Noob question about my new oscilloscope

Delta Prime

Joined Nov 15, 2019
1,311
Hello again Mr. wayneh Sir. :)
Not following. Do you mean failing to connect the ground clip before probing?
I did not mean to open up a can of worms for you or confuse you in any way .Floating a ground-referenced oscilloscope is a dangerously lethal technique I use for “defeating” the oscilloscope’s protective grounding system by disconnecting signal common from the earth by either using an isolation transformer or mitigating the grounding system, which allows certain parts of the oscilloscope — namely the chassis, cabinet, and connectors — to cover the potential of the oscilloscope probe ground lead connection point.
Measurements taken using this technique are often inaccurate as a result of the total capacitance of the oscilloscope’s chassis being connected straight to the circuit one is testing at the point where the common lead connects.
:)
 

Jon Hoover

Joined Oct 10, 2019
34
Just something to remember, if you are measuring signals that are referenced to ground, you should be fine. You attach your ground clip to the signal ground and probe away. If you are measuring signals that are not referenced to ground, your passive probe may give you inaccurate results or may damage your circuit when you attach the ground clip to your circuit. I picked up one of the Micsig DP10013 inexpensive differential probes from Amazon for about $168. It saves me so much worry about possibly shorting my circuits with my passive probe. The cool thing about it is that it is USB powered and I just plug it into one of the USB ports on my scope and it's happy! The accuracy is fairly decent too.
 

Thread Starter

wayneh

Joined Sep 9, 2010
17,496
Yes, I've gotten the message to pretty much never use the ground clip. For most things I do, it just won't be needed. I guess battery powered devices are the exception.

Today I was wanting to use an old laptop brick as a 20V DC supply for a breadboard project. I didn't have the nerve to attach the ground clip on my o'scope to the "ground" output wire. It should be isolated, but ... just say no.

That particular brick was a POS it turned out. It output a simulated sine wave that measured 20V DC as expected but 43V AC with the leads in one polarity and zero in the other. Anyway the 43V fried my DRV8825 stepper driver in spectacular fashion - a tiny fire in addition to the magic smoke! Good thing I bought 5 at once.
 

MrChips

Joined Oct 2, 2009
30,708
As tautech says, I put the YELLOW cable markers on one probe to match the probe that is plugged into CHAN 1 and purple markers for CHAN 2 probe on both ends of the probe lead. You will find this useful.
 

Thread Starter

wayneh

Joined Sep 9, 2010
17,496
As tautech says, I put the YELLOW cable markers on one probe to match the probe that is plugged into CHAN 1 and purple markers for CHAN 2 probe on both ends of the probe lead. You will find this useful.
I have only yellow markers on both probes. Any idea where to find other colors?
 

Thread Starter

wayneh

Joined Sep 9, 2010
17,496
Did your scope not come with a packet of colored probe markers and other little goodies?
Mine is second hand, so no. Manual and two probes, that's it. I do have the spring-loaded clips. Is there a trick to keeping those attached more reliably? I've just been shoving the probe in the hole but it backs out pretty easily.
 

MrChips

Joined Oct 2, 2009
30,708
Mine is second hand, so no. Manual and two probes, that's it. I do have the spring-loaded clips. Is there a trick to keeping those attached more reliably? I've just been shoving the probe in the hole but it backs out pretty easily.
Do you mean the grounding alligator clip that is plugged into the side of the probe?

As mentioned in this and other threads you don't always need the ground clip since the scope is already grounded through the earth plug. You will need it when looking at high frequencies or when you see lots of ringing and reflections in the scope trace.

You can try bending the wires to get a tighter fit.
 

Thread Starter

wayneh

Joined Sep 9, 2010
17,496
Do you mean the grounding alligator clip that is plugged into the side of the probe?
I'm referring to the spring clip for grasping wires that you can slide over the end of the probe.

Another noob question: There's a plastic sleeve just above the probe tip, and it can be moved up and down a bit over a metallic section. I'm assuming that wider metallic barrel should not touch ... anything in the circuit. But does that plastic sleeve have some function I'm unaware of? I kind of wonder why it doesn't cover the barrel entirely.
 

MrChips

Joined Oct 2, 2009
30,708
Ok. I think I know what you mean.
Scope probes are expensive. I avoid using the probe without the outer plastic cover. You don't ever want to break the metal tip. Never insert the probe tip into the holes of a protoboard.

The first picture shows the exposed probe tip being used to get at fine SMD components.

scope probe1.jpg


This second photo shows how you would use the grounding spring to connect the ground to a ground plane.
I very rarely need to do this. This would be a special time with very high frequency signals when one would need to do this.

scope probe2.jpg
 

SamR

Joined Mar 19, 2019
5,031
I melted one of those on a hot component and had to buy a new probe because it jammed up the minigrabber to where it wouldn't work. Recently, I found replacements available on AliX, just the mini grabber part that goes onto the probe tip. Haven't come in as yet so can't say how good they are. I never use probes without it and do much the same with a jumper wire grabbed onto to poke into the breadboard.
 

Thread Starter

wayneh

Joined Sep 9, 2010
17,496
Ok. I think I know what you mean.
Scope probes are expensive. I avoid using the probe without the outer plastic cover. You don't ever want to break the metal tip. Never insert the probe tip into the holes of a protoboard.
Excellent point. I've been treating them much like multimeter leads. I need to change that.
This second photo shows how you would use the grounding spring to connect the ground to a ground plane.
I very rarely need to do this.
I can't imagine ever needing to do that, but good to know. I don't have the little spring.

Is there a trick to keeping the plastic cover on?
 

MrChips

Joined Oct 2, 2009
30,708
Excellent point. I've been treating them much like multimeter leads. I need to change that.
I can't imagine ever needing to do that, but good to know. I don't have the little spring.

Is there a trick to keeping the plastic cover on?
If the probe cover has been pulled on and off over the years it becomes loose and falls off. I wrap masking tape around the body of the probe to give the cover something to grip on to.
 

Thread Starter

wayneh

Joined Sep 9, 2010
17,496
If the probe cover has been pulled on and off over the years it becomes loose and falls off. I warp masking tape around the body of the probe to give the cover something to grip on to.
Mine is new. Is there a detent or something? What holds it on normally?
 

Thread Starter

wayneh

Joined Sep 9, 2010
17,496
To get the probe grabber/tophat/witches hat whatever you wish to call it to stay on the probe you need press it firmly until it clicks into its detent.
Well that clicked, literally! Nice.

For this 'scope, replacing the original probe (PP215) is "only" $35 and that includes the $10 kit with the colored rings, safety tip etc. So it could be worse.
 
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