Re: [CAD_CAM_EDM_DRO] Need help with O-scope

David G. LeVine wrote:

> At 10:06 AM 4/14/2007, you wrote:
>
>>I am having a problem with a mill set up with Gecko drives. There seems
>>to be a noise problem that has cropped up on the Z axis and I would like
>>to look at it with a scope. I have the use of a scope but have not used
>>one for several years and have forgotten a few things. The part I worry
>>about is; do I have to use an isolation transformer to keep from popping
>>an IC do to different ground potentials? The scope is a B K Precision
>>model 1570A with API 1X and 10X probes. Any help appreciated. Ed.
>
>
> Most 'scopes had isolation transformers built in. BK Precision
> SHOULD, but may not. It couldn't hurt.
>

No, this is not true. No oscilloscope is powered directly off
the mains, but that is not the same as an isolation transformer.
The frame of the scope, and the barrel of the BNC probe
connectors will be connected to the power plug ground pin.
Only on battery powered scopes will this not be the case.
If in doubt, use an Ohmmeter to measure from the BNC barrels to
the power plug ground pin, and you will have your answer.
Making a mistake with this could turn the entire scope into
scrap or get you seriously burned or shocked.

There are cases where you need to isolate the scope from ground,
such as to measure across the motor output terminals of a full
bridge driver. There are usually much better ways to make such
a measurement, for instance by making a differential measurement.

Jon