Safely using oscilloscope with CIE personal training lab

Thread Starter

Circuits123

Joined Dec 7, 2012
73
I've got a "personal training lab" from CIE (see picture middle of the page here: https://cie-wc.edu/Electronics-Technology.aspx). It has a function generator on it and I'd like to use it to learn how to use my oscilloscope. But I've read about the dangers of testing things while connected to A/C current. Does anyone know if/how I can safetly test circuits on this training lab with my scope? I don't have an isolation transformer.
 

tautech

Joined Oct 8, 2019
204
Most scope usage is simple while you remember the reference lead of a probe is at mains ground potential......the same as any metallic point on your scope. A DMM can help identify safe points to connect the probe reference lead to. One lead on mains ground and the other on where you wish to connect the reference to. Check in both AC and DC modes.

Therefore you can't connect the probe reference lead to just anywhere in a circuit and further all probes have a max voltage rating that further derates at higher frequency.
These 2 points will keep you safe and you should aim for complete safety first and foremost.

You don't mention what sort of scope you have but while all scope use is somewhat similar but use of CRO's vs DSO's is somewhat different however the most powerful feature of any scope is its triggering in which you aim for a rock solid stable waveform so mastering the trigger suite is something of the highest priority.
Good luck, stay safe and we've all been where you are at some stage.
 

Thread Starter

Circuits123

Joined Dec 7, 2012
73
Most scope usage is simple while you remember the reference lead of a probe is at mains ground potential......the same as any metallic point on your scope. A DMM can help identify safe points to connect the probe reference lead to. One lead on mains ground and the other on where you wish to connect the reference to. Check in both AC and DC modes.
So do you mean I can connect the probe's ground clip anywhere as long as I know it's a good ground?
 

tautech

Joined Oct 8, 2019
204
So do you mean I can connect the probe's ground clip anywhere as long as I know it's a good ground?
Know as in prove first !
It can be more complex than just a common ground with a scope however moving forward in little steps is the best place to start.

For some circuits their circuit ground may be isolated from mains ground and possibly at a different potential therefore when connecting a probe reference lead to this circuit ground this ground will be pulled to mains ground which may or not affect the circuits operation.
Connecting a probe reference lead to a point that isn't at mains ground potential can create a ground loop and in some circuits sparks and magic smoke will escape !
Measure, verify then connect.
 
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