Noisy probe - Page 1
Forum section: electronics / beginners

author: Mike Fikes
author_rank: Contributor
timestamp: December 26, 2017, 04:53:32 pm
content: I recently got a Rigol DS1054Z, am new to oscilloscopes (have only had it for a few weeks), and suspect one of the probes might be bad. (The Rigol shipped with PVP2150 probes.)When measuring a slowly charging capacitor as it neared full charge, the trace would inexplicably "drop out" (showing a noisy reduced voltage around 90% of the actual voltage) but then return to tracing the exponential curve.In troubleshooting this by swapping out probes, using different channels,etc., I've isolated it to an apparent bad connection in the probe that I have been primarily using (associated with channel 1), with the noise being exacerbated if you handle the probe, and in particular, if you gently rotate the jacket between where the probe connects to the wire (see the attached picture).To further ensure that this has nothing to do with my capacitor breadboard setup, I was able to reproduce the issue by rotating the jacked when the probe is connected to the test compensation square wave on the scope. This doesn't happen with any of the other probes.Attached are pictures showing the noise when measuring the capacitor, showing no noise for the other probes (I rotated the jackets on all of them). Also shown is the noise when connected to the compensation test signal, along with a picture of the jacket I'm referring to.The questions I have are:Is this normal? In other words, did this probe just go bad because I was using it the most frequently?If not, is there some way I can disassemble the probe to fix the apparent bad connection? (It seems that with rotating the jacket, the noise has subsided somewhat, so I'm assuming there is just a bad connection in the probe.)I'm also wondering if these probes are just low quality, prone to going bad, and I should purchase a better set, or whether I just happened to be unlucky in getting a bad probe and I should follow up with the reseller.

author: cncjerry
author_rank: Unknown
timestamp: December 26, 2017, 05:43:49 pm
content: First, the probes are pretty bad. I broke a couple by pressing on the back while trying to clamp/unclamp from a post. the fine wire inside breaks.Second, you don't mess with the probe while taking a measurement.

author: Mike Fikes
author_rank: Contributor
timestamp: December 26, 2017, 05:48:08 pm
content: Thanks cncjerry. I should have clarified in the original description: The problem sporadically occurs even when not touching or otherwise handling the probe. It seems to occur more frequently in the capacitor test when the capacitor is nearing full charge.

author: jmelson
author_rank: Super Contributor
timestamp: December 26, 2017, 05:50:30 pm
content: I bought a new scope many years ago. The probes that came with it both failed within 2 weeks. I had some well-used Tek probes when I got them, that I've been using for, like, FORTY years. The hair-thin wire in one broke a year ago, and I was able to do some microsurgery to fix it. So, name-brand probes do seem to be a LOT more robust than the cheapies that come with budget scopes.Jon

author: Mike Fikes
author_rank: Contributor
timestamp: December 26, 2017, 06:04:10 pm
content: As a follow up: Here is a picture showing the "bad" probe and a good one, both measuring the same rising capacitor voltage, without touching anything, other than pressing the scope's print button at the end (where you can see the slight vibration seemed to cause an additional outage). In fact, it seems that just bumping the table or walking across the room causes probe outages.So, it sounds like, even if I were to get this one replaced, all of these probes might go bad in a short period of time because they are extremely poorly constructed. Since I'm so new to this, relying on others here to confirm that this is, in fact, par for the course. Maybe the truth is somewhere in between?

author: ataradov
author_rank: Super Contributor
timestamp: December 26, 2017, 06:58:24 pm
content: Quote from: Mike Fikes on December 26, 2017, 06:04:10 pmThis may be a one-off defect, or a user error. I have not heard complaints about Rigol probes, nor did I have any problems myself. I don't think I've ever had to discard a probe for electrical reasons in my life. They mostly fail mechanically - rubber parts get too brittle, plastic parts break, cable insulation gets damaged, etc.Probes are delicate things, so applying a lot of force, or tugging on them will lead to damage.

author: DimitriP
author_rank: Super Contributor
timestamp: December 26, 2017, 08:24:10 pm
content: Some probes "last" longer than others. Whether it's a game of chance, careful handling or the phase of the moon. I don't know.I have a set of four probes, bought at the same time and at least one of them has "BNC jack rotation disease".Since then I added a Probemaster that so far seems to not care if the BNC jack is rotated or looked at while measuring.

author: Mike Fikes
author_rank: Contributor
timestamp: December 27, 2017, 09:31:47 pm
content: It turns out the problematic probe would exhibit the issue when wiggling its witch hat. Interestingly when swapping witch hats with other probes, the problem stayed with the probe, and when removing the witch hat and connecting directly, no noise could be produced with the probe.Regardless, Rigol have decided to ship a replacement probe.

author: StillTrying
author_rank: Super Contributor
timestamp: December 28, 2017, 01:42:52 am
content: "Interestingly when swapping witch hats with other probes, the problem stayed with the probe,"As the problem seems to stay with the probe's point, it's probably worth a try cleaning the sides of the point. Stabbing the point into an eraser and rotating the eraser a few times should be safe enough to not remove any plating on the point.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: December 28, 2017, 02:22:30 am
content: Well, I had a DS5102CA (a series so ancient and unremarkable you can't even find it on Rigol's site anymore) and the included probes were also crap. One failed open at the 1x/10x switch.This is too bad, since it can send a beginner into a tailspin.