulating mat.
bob91343:
For many purposes, one can simply put a decent quality transformer on the mains and look at the secondary with ordinary precautions.  Of course the transformer will distort the wave but it might not be serious, depending on what you are trying to do.

You could also try a couple of different transformers and see how the results compare.  But most power line transformers won't have a lot of response into the kHz region.

Another type of transformer that might be better is an output transformer from an old tube type hi-fi amplifier.  They usually can handle the voltage and are wound with more care.
bdunham7:

--- Quote from: Benta on May 03, 2019, 07:55:38 pm ---

I fully agree.
The only correct way of measuring mains on a 'scope is using high voltage differential probes. Everything else is a recipe for killing yourself.
Don't even think about battery 'scopes or isolation transformers.

--- End quote ---

First, make sure that your differential probe is specifically suited for the task (CAT III or IV rated in this case) and remember that they are not completely isolated and have non-trivial input loads in some cases.

Second, why do you dismiss battery operated scopes?  A proper one is as safe as a proper DMM, and if you showed up as an electrician to work in a panel with anything else you'd be thrown out. 
 
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod