Two differential probes - would you ever need more than one? - Page 1
Forum section: electronics / beginners

author: radiantcircuits
author_rank: Newbie
timestamp: June 05, 2020, 04:33:40 pm
content: I thought I got scammed buying a Micsig differential probe on AliExpress and hastily bought another one from ebay. Turns out the seller didn't scam me and long story short, I now have two separate differential probes (2x Micsig DP10013 kits).Is there any point having two?Was there ever a time you wished you had an extra differential probe?If you have two, are there any times you are glad you have the second one?The only thing I could find online where you would need an extra differential probe is when you're using three phase power, but I probably won't be getting my hands on a 3 phase transformer any time soon.I'm using the probes mostly for education and hobby use - if it turns out I don't need two, I'll sell the second one.

author: madires
author_rank: Super Contributor
timestamp: June 05, 2020, 04:48:25 pm
content: So you're looking for a reason to keep both? If you don't know how many you need, how should we know?

author: wizard69
author_rank: Super Contributor
timestamp: June 05, 2020, 06:30:11 pm
content: such probes can be very handy in motor control. You many not think you have a need at the moment but only you know where your interests will go. So there is no way to tell what your should do from our perspective.By the way the probes don't mean just motor control, anything that elevates a signal above ground that you need to use as a reference can benefit from such a probe.

author: artag
author_rank: Super Contributor
timestamp: June 05, 2020, 06:52:19 pm
content: A two-input scope is far more useful than a single-input scope.If the signals you happen to be looking at are best measured differentially there's every chance you'd need two and it's particularly nice to have two the same.Unless you can't afford to keep it, I'd say hang on to it.

author: Mr. Scram
author_rank: Super Contributor
timestamp: June 05, 2020, 07:16:29 pm
content: I've actually been looking for a good deal on a set of two. Having the ability to see two signals, especially something like input and output can be very useful. Just poking around a board can be a bit safer too.

author: schmitt trigger
author_rank: Super Contributor
timestamp: June 05, 2020, 07:34:46 pm
content: If you do three-phase work, definitively a pair of probes would allow you to monitor all three phases simultaneously in an open delta mode.

author: radiantcircuits
author_rank: Newbie
timestamp: June 06, 2020, 04:03:32 pm
content: Thankyou to everyone who replied, I might hang on to the second probe

author: Cubdriver
author_rank: Unknown
timestamp: June 07, 2020, 08:00:53 am
content: I've used two when looking at both rectifiers in a full wave center tapped power supply - their common cathodes are the positive output point, and their anodes are each connected to the opposite ends of the power transformer's center tapped winding, so everything is floating.Top trace is regulated power supply rail (filter cap was completely open); lower traces show the voltage across each of the two rectifiers - this gave quick confirmation both were good and that the filter cap was toast. The flat 'bottoms' are where the respective rectifier is conducting; the humps are the reverse voltage when they are not. When the rectifier output voltage fell as the transformer output switched polarity at the transition of each half cycle, the output voltage would fall out of regulation as seen in the top trace.A few minutes connecting the differential probes let me see everything in synch and confirm that the diodes were good and the filter cap bad.-Pat

author: IDEngineer
author_rank: Super Contributor
timestamp: June 07, 2020, 03:54:37 pm
content: I presently have a single diff probe, but have often considered buying a second because I do a lot of work with very isolated circuitry (read: where measurements like "isolation capacitance" are meaningful). If I want to measure two such signals simultaneously, I will need a second diff probe. So far I've been able to get by without a second one but it's been very tempting.Another reason is for different voltage ranges. My present diff probe maxes out at 65V differential at its inputs (it's specifically designed, and I specifically purchased it, for low level signals). If I wanted to safely measure a "high" voltage - the reason most people buy diff probes - I'd need a "traditional" diff probe with its x100/x500/etc. dividers and significantly higher input voltage tolerance.A third reason is redundancy. My low voltage diff probe is uncommon, I had to special order it from somewhere overseas (that I cannot remember right now) which involved a wire transfer and significant delay. If my one-and-only copy of that were to croak, I'd be shut down for quite a while. Sometimes it's worth the insurance policy to have a backup for critical tools like that. If your high voltage diff probe were that critical to your work, having a second one might be worth the investment.There's three reasons just off the top of my head.

author: gfmucci
author_rank: Regular Contributor
timestamp: June 09, 2020, 09:25:12 pm
content: The biggest "scam" about Ali Express is they charge your credit card the pico second you place the order, but they ship a few days to a week later and you get the item a month or two later. Most online retailers charge your card when the item ships.

author: IDEngineer
author_rank: Super Contributor
timestamp: June 09, 2020, 09:44:37 pm
content: Quote from: gfmucci on June 09, 2020, 09:25:12 pmTo be clear, I wasn't speaking of AliExpress and my diff probe didn't come from them. In my case, the overseas vendor wasn't even set up to accept credit cards (or maybe just not international cards?) and they required an actual wire transfer. I was kinda uncomfortable with that - we do wires all the time but usually to well-known companies and/or companies with whom we have a long standing relationship - but in this case it was going to someone we'd never heard of.Nevertheless, the transaction went perfectly and the item arrived in a timely manner. I'd have no hesitation ordering from them again.I just looked them up: Their name is Global Media Pro,www.globalmediapro.com. Another weird detail is they seem to specialize in cameras and other media equipment (hence the name), yet they carry a very specialized differential oscillosope probe. Who knows....