[Solved] Choosing passive high voltage probe for oscilloscope (Newbie Question) - Page 1
Forum section: electronics / testgear

author: ballsystemlord
author_rank: Frequent Contributor
timestamp: August 09, 2022, 02:27:53 am
content: Hello,Intro:I'm new to oscilloscopes but not electronics. Please be gentle, I have a book on oscilloscopes for newbies from TI, but I'm a student so I need to plan my future so as to save/allocate money for future investments. Therefore, I'm asking here instead of reading through the whole book and hoping it answers my question. I have not searched online for the answer, as I'm not sure what terms to use or who's website produces quality information.I am aware that I should isolate either the oscilloscope or (preferably) the item being probed from the mains when testing. I have HV gloves rated at 12Kv spike and < 3000v working (For the unaware, those are the better type of common HV plastic-y gloves being sold online.) My oscilloscope is the MSO5074 (I wanted it for so long!Sadly, I still can't debug PCIe... ) It's limited to 70Mhz until I can hack it.Details (exhaustive):My current probes look like they're rated at only 25v at their full BW ( which I'd have to hack my scope to get as I couldn't afford the higher BW version.) I hope to work on projects, in the future, going up to 1Kv. Because of that and that my current probes (not that kind of current) are only rated at 25v at their full BW, I decided to save up for getting some HV probes.I have elected to go with passive probes to control the price I'd have to pay to get them and the fact that passive probes have almost nothing that will break on them (they may need calibrated less often too... I'll have to look that up some day soon.)Code:Highest V / V 1Mhz / 1Kv hz / Highest BW -- Pricing (rounded up)Mine:PVP2350300v 400Khz / 120v 1Mhz / NA / 30v 350Mhz -- $45High voltge probes:TX3125a 1.2Kv 700Khz / 1Kv 1Mhz / 1Kv 1Mhz / 225v 250Mhz -- $30TX3225a 2Kv 1Mhz / 2Kv 1Mhz / 1Kv 7Mhz / 325v 250Mhz -- $51CP3308R2Kv 2Mhz / 2Kv 2Mhz / 1Kv 4Mhz / 50v 300Mhz -- $77T3100 2Kv 1Mhz / 2Kv 1Mhz / 1Kv 7Mhz / 300v 100Mhz -- $15P4250 3Kv 30Khz / 175v 1Mhz / 1Kv 85Khz / 50v 250Mhz -- $15P2301C 5Kv 20Khz / 100v 1Mhz / 1Kv 12Khz / 12v 300Mhz -- $50HVP3000 9Kv 1Mhz / 9Kv 1Mhz / 1Kv 10Mhz / 1Kv 10Mhz -- $141 or moreP5100A 2.5Kv 2.8Mhz / 2.5Kv 2.8Mhz / 1Kv 18Mhz / 75v 500Mhz -- $280PR-55 7Kv 1Khz / 1Kv 1Mhz / 1Kv 1Mhz / 175v 50Mhz -- $284HVP-08 4Kv 1Khz / 500v 1Mhz / 1Kv 300Khz / 175v 40Mhz -- $190HVP-10R 10Kv 1Khz / 500v 1Mhz / 1Kv 100Khz / 100v 100Mhz -- $351HVP-18HF 18Kv 1Khz / 700v 1Mhz / 1Kv 400Khz / 150v 100Mhz -- $397HVP-39pro 39Kv 1Khz / 1.8Kv 1Mhz / 1Kv 3Mhz / 400v 50Mhz -- $533RP1018H 18Kv 3Mhz / 18Kv 3Mhz / 1Kv 50Mhz / 350v 150Mhz -- $604CT4024 4Kv 1Khz / 500v 1Mhz / 1Kv 275Khz / 175v 40Mhz -- $255CT4025 10Kv 10Khz / 5Kv 1Mhz / 1Kv 10Mhz / 250v 150Mhz -- $319CT4026 18Kv 10Khz / 9Kv 1Mhz / 1Kv 20Mhz / 300v 150Mhz -- $464CT4028 39Kv 10Khz / 12Kv 1Mhz / 1Kv 30Mhz / 300v 220Mhz -- $783PPE6KV-A 1.2Kv 3Mhz / 1.2Kv 3Mhz / 1Kv 7Mhz / 14v 400Mhz -- $850PPE20KV 20Kv 500Khz / 1Kv 100Mhz / 1Kv 100Mhz / 1Kv 100Mhz -- $2.1K: I think this is the same thing as the a3125 probes on ebay.: The derating curve only goes up to 100Mhz. I'm assuming it remains a flat line throughout the rest of the curve.: This is the derating curve for the whole series. I cannot imagine how this is a correct derating curve for the whole series, since they have voltage ratings from 5Kv to 20Kv. This probe series is a Texas instrument.: This is rated for 8Kv DC, but only has a derating curve starting at 4Kv (although the chart has it listed as 5Kv.) Also, although it has only 40Mhz BW, it's BW spec goes up to 100Mhz.: Oddly enough, the 120Mhz value is unavailable. Additionally, the slower probes also have entries for values through 100Mhz although they are rated for much lower BW.: Although it is rated for much less, these probes have derating values through 1Ghz! Why?: Probes have derating values through 100Mhz, but are rated for 50Mhz or 40Mhz.: The derating curve does not have any lines in it indicating if it's a linear or logarithmic chart. I'm assuming logarithmic as that's what the other probes are using in their derating charts.Question:I've collected information on HV oscilloscope probes. Some of them have really good specs, others get much better at higher frequencies. I'm uncertain if the specs are reflective of the instruments. Of course, if I bought a falsely advertised item, I might be able to get a return if I can prove it's defective or not as advertised. What would be a good passive HV probe for about 1Kv and a 350Mhz scope?Thanks!(Edited to make the table more clear and complete and fix some spelling/grammar mistakes.Added pricing to table.Added TX3225a probe to the table.Added HVP-08 probe to the table.Moved notes outside of the table for ease of reading.Added a whole bunch of probes, which are mostly out of my prince range.Added P2301C.Added HVP18HF. Moved all the pintech probes together.Confirmed the voltage of my PVP2350 probes that came with my oscilloscope.Added TVP-39pro.Updated values for the P5100A probe.)PS: I'll continue to update this if I get any new info. It's up-to-date as of April of 2023.

author: ballsystemlord
author_rank: Frequent Contributor
timestamp: August 09, 2022, 02:58:55 am
content: Probe documentation, for the curious.CP3308RHVP-10RT3200T3100P4060 P4100 P4250HVP-08P5100A datasheetP5100 manualP5100A derating curve.Texas probesRP1018HCT4024CT4025CT4026CT4028PPE6KV-APR-55PPE-20KV(Edited to fix URLs and change links to match probe names.Added a bunch of probes.Edited again to fix outdated tektronix spec for their P5100A probe.)

author: tautech
author_rank: Super Contributor
timestamp: August 09, 2022, 03:46:35 am
content: TBH you have little need for a lot of HV probes and CP3308R is our preferred 100x probe for just one reason ....... it's brightREDand serves as a continuous visual reminder why you got it out .....to work on HV that bites !How high need you really push voltages for scope use, truth is unless you're doing some very unusual shit, not very high at all and 100:1 probes are adequate for most everything.We carry a couple of 8KV 1000x probes but they are very slow sellers and from Pintek too, the HVP-08 that is reasonably priced.http://www.pintek.com.tw/productDetail/land-ctop-2/index/pscsn/17071/psn/127265Some time back I posted a pic with 1x, 10x, 100x and 1kx probes all connected to the probe compensation output on a SDS1104X-E, with a measurement showing each channel's correct 3V 1KHz signal.

author: ballsystemlord
author_rank: Frequent Contributor
timestamp: August 09, 2022, 04:13:05 am
content: Quote from: tautech on August 09, 2022, 03:46:35 amWhat I wanted to do, for now, is to be able to probe PC PSUs (I have a broken one that would make a nice lab power supply if I could fix it,) and later to work on making my own motor from scratch. I intended the motor to use higher voltages as I'd like to see how I can optimize the physical size of the motor vs. it's power output.

author: bdunham7
author_rank: Super Contributor
timestamp: August 09, 2022, 04:26:27 am
content: Quote from: ballsystemlord on August 09, 2022, 04:13:05 amI find the P2301C commonly found on eBay and Aliexpress to be quite adequate, well-made and useable. They do have a bit of voltage non-linearity, but you get what you pay for. You really aren't all that likely to have any frequency derating issues with those sorts of applications--you aren't too likely to see a 10MHz signal component at 300 volts or anything like that. I've used the P2301C on 2000Vrms@ 20kHz, that's 40MV-hz. If you're going to measure more than that, you need to think about it. Note that 240VAC or 400VDC with 5V ripple @ 1MHz or things like that are much, much less challenging.The CP3308R is a higher quality probe, although I don't like the configuration quite as much. YMMV.

author: tautech
author_rank: Super Contributor
timestamp: August 09, 2022, 04:51:47 am
content: Quote from: ballsystemlord on August 09, 2022, 04:13:05 amNothing too challenging then.A 100x probe or 2 should be enough for most tasks without throwing cash at 1000x probes when your money will be better invested in a differential probe or 2.Pintek's long proven DP-25 will suit most requirements but it depends on how deep your pockets are.http://www.pintek.com.tw/productDetail/land-ctop-2/index/pscsn/17072/psn/19265

author: ballsystemlord
author_rank: Frequent Contributor
timestamp: August 09, 2022, 05:13:20 am
content: I considered the P2301C probes, but I couldn't find a manual for them; or who manufactures them such that I could look the manual up.Do you know where I can see a manual or datasheet for those probes?

author: ballsystemlord
author_rank: Frequent Contributor
timestamp: August 10, 2022, 04:33:48 am
content: Quote from: bdunham7 on August 09, 2022, 04:26:27 amI managed to get a picture of the datasheet from an ebay seller. I could get a much better probe for the money if the manuals/datasheets are to be believed.

author: tautech
author_rank: Super Contributor
timestamp: August 10, 2022, 04:48:23 am
content: Quote from: ballsystemlord on August 10, 2022, 04:33:48 amThis style of probe is particularly for scopes with isolated inputs as both probe and its reference connection offer a high degree of insulation to CATIII levels and as such are never cheap.I can't now remember the EU company that makes them but they are used in Siglents SHS1000 series isolated input handheld scopes.https://siglentna.com/product/pb925-250-mhz-oscilloscope-probe/

author: LaurentR
author_rank: Frequent Contributor
timestamp: August 10, 2022, 06:14:05 am
content: Quote from: tautech on August 10, 2022, 04:48:23 amI believe these are Stäubli Isoprobe:https://www.staubli.com/br/en/electrical-connectors/products/t-m-products/high-frequency-measurement/touch-protected-passive-probes.htmlAlso used on the Fluke isolated scopes (190 series).

author: ballsystemlord
author_rank: Frequent Contributor
timestamp: August 29, 2022, 02:53:13 am
content: QuoteThat makes sense. (I took so long replying because I was reading up on what exactly isolated vs. non-isolated oscilloscopes are.)QuoteThey have almost no specs on the probes. Here's one that might be correct, though the color is different, it looks similar and the 100:1 value is correct.https://www.staubli.com/br/en/electrical-connectors/products/t-m-products/high-frequency-measurement/touch-protected-passive-probes/isoprobe-ii-100-1.html

author: ballsystemlord
author_rank: Frequent Contributor
timestamp: August 29, 2022, 02:54:21 am
content: QuoteThat particular probe is only 250Mhz, the P2301C is rated at 300Mhz according to it's manual.

author: ballsystemlord
author_rank: Frequent Contributor
timestamp: August 29, 2022, 02:55:54 am
content: In case anyone is wondering, I ended up going with the CP3308R. I think they'll work well for me.Thanks again!