Which differential probe to buy - Page 1
Forum section: electronics / testgear

author: cybermaus
author_rank: Frequent Contributor
timestamp: December 18, 2023, 07:49:21 am
content: So, I am in the process convincing myself I should really get a differential scope probeI sometimes work on medium voltage stuff the normal 230/400 mains, but also Piezo drivers to 700VAnd I think I should really stop using the trick where I disconnect scope ground, and remember not to touch the BNC'sAnd also I often would like to match/trigger up high volt signal to a low volt signal.But, I am a hobbyist, a frugal one at that, with sometimes some sidegig work for the Piezo stuff, so I tell myself I should watch the budget.Long story short, out of this example list, which one should I get.Or maybe a more easily answered question, which one should I avoid.(not planning to buy at amazon, it is just a easily collected list)https://www.amazon.com/Differential-Probe/s?k=Differential+ProbeDesired features (I think they are pretty much standard features):- Safely measure up to 700V, so maybe a safety rating of at least 1000V- Possibility to also measure low volt, like 3.3V or 12Vwith reasonable detail, but avoiding common ground.- Mix and match those two, linking them as trigger.- Up to 100KHz PWM driven signals, so probably a 10MHz bandwidth is enough

author: Smokey
author_rank: Super Contributor
timestamp: December 18, 2023, 08:26:18 am
content: Dave sells one here:https://www.eevblog.com/product/hvp70/

author: ebastler
author_rank: Super Contributor
timestamp: December 18, 2023, 08:40:00 am
content: Quote from: cybermaus on December 18, 2023, 07:49:21 amThat's just a search query on Amazon, right? The results will look different for everyone, depending on which country they are in. If you have specific alternatives you are considering, it's better to provide the direct links to each product page.

author: cybermaus
author_rank: Frequent Contributor
timestamp: December 18, 2023, 09:15:18 am
content: Quote from: ebastler on December 18, 2023, 08:40:00 amGood point. Considering the Migsig MDP700 and DP10007 on shortlist, but really open to any suggestions, so a worldwide mix of Amazon selection may be OKhttps://www.eleshop.nl/micsig-mdp700-probe-6934.htmlhttps://www.eleshop.nl/micsig-dp10007-differential-probe.htmlBut I am worried, also do not understand, the max ratings of the "better" MDP700And I do not want to get the higher rather model, as they would be less useable on low voltage due to the higher attenuation.How can a 700Vpp be rated for max 600V to ground.Well, I guess I do understand how, but it does not make sense commercially. After all, most switching inverters are still connected to mains neutral and thus referenced to ground.Making this an unuseable 700Vpp range? Am I missing something?And the older, less physically nice, DP10007 does have 1000V absolute max, the specs are OK, but it seems a bit more bulky and messy with wires, especially the USB supply wire.

author: 2N3055
author_rank: Super Contributor
timestamp: December 18, 2023, 09:25:42 am
content: For playing with resonant piezo transducers, I would go with 1500-2000V rating... Just saying..

author: cybermaus
author_rank: Frequent Contributor
timestamp: December 18, 2023, 11:48:36 am
content: Quote from: 2N3055 on December 18, 2023, 09:25:42 amHmm, looking at some stored scope images, maybe you are right. Some of the HF switching noise do seem to get close to 1000VThat is, if I interpret the 1:100 self made voltage divider I have on it currently correctly.I probably should consider the HF noise for the absolute ratings, right?

author: alm
author_rank: Super Contributor
timestamp: December 18, 2023, 12:13:24 pm
content: For high frequency noise (depending on your defintion of high), you should also consider frequency de-rating: absolute max / CAT rating is usually only at DC / mains frequencies. Don't expect a 1000 V 100 MHz probe to survive 1000 V at 100 MHz. More like 10 V. There should be a voltage-frequency curve in the datasheet or manual. Though the low duty cycle may help the probe survive. There probably won't be any frequency de-rating up to a few hundred KHz.

author: cybermaus
author_rank: Frequent Contributor
timestamp: December 18, 2023, 12:34:09 pm
content: Practically, I am talking about this:(this has a 1:100 voltage divider, and measuring with normal DMM shows ~450Vac (rms) (if I recall correctly)

author: 2N3055
author_rank: Super Contributor
timestamp: December 18, 2023, 01:03:34 pm
content: Quote from: cybermaus on December 18, 2023, 11:48:36 amLike Alm says, you need to look at probe's derating curves.And also it is 700V when everything is OK. What happens if things go wrong, you catch some weird resonance and voltage shoots up ....These are lethal voltages and significant energies.. Be cautious.