N00B Scope question(s) (Rigol DC1054Z)

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My scope was delivered on Monday. It's sure nice. Now what? ;-)

 

Actually, a couple more directed questions...

 

I watched the EEVBlog about not blowing up your scope (https://www.youtube.com/watch?v=xaELqAo4kkQ). And I admit it has me a little spooked (perfect time of year for that I suppose). Next I was reading the manual (http://beyondmeasure.rigoltech.com/acton/attachment/1579/f-0506/1/-/-/-/-/MSO1000Z%26DS1000Z_QuickGuide.pdf) where it says that the scope operates in Measurement Category 1. The definition of which is:

 

Measurement Category Definitions Measurement category I is for measurements performed on circuits not directly connected to MAINS. Examples are measurements on circuits not derived from MAINS, and specially protected (internal) MAINS derived circuits. In the latter case, transient stresses are variable; for that reason, the transient withstand capability of the equipment is made known to the user.

 

Question 1I am okay to use the scope on circuits powered by my bench PS's, right? Ultimately they do connect to MAINS (as I understand MAINS)...

 

My project involves using PWM to control an L293D circuit, pretty straight-forward stuff. Output on the L293D is roughly 0 - 15v. I have been searching around the forums and the Internet in general and it seems possible to inspect the various timers and my software configuration of said timers with the scope.

 

Question 2I should be able to observe the overflow registers on the AVR as well as the output voltage on the 293 to correlate the PWM signal and the output voltage; but should I worry about blowing up the scope?

 

The manual says the scope can take up to 300Vrms on the leads. I am still just super paranoid as it took months to save up for the scope.

 

Note: This is as much for experience with the scope as it is for troubleshooting my circuit.

 

Thanks for any and all feedback!

 

  • "Give me six hours to chop down a tree and I will spend the first four sharpening the axe."  -- Abraham Lincoln
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Relax.

 

Yes, you can use your scope to work on your circuit.

 

Attach the Ground lead to the Power supply's ground.

 

Use your other channels to probe your various signals.

 

Don't use it to debug your Main's connected TV, light dimmer, washing machine, or car ignition, without having first learned more about what is safe and how you can get into trouble.

 

JC 

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The thing to remember is that the scope is connected to mains earth and this continues down to the earth ring on the probe. If the earth of your probe touchee mains active , then sparks will fly and it might blow the shit of out the scope. I've done this many times, but the scope was a Tektronix and it tolerated such abuse, the probe was not so lucky.

In most of your circuits the available current is small, so a mistake will most likely have no bad effects.

Last Edited: Wed. Oct 5, 2016 - 09:59 PM
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Yep - the big danger is shorting something through the ground on the scope/probe.  You just have to keep in mind that the probe ground = scope ground = mains ground.  Don't connect it to anything that would short considerable current through that ground!

 

Most lab style DC power supplies are isolated.

 

Congrats on the new scope, the DS1054Z is a best bang for the buck for sure.

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I once went on a short course to Queen Mary College in London University (it was really just advertising to attract potential students).

 

The course involved a workshop with analogue/digital electronics.

 

I don't know to this day what it is I did wrong but I poked a scope probe at something on the bench.

 

There was quite a room shaking "bang" and that familiar whiff of burning electronics and I had managed to destroy a fairly expensive looking scope.

 

I was traumatised.

 

That was 36 years ago.

 

By trade I am a bit mangler.

 

I almost never get involved in the electronics side of things if I can help it.

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I did almost the same as clawson (hmm, now about 55 years ago, still in High School) except that, post-boom, the cause was obvious, right down to the melted probe ground lead. I had connected the probe to one side of the MAINS and was starting to attach the ground clip to the other side of MAINS. Then BOOM! That was probably the worst probe connection error I ever made, and never repeated. This was IN a company that makes oscilloscopes and which shall remain here un-named to protect the innocent. 

 

As far as using a scope with with a bench supply - relax. There are two ways you can connect your circuit to the power supply. One way is floating where none of the power supply terminals are grounded (to power line safety earth ground). Other way is with one or more of the supply terminals connected to ground. Generally, there will be little difference with either connection. A few circuits that MUST float might behave slightly differently when grounded (think EEG or EKG front ends, for example), but those are pretty rare cases. Some supplies have a ground jack on the front panel with a metal connecting strap that can be used to ground one of the active power jacks; THEN, you can tell if it is grounded or not. If you are concerned, unplug the supply and check for continuity between the round pin of the power plug (North American plug standard) and the various front panel jacks.

 

The place where you DO need to be concerned is with un-isolated off-line power supplies. Of course, those are even hazardous to human health, so there are more concerns than just the scope. 

 

By the way, this is pertinent to ANY oscilloscope.

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

Last Edited: Thu. Oct 6, 2016 - 07:33 PM