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#1 |
Shock Therapist
Join Date: Sep 2016
City & State: Victorville, CA
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hardcore Geek
Posts: 570
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![]() What is it about scopes, that make them unique from multimeters? I ask that for two reasons based on my own experience with the last scope I had.
1) I learned that getting a scope to read current is apparently not a trivial thing and you need some fairly expensive probes to be able to do it. 2) When I tried to use the ground clip on the scope probe to read the signal over a single resistor by putting the ground lead on one side then the probe on the other side of the resistor, it immediately gave me some kind of a warning about over voltage I think ... I didn't leave the message up long enough I just saw the red and disconnected immediately... but I figured that the problem was that the ground lead has to be connected to a point on the circuit where there is no voltage at all and if you don't then it's all bad, but I don't understand why?
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#2 |
Great Sage 齊天大聖
Join Date: Dec 2009
City & State: Europe
My Country: some shithole run by Israeli agents
I'm a: Professional Tech
Posts: 24,396
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![]() the scope is grounded,
if what your testing is also grounded then you will get a voltage difference. a questionable trick is to forget the ground clips and put one probe on each side of the resistor. then use the math function to display A-B btw, always keep the probes on the x10 setting. to answer the first question, a meter just shows voltage or current. a scope shows it over time - like going from 2d to 3d ![]() |
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#3 | |
Shock Therapist
Join Date: Sep 2016
City & State: Victorville, CA
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hardcore Geek
Posts: 570
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![]() Quote:
Why is this trick "questionable"? is it somehow potentially unsafe? Right, but it seems that getting a scope to inject itself into a circuit as you can do with a multimeter .. is not something that scopes are really designed to do where as with a multimeter, you switch the hot lead over to the current port and then the meter is inserted into the circuit ... not something you can do - apparently - with a scope ... for some reason ... |
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#4 | ||
Super Moderator
Join Date: Jul 2005
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My Country: Sweden
Line Voltage: 230v 50Hz
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![]() Quote:
But there are still voltage ratings that must be respected in this case too. A good primer on this is the following EEVBlog video: EEVblog #279 - How NOT To Blow Up Your Oscilloscope! Quote:
The following video might give you an idea about the probes of a scope and what they really are: EEVblog #453 - Mysteries of x1 Oscilloscope Probes Revealed
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#5 |
Great Sage 齊天大聖
Join Date: Dec 2009
City & State: Europe
My Country: some shithole run by Israeli agents
I'm a: Professional Tech
Posts: 24,396
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![]() some usefull shit is here:
https://www.youtube.com/user/Keysigh...loscope/videos https://www.youtube.com/user/RigolTech/videos |
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#6 | |
Shock Therapist
Join Date: Sep 2016
City & State: Victorville, CA
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hardcore Geek
Posts: 570
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![]() Quote:
I normally love that guy's videos but he really drug this one out. ![]() |
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#7 | |
Shock Therapist
Join Date: Sep 2016
City & State: Victorville, CA
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hardcore Geek
Posts: 570
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![]() Quote:
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#8 | |
Great Sage 齊天大聖
Join Date: Dec 2009
City & State: Europe
My Country: some shithole run by Israeli agents
I'm a: Professional Tech
Posts: 24,396
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![]() Quote:
unless your using a laptop with no charger or other connection to a seperate mains powered device. laptop chargers capacitivly couple the output earth to the neutral input and ground - if it has one. |
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#9 |
Shock Therapist
Join Date: Sep 2016
City & State: Victorville, CA
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hardcore Geek
Posts: 570
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![]() OK, so if you were going to use a scope to look at the AC signal coming from an outlet, would you just leave the ground clip floating?
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#10 |
Great Sage 齊天大聖
Join Date: Dec 2009
City & State: Europe
My Country: some shithole run by Israeli agents
I'm a: Professional Tech
Posts: 24,396
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![]() yes,
the scope is already connected to mains ground. that's dangerous btw incase of a surge. if you want to monitor mains you can use an old transformer to drop the voltage and still see the waveform. infact to see how to use a scope on risky voltages - go watch some electroboom video's you can also watch AC current without an electrical connection by wraping the ground clip around a wire a couple of turns and then clipping it to the probe tip - to create and inductive coupling. Last edited by stj; 02-14-2021 at 05:52 PM.. |
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#11 |
Shock Therapist
Join Date: Sep 2016
City & State: Victorville, CA
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hardcore Geek
Posts: 570
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#12 |
Great Sage 齊天大聖
Join Date: Dec 2009
City & State: Europe
My Country: some shithole run by Israeli agents
I'm a: Professional Tech
Posts: 24,396
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![]() it works
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#13 | |
Super Moderator
Join Date: Jul 2005
City & State: ----
My Country: Sweden
Line Voltage: 230v 50Hz
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![]() Quote:
Both of these can otherwise make you come-a-gutsa ![]() |
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