Oscilloscope probes - Page 1
Forum section: electronics / testgear

author: Howardlong
author_rank: Super Contributor
timestamp: January 03, 2015, 05:48:45 pm
content: FolksI recently bought some alleged 500MHz scope probes, but when I plugged them in they definitely weren't anywhere near that. As they looked similar to a couple of other probe types I have, I thought I'd see how they compared quantitatively.I did two tests on each probe.The first test was with a Jim Williams pulse generator with a 50cm coax pulse stretcher, terminated with a 50 ohm SMA 20dB pad, and the probing was done with the probe tip and ground spring directly on the SMA pad.The second test was with an HP 8656B RF signal generator, with the frequency adjusted for the 3dB point. The probing was done with the ground spring and probe tip directly on an inline 50 ohm BNC terminator at the end of a 6' 50 ohm patch cable.All probes were compensated on the same scope channel. The scope used is an Agilent 54831D (600MHz bandwidth).Pulse results50 ohm internal termination50 ohm external terminationAgilent 1165ATexas TX5230 - ~$20, purchased in Akihabara shop, same as this:http://hkaco.en.ec21.com/Texas_Passive_Oscilloscope_Probe--3475682_3476276.htmlBarsoom P6300 - ~$40,http://www.amazon.co.uk/gp/product/B00DRABRKM?psc=1&redirect=true&ref_=oh_aui_detailpage_o08_s00TP6100 - ~$15,http://www.amazon.co.uk/gp/product/B00GHIHW0K?psc=1&redirect=true&ref_=oh_aui_detailpage_o08_s01HQRP T5100 - ~$30,http://www.amazon.co.uk/gp/product/B005DQ2F1I?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00LIHUA P6500 - ~$30,http://www.tmart.co.uk/LIHUA-P6500-High-Sensitivity-Oscilloscope-Probe-500MHz-Gray_p284939.htmlAgilent 10073CMaplin HP-2060 - ~$20http://www.maplin.co.uk/p/60mhz-oscilloscope-probe-aq58nSo the biggest disappointment is the LIHUA P6500 that I originally suspected. It looks suspiciously identical to the TP6100 both physically and with regards performance: just look at the pulse profile. Physically, those two also look identical to the HQRP T5100 that performed really pretty well. I'll let others draw their own conclusions, noting that the Barsoom P6300, HQRP T5100 and Maplin HP-2060 all experienced resonance and therefore peaking to some degree between DC and the 3dB point.

author: tggzzz
author_rank: Super Contributor
timestamp: January 03, 2015, 06:14:54 pm
content: Nice article, which I've bookmarked and passed around to friends that might not realise howcrappysuboptimal probes can send you off on wild goose chases.

author: nctnico
author_rank: Super Contributor
timestamp: January 03, 2015, 06:42:15 pm
content: There is something off in the table. If I calculate the bandwidth based on the risetimes I get different bandwidths. For example the Agilent 1165A only has a bandwidth of 0.35/951ps=368MHz.Anyway, a much better rule of thumb is not to use a high impedance passive probe on frequencies over 100MHz because the capacitance screws things up badly. The bandwidth of such a probe is specified using a 25 Ohm source. Any other source (IOW a real life circuit) will give anything but the right results. Measuring high frequency signals calls for low-Z passive divider probes or active FET probes.

author: Howardlong
author_rank: Super Contributor
timestamp: January 03, 2015, 07:07:23 pm
content: I would take the risetimes calculated by the scope with a punch of salt, that is why I presented the screen shots too.The point of this was not tell everyone to go out and buy $1,000 fet probes, by the way!

author: nctnico
author_rank: Super Contributor
timestamp: January 03, 2015, 07:12:38 pm
content: If you do the math (loading a high frequency signal with 10pf) you realize you have to spend the cash or use a DIY solution:http://www.emcesd.com/1ghzprob.htm

author: Howardlong
author_rank: Super Contributor
timestamp: January 03, 2015, 07:17:28 pm
content: Yes, I have indeed already built two of those fet probes, and a resistive one as in your link, but thank you anyway.To be clear, the point of the test was to make folks aware of the trash probes that are around.The first test was done with a 50 ohm source, the second, if you read the description of my test,, presents 25 ohms.

author: Pjotr
author_rank: Frequent Contributor
timestamp: January 03, 2015, 09:55:50 pm
content: Quote from: Howardlong on January 03, 2015, 07:17:28 pmLuckily they do not cost you a fortuneGoing over 100MHz requires decent quality probes and preferable fixed 1:10 ones (not switch-able). These are never cheap but you do not need to dig up Tek money. Good high impedance HF probes have complex compensating networks with 2 or 3 adjustment points.

author: Howardlong
author_rank: Super Contributor
timestamp: January 03, 2015, 10:14:38 pm
content: Quote from: Pjotr on January 03, 2015, 09:55:50 pmI'd agree with that, the various Tek probes I have that are rated 400MHz and above (not in this test) have several adjustment points but some are covered up by a self adhesive label. However, the half dozen Agilent probes I have just have the standard compensation adjustment. They are all fixed 10:1 probes.The cheapo 300MHz Texas probes I have have readily available adjustment points. I got lucky on those, I happened to notice them in a store in Akihabara about six weeks ago, bought four, should've bought more, about $20 each, including ground springs and BNC probe adapters. Maybe time to go back again ;-)

author: Pjotr
author_rank: Frequent Contributor
timestamp: January 03, 2015, 10:55:57 pm
content: That's really a bargain if they perform as well as the $200 Tek probes. My point with the cheap probes, apart from electrical performance, is they fall apart after half a year of use.I myself use the 300MHz Testec TT-HF212 probes. Costing €45 here in Europe these are of reasonable quality and have a separate HF adjuster.

author: Howardlong
author_rank: Super Contributor
timestamp: January 03, 2015, 10:58:40 pm
content: Yeah, but I probably blew about $50 of roaming charges looking them up while I was in the store!

author: markce
author_rank: Regular Contributor
timestamp: January 04, 2015, 12:02:34 am
content: +1 for the 300MHz Testec TT-HF212 probes.3 adjustments, but nice pulse response. Fixed 1:10.Nice good handling and convincing build quality.

author: Howardlong
author_rank: Super Contributor
timestamp: January 04, 2015, 01:33:38 am
content: Quote from: Pjotr on January 03, 2015, 10:55:57 pmI think any probes will if not treated well: I have a good collection of Tek probes in various states of disassembly that I've accumulated over the years from various scope purchases. I guess because I work on my own stuff with my own equipment, I take care of them. All of the probes I have here that I've had from new are since I ever owned my first scope twenty or so years ago, all are perfectly functional, with all the accessories. I've had a couple of minor glitches, for example a ground clip getting mangled in a drawer and a dual lead coax adapter suffering a similar fate, but I either repair them myself or buy a replacement right away. As a matter of fact, both of those were Agilent probes, but they are the ones I use most.I can see why a scope that's in a university or used in a factory environment that's continually brought in and out of stores might suffer a worse fate though. If they ain't on your account, then less care is going to be taken, simple as that.

author: nctnico
author_rank: Super Contributor
timestamp: January 04, 2015, 11:09:44 am
content: In my experience probes start to suffer from bad contact between the ground clip and broken conductors inside the cable at some point. Even if you are careful with your probes the cable does get a lot of bending. When I suspect a probe is flaky it goes into the bin. Using a bad probe is a real nuisance.

author: macboy
author_rank: Super Contributor
timestamp: January 05, 2015, 02:32:48 pm
content: It is my experience that all probes need proper high frequency compensation to be performed in order to match them to the particular scope. With a random probe+scope combination, you can expect neither flat frequency response, nor flat pulse response.

author: Pjotr
author_rank: Frequent Contributor
timestamp: January 05, 2015, 02:49:19 pm
content: That is only true for a limited range of scopes/probes. Probes are specified over a range of input capacitance, usually 10pf - 30pf and some up tot 50 pF. If your scope input capacitance is within that range there is no problem with interchangeability. Problem can be sometimes dedicated signalling pins around the scope's input BNC.

author: macboy
author_rank: Super Contributor
timestamp: January 05, 2015, 03:28:42 pm
content: Quote from: Pjotr on January 05, 2015, 02:49:19 pmWithin that range, you will be able to adjust the LF compensation properly, but this does not account for high freqency effects. All scope inputs have different parasitics, and the high frequency compensation adjustments on good HF probes are there to adjust the response of the scope+probe combination.On my cheaper probes (Velleman probe250) these adjustments are easily accessible through holes on the compensation box at the BNC connector. On my Tek probes, I usually need to physically dismantle the compensation box to access these trimmers. Some images I found to illustrate:The basic idea is to feed a fast, flat top pulse (500 ps or faster for 500 MHz scope/probes systems) into the probe and adjust the trimmers for fast rise and minimal overshoot. This adjustment is not the same as the LF compensation that everyone is accustomed to. But just like the LF compensation, a probe that is tweaked perfectly for one scope will be off when plugged into another one. Sometimes the difference between two channels on the same scope is enough to warrant having separate probes tweaked specifically for each channel. Manuals for passive probes from Tek, HP/Agilent/Keysight, Lecroy, etc., all describe these adjustments.

author: Pjotr
author_rank: Frequent Contributor
timestamp: January 05, 2015, 04:04:54 pm
content: Oh, in that way. Looks standard practice to me to adjust your probes to the particular scope used with it. Or even the channel on that scope. When you wrote "a random probe+scope combination", I did read probes and scopes of different brands.

author: Dexter2
author_rank: Contributor
timestamp: May 20, 2019, 07:51:16 pm
content: Howardlong made an excellent post. A shame I did not see it sooner. I needed some cheap probes and bought the P6500 Chinese probes. Build quality is quite good as they are a copy from the Tektronix 6139B probes, but performance it terrible. Practically the probe has the -3db point below 20Mhz so it represents a square wave signal nicely only to a few 10Khz.Image of the P6500 Probe:I measured the frequency response of the probe and this is the result. While it is possible to resolve signals up to 500Mhz the frequencies over 20Mhz are attenuated heavily (compared to quality 500Mhz pasive Tektronix probes). No wonder Tek probes cost so much, even used ones... Freqency response was measured using a IFR 2025 2.5Ghz signal generator set to +13db and a MDO3054 scope (Y-axis are Vrms values)."Perfect" 10Mhz signal measured:Compared to Tektronix TPP0500:Just a reminder to anyone not to make the same mistake as i did.

author: jjoonathan
author_rank: Frequent Contributor
timestamp: May 20, 2019, 10:10:03 pm
content: Are you sure about your setup? I get different results.If you are sure about your setup, we might be dealing with bad clones of good clones. Lol.

author: Kosmic
author_rank: Super Contributor
timestamp: May 21, 2019, 01:01:15 am
content: Did the same test with mine (P6500 probe) but with a noise source from DC to 500Mhz. The noise source was 50Ohms terminated and the probe was connected with a probe adapter to the bnc connector.DC to 500Mhz, 50Mhz per division. In white, the noise source and in green, the frequency response of the probe (P6500).Look like it start dropping at around 450Mhz.Also tested the rise time with the calibration output of my lecroy oscilloscope. <= 1ns Rise, 25ns Width, 1V amplitude.I had to adjust compensation to get those results though. It's really not obvious but 4 trimmers are hidden in the plastic shell of the base of the probe.

author: bitseeker
author_rank: Super Contributor
timestamp: May 21, 2019, 02:16:46 am
content: Looks good. Maybe therearebad clones of good P6500 clones.

author: jjoonathan
author_rank: Frequent Contributor
timestamp: May 21, 2019, 03:00:37 am
content: I think I accidentally solved the mystery: the probe -> BNC adapter is very easy to partially unseat, even after seating it as well as I can. A tiny bump is enough and the partially unseated state isn't visually obvious.Video:https://photos.app.goo.gl/H3d7Kci8NdBfjQW18

author: jjoonathan
author_rank: Frequent Contributor
timestamp: May 21, 2019, 03:20:20 am
content: Here's a PMK 500MHz probe for comparison. The differences in risetime and loading are unremarkable, but the PMK BNC adapter is very difficult to unseat in a visually non-obvious way, even when I actually try.Video:https://photos.app.goo.gl/avtGw9bkPqDUBUNw9

author: bitseeker
author_rank: Super Contributor
timestamp: May 21, 2019, 03:23:27 am
content: Good catch.

author: jonpaul
author_rank: Super Contributor
timestamp: May 21, 2019, 11:01:31 am
content: Hi there, I am a retired EE, have been collecting, studying and using probes since 1970s, including FET, differential, current and high voltage probes.I think that TEK probes are far superior to HP, Lecroy, etc. The Yokogawa are a close second.The cheap Chinese knockoffs are a waste of time and money!Most abberations can be traced to a long ground return path. Bayonet and Micro coax adaptateurs help that issue.For Best BW and pulse response on 50 ohm scopes and plug-ins, use a Zo probe. Very low capacitance 1...1.5 pF and 500 ohm résistance in a 10X. BW on Zo probes can be 1-6 GHz!We use tek P6156, but be careful in buying off ebay as they must be complet and are easy to damage!https://cal.equipment/doc/Tektronix/TEK%20P6156%20Instruction.pdfThe active probes FET are of limited use as they need power, are easy to damage and bulky.For everyday use on 400 MHz scopes and 1 Mohm input, eg 2467B, we use the TEK recommended P6137, 10x.https://download.tek.com/manual/070643203.pdfI humbly suggest to new probers, see the Tek concept book series of 1980sOscilloscope Probe Circuits, a really excellent overview.https://www.davmar.org/TE/TekConcepts/TekProbeCircuits.pdfFinally, Here's a modern Tek note on probeshttps://download.tek.com/document/60W_14232_9_MR_Letter.pdfHappy Probing!Bon journéeJon (in Paris)

author: Kosmic
author_rank: Super Contributor
timestamp: May 21, 2019, 01:51:34 pm
content: Quote from: jonpaul on May 21, 2019, 11:01:31 amInteresting read. Thank you for the link.

author: jjoonathan
author_rank: Frequent Contributor
timestamp: May 21, 2019, 06:27:25 pm
content: Thanks for the links and the overview! It's not far off of the "overview from 10,000 feet" that I got years ago and that has served me well. There's more to say, but it is out of scope for this thread.However, I think it does all of us a disservice to pretend that the value market doesn't exist. In a professional environment, dropping a few hundred (or a few thousand, or more) dollars on a probe makes sense. Predictability and convenience have a gigantic premium when you're paying a half dozen engineer wages and racing to market. Well-to-do or semi-professional hobbyists such as you and I might also reasonably choose to pay a premium for reliability and convenience. But it is important to respect those who must make do with less. This thread is about helping them, and in this day and age the value options are good enough to deserve their attention.Case in point: the P6500 we have been talking about. It's a $30 clone of a $500 new / $150 used Tektronix probe. It does the same job as the brand name probe to within a tiny sliver of the performance margin. One of its accessories is unreliable -- but I don't think that accessory is even included with the Tek probe, so you can throw it in the trash bin without upsetting the value calculation. Or hold onto it and remember the caveat. Even if reliability is the concern -- and for a hobbyist, unlike a professional, it might reasonably not be -- the $120 in savings could likely be better invested elsewhere, e.g. in replacing cheap BNC bias tees, which in contrast to the P6500 do a good job of earning the contempt directed at them.Your caveat about frequency ranges is right on point, though. 10pf of capacitance hits 50 Ohm at 300MHz. Regardless of the brand or lack thereof, it really isn't much of a high impedance probe at that frequency anymore!

author: jonpaul
author_rank: Super Contributor
timestamp: May 23, 2019, 04:51:50 am
content: Hello againOver the years I Have paid $20...60 for excellent condition Zo and 1 meg 10x Tek probes like the ones I have mentioned.It takes patience and persistence but you can find bargains on epay.In my experience its penny wise and pound foolish to buy the cheap Chinese knockoffs.Just an old timers thoughts!Happy ProbingJon

author: Dexter2
author_rank: Contributor
timestamp: May 26, 2019, 08:15:32 am
content: Yes, the setup was ok, as you can see the Tektronix probes measure as expected in comparison on the same setup.My purchased P6500 probe also looks a bit different from what I see from Kosmic pictures. It has a black cable that is also a bit thinner. So, the argument is true, mine are a different knockoff.I don’t know if there are any additional internal pots for compensation, but I don't want to disassemble it as I want to return it to the seller as they are obviously garbage.

author: Dexter2
author_rank: Contributor
timestamp: May 26, 2019, 08:24:44 am
content: I completely agree with you jonpaul. The only time I broken this rule I got kicked in the but with 500Mhz probes that can be used for nothing.In comparison to expensive but probably the best passive probes from Tektronix I also have good experience with new German probes from TESTEC. They never let me down and only little more expensive than the Chinese probes. the only think i don't like about them as they are a bit bullky like lower priced segment Keysight/R&S pasive probes. But that depends on taste...

author: Dexter2
author_rank: Contributor
timestamp: May 26, 2019, 09:15:06 am
content: Another thing. I just measured the capacitance of my P6500 probes and its 14.2pF (advertized as 12pF). So even from this perspective it does not live up to the marketing.

author: jonpaul
author_rank: Super Contributor
timestamp: May 26, 2019, 01:20:04 pm
content: Be cautious in measuring small capacitances, like probes!You need a high measuring frequency, even 10 KHz is not enough for good accuracy.Stray capacity to ground is an issue.We use HP and Wayne Kerr bridges at 100kHz-10 MHz and have shields and guards.A network analyzer is another method.The handheld digital C meters will not give better than a few pF accuracyEnjoyJon

author: Kosmic
author_rank: Super Contributor
timestamp: May 26, 2019, 03:11:29 pm
content: I took the time to run some tests on different probes, and it confirm what Jon is saying.Part1:https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg2416473/#msg2416473Part2:https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg2436075/#msg2436075Tektronix probes are performing a lot better than every Chinese probes I tested.

author: Dexter2
author_rank: Contributor
timestamp: May 26, 2019, 06:23:02 pm
content: Quote from: jonpaul on May 26, 2019, 01:20:04 pmHi jonpaul,I measured with 100Khz on an new Japanise NF ZM2372 with 5V drive voltage and proper open/short compensated probes. Tektronix TPP0500 measured as 4pF (<4pF Specified), P6139B as 8.2pF (8pF specified) so i'm quite confident in the measurement of my P6500 as 14.2pF.

author: jonpaul
author_rank: Super Contributor
timestamp: May 27, 2019, 12:30:26 pm
content: Hello allVery Odd to see probes with more than one compensation adjust.The Tek 10x probes have a single trim capacitor.Only current and high voltage probes need more than one..Has anyone ever opened the Chinese or other probe with 2 or more compensation adjustment?Post a schematic?Just an interesting question.CheersJon

author: Dexter2
author_rank: Contributor
timestamp: May 27, 2019, 03:55:50 pm
content: Hi everyone,Today I received instructions with pictures from the seller of the P6500 probes how to optimize them. I think the thought was, if I’m not satisfied, I can still return them after the procedure. Disassembly was quite simple, and I must say mine also looks the same inside as the pictures of Kosmic even if the cable is black and thinner. There are two trimm capacitors and 3 potentiometers. The same construction as within the Tektronix P6139B probe.After about half an hour playing with the settings the probe performs much better. -3db point is at 100Mhz so still no 500Mhz passive probe but better (-6db is actually near 400Mhz…). My performance is no in the range what Kosmic and jjoonathan measured.Below the old vs new frequency response vs the P6139B probe:35ps rise time Square wave 10Mhz signal "P6500 received settings" (Yellow is reference)35ps rise time Square wave 10Mhz signal "P6500 Optimized settings" (Yellow is reference)35ps rise time Square wave 10Mhz signal "P6500 Optimized settings zoom" (Yellow is reference)Optimization setup:Manufacturer optimisation procedure:Addjust the trimmers in the order of R1->R3->R2 then repeat to obtain optimal response. It helps also to tweek the hi freqency response if you tweek C4.To sum things up, clones seem to be the same as others on the forum have, it just seems i got a lot with bad internal adjustment. The probes if adjusted can resolve frequencies over 100Mhz and i can not describe them as terrible anymore. Still the usefulness with their high capacitance is limited. Even with an 50ohm source the probe loading is considerable influence over 100Mhz. So in general i would say a 100Mhz probe with extended response:) Its one thing to measure signal generator outputs or pulse generators and another a real circuit.But then if i compare this to a low cost TPP0250 (250Mhz) Tektronix probe that can be had for 30-50€ if you are patient on eBay and their 3.9pF capacitance this is no comparison. But its a shame the TPP range can be only used on modern Tektronix scopes and the P6139B is their last higher freqency universal one... I will also do a comparison to German TESTEC HF212 300Mhz probes when i get them. They can be had for 44€ new.

author: worsthorse
author_rank: Super Contributor
timestamp: May 27, 2019, 07:09:02 pm
content: Quote from: jonpaul on May 21, 2019, 11:01:31 amJon, thanks for this!Second this... track down the Tektronix concept series notes on oscilloscope and probe circuits. The material is still relevant and will teach you a lot about how oscilloscopes and probes work and interact with circuits!EDIT: and if you are going to buy one good set of probes, used P6137 price/performance is pretty darn good.

author: Kosmic
author_rank: Super Contributor
timestamp: May 27, 2019, 08:55:55 pm
content: Quote from: jonpaul on May 27, 2019, 12:30:26 pmTektronix has a lot of probes where the high frequency adjustment are hidden in the base of the probe. Same as the P6500. But in the manual they normally explain how to do that. In the case of the P6500 it's really not clear that you can open the plastic case.Ex, high frequency adjustment of the P6134:Ex, high frequency adjustment of the P6106:

author: jonpaul
author_rank: Super Contributor
timestamp: May 27, 2019, 09:04:51 pm
content: Hello all,Many Thanks for the probe adjustment notes!I never used the internal tweaks, the single exposed trim always worked fine for me.Certainly Tek P6137 is one of the best 10x, recommended for Tek 2465/7 series.Be sure to use the shortest ground clip if pulse or wideband is important.Happy Probing!Jon(from Paris)

author: tautech
author_rank: Super Contributor
timestamp: May 27, 2019, 09:09:18 pm
content: The new SP3050A 500 MHz passive probe for the SDS5000X models has 2 HF adjustments in the BNC termination.https://siglentna-qwavztc8hvq2w.stackpathdns.com/wp-content/uploads/2019/02/SP3025A_3050A_Users_Guide.pdf

author: Dexter2
author_rank: Contributor
timestamp: May 28, 2019, 05:52:17 pm
content: Quote from: jonpaul on May 27, 2019, 12:30:26 pmOn jon's request the schematic of P6500 compensation. Maybe someone else also finds it interesting...

author: exe
author_rank: Unknown
timestamp: May 28, 2019, 09:52:34 pm
content: Quote from: Dexter2 on May 27, 2019, 03:55:50 pmWhat's the source impedance?

author: Dexter2
author_rank: Contributor
timestamp: May 29, 2019, 05:54:16 pm
content: Source impedance is 50ohm (but the signal generator has an ALC level circuit to hold the level). Probes ware connected directly to generator output via direct adapter(no cables) to measure the frequency response.

author: starlight_tools
author_rank: Contributor
timestamp: May 30, 2019, 11:09:26 pm
content: Looking to get a set of 4 pcs 100X probes for the SDS1104X-E scope that I have ordered.I have narrowed the selection down toP4250Pintek CP-3308RB&K PR2000BAny thoughts on these?

author: tautech
author_rank: Super Contributor
timestamp: May 31, 2019, 12:08:29 am
content: Quote from: starlight_tools on May 30, 2019, 11:09:26 pmThe Pinteks are what I've got for stock of 100x probes when I order stuff from them. They're well priced and well enough spec'ed for when you need them.http://www.pintek.com.tw/files/pintek/CP-3308R-spec.pdfP4250 OTOH has only a 10M tip impedance according to the manufacturers website and that alone would put me off them.BK one looks like the Pintek.However when working with HV when you want these probes it's good to have a bright red one to remind you you're playing with stuff that bites !Take care and stay safe.

author: starlight_tools
author_rank: Contributor
timestamp: May 31, 2019, 03:47:44 pm
content: Thanks gang,Pintek CP-3308R it is, got a confirmation this morning that they have been shipped from Taiwan, estimated delivery of June 6 to the 13th.https://www.ebay.ca/itm/2pc-Oscilloscope-Probe-Kit-CP-3308R-100-1-300Mhz-1500V-100M%CE%A9-Readout-Pin-PINTEK/142102785647Now for the ISFEs, no rush on those as I have to replenish my mad money fund.On another note, ordered a few sets of DMM leads, 24-in-1 Silicone Cat III 1000V. I have been looking at the silicone leads due to their high temperature characteristics to connect a DT33C DMM with Temperature measurement to a 1300 deg C K type probe for heat treating metal.https://www.ebay.ca/itm/232864780778Walter, TTDr

author: worsthorse
author_rank: Super Contributor
timestamp: May 31, 2019, 06:02:19 pm
content: Quote from: tautech on May 31, 2019, 12:08:29 amTautech, are the Pintek probes only available through ebay? Can't seem to find a US distributor...

author: tautech
author_rank: Super Contributor
timestamp: May 31, 2019, 08:32:00 pm
content: Dunno wch, surely there's someone over there that can get them.Google fu should find a supplier.

author: starlight_tools
author_rank: Contributor
timestamp: May 31, 2019, 10:34:10 pm
content: Found another supplier for Pintek, the price was better than the supplier that listed them on ebay, Globalmedia.com, but they are located in Auckland NZ and payment terms were wire transfer or local bank transfer.Walter

author: worsthorse
author_rank: Super Contributor
timestamp: June 01, 2019, 03:11:59 am
content: Thanks all. Looks like getting them shipped from TW (and ebay) is my only option.

author: starlight_tools
author_rank: Contributor
timestamp: June 06, 2019, 02:04:50 am
content: Quote from: starlight_tools on May 31, 2019, 03:47:44 pmProbes arrived on the 4th, still waiting for the 'silly scope.Be careful looking at the "see other items" cart filled up fast with all sorts of other stuff.

author: starlight_tools
author_rank: Contributor
timestamp: June 12, 2019, 05:16:14 am
content: Oscilloscope arrived in and I calibrated the CP-3308R probes and the stock PP510 probes.Noticed that with the CP-3308R probes, one did not have the red insulator over the adjusting screw, but had the metal screw showing, and that the adjusting screw driver did not fit as well as it did with the probes with the red plastic "screw caps". the supplier stated, when asked that this was the new design.Hope this does not present a problem later on.

author: Finderbinder
author_rank: Regular Contributor
timestamp: December 19, 2020, 08:01:23 pm
content: May someone explain how to check probe's BW properly don't having expensive gear?

author: tggzzz
author_rank: Super Contributor
timestamp: December 19, 2020, 09:27:59 pm
content: Quote from: Finderbinder on December 19, 2020, 08:01:23 pmWhat matters is the scope, the type of probe, the probe's compensation, the way the probe is attached to the circuit, and the circuit. Concentrating on the probe alone is an academic exerciseOf those, the key points people tend not to consider are choosing the appropriate type of probe, and the probing technique.

author: exe
author_rank: Unknown
timestamp: December 19, 2020, 10:56:24 pm
content: Quote from: Finderbinder on December 19, 2020, 08:01:23 pmI connected probes to siggen and measured amplitude of sine wave. To be sure it's not just peaking at a particular frequency I did test over multiple frequencies. Turned out that cheap probes (afaik pp-150) were noticeably better (in terms of amplitude) than the bundled once. I don't remember if siggen output was terminated with 50 or not, but it probably should. Also, ground lead should be eliminated for such measurements.One may probably use a pulse gen or something. But I'm not sure how to make a correct setup and how to evaluate results.

author: nctnico
author_rank: Super Contributor
timestamp: December 20, 2020, 12:06:30 am
content: Quote from: exe on December 19, 2020, 10:56:24 pmProbes are specified with a signal source impedance of 25 Ohms.

author: tggzzz
author_rank: Super Contributor
timestamp: December 20, 2020, 08:53:38 am
content: Quote from: exe on December 19, 2020, 10:56:24 pmIn a practical sense that is easy. In a theoretical sense it is more tricky.A scope shows the time-domain shape of the waveform, so if you know (by independent means) the waveform shape, you can compare it with what is displayed on the screen. The simplest such waveform is a rectangular wave with flat top/bottom and a risetime that is faster than the scope+probe combination.You are unlikely to get that from a general purpose sine/square/triangle waveform generator, since the risetime is unlikely to be fast enough and there may be ringing.Your best bet is either Leo Bodnar's generator, or you can make one as shown here:https://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg1902941/#msg1902941The above practical test is especially useful in that you will be able to see the effect of your probing technique, which will dominate that a properly adjusted probe.Probe manufacturers are interested in avoiding the problems with probing technique, so they have adaptors that connect a signal generator directly to a probe tip, with other specified conditions. Such theoretical tests are of little value when making real-world measurements.One example of poor and improved probing technique (plus theory) is found here:https://entertaininghacks.wordpress.com/2015/04/23/scope-probe-accessory-improves-signal-fidelity/https://entertaininghacks.wordpress.com/2016/09/17/scope-probe-accessory-higher-frequency-results/

author: jonpaul
author_rank: Super Contributor
timestamp: December 20, 2020, 10:43:42 am
content: Rebonjour a tous: Fine to see so much activity on this old topic.Glad my notes were useful to some. A few comments:1/ Testing and CAL of probes: Highly recommend Leo Bodnar 40 pS pulser for risetime test and transient adjustments.http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=295UK L 50. (pre Brexit!)For fast transients, The test setup is critical. Minimum ground return path on the probe is critical, best is a bayonet or direct BNC adapter NOT a wire ground lead.Any constant amplitude RF gen can be used for BW, we use TEK SG503, 191, SG504, etc. The huge classic HP 8640B RF gen is very useful with regulated output 500 kHz - 1250 MHz.2/ For wideband applications > 300MHz the Zo probes such as TEK P6156 are best and go to 3 GHz. These MUST be used with a 50 Ohm scope input and impose a résistive load 500 Ohm...several K Ohm.3/ FET probes are large size and easy to blow the FETs and impossible to fix. Many on epay are damaged or missing tips etc.4/ for 300..500 MHz scopes and plugins, suggest TEK 6137, best compromise in size, BW and ruggedness. Many tip adapters available. Other similar TEK 10X are too delicate or worse response.5/ 10X: CHeck scope input capacitance, vs probe spec, 10x probes have a range of allowed Cin that the compensation will accommodate.eg P6137 is for 246x TEK and 15 pF.6/ Avoid switched probes with 1X/10X, never reliable switches and often poor quality or poor 10X response.7/ We never needed 1X probes: Use a BNC with coax, connect direct. RG178 is 50 Ohm and ~ 0.125" ~ 2 mm dia. Works on either 1M or 50 Ohm input.8/ High voltage probes are a different animal with many uses and precautions. Beware of Freon requirement in TEK P6015 1000x.9/ For professional or serious application, especially if high power or regulatory compliance is involved, strongly suggest to avoid the cheap Chinese knockoff junk and stick to Tektronix probes. Yokogawa are a very good alternative.10/Just the ramblings of an old retired EE!HAPPY PROBING AND FINE HOLIDAYS TO ALLJon

author: nctnico
author_rank: Super Contributor
timestamp: December 20, 2020, 10:50:16 am
content: Quote from: tggzzz on December 20, 2020, 08:53:38 amNo. I don't get why people keep bringing up fast edges to check oscilloscope bandwidth. It is not a 100% correct method because not all oscilloscopes adhere to the factor 0.35 for the steepness of the edge. The only way is to use a levelled signal generator.

author: tggzzz
author_rank: Super Contributor
timestamp: December 20, 2020, 11:13:02 am
content: Quote from: nctnico on December 20, 2020, 10:50:16 amThat's true, but who really cares what a scope's frequency response is?!A scope makes time-domain measurements, and needs to do that accurately. If you want to make frequency-domain measurements, use a spectrum analyser or VNA etc.Where scopes post-process their time-domain information into frequency-domain information, they ought to know and take account of their internal characteristics. For modern professional scopes (i.e. not typical amateur scopes) an "intelligent" probe can also aid removal of distortions in the probe.But in most cases of relevance to people on this forum, the probing technique will dominate all that - and cannot be removed in the scope.

author: tggzzz
author_rank: Super Contributor
timestamp: December 20, 2020, 11:19:36 am
content: Quote from: jonpaul on December 20, 2020, 10:43:42 am... and at even 100MHz those have an input impedance higher than, say, Tektronix P6137 and all the similar onesPlus you can make them yourself and evensolderthem into the circuit. Just solder a 500ohm resistor with short leads directly to the testpoint, and solder a minature coax to that resistor and the ground plane.Note that a typical scope's 20pF input capacitance in parallel with a 50ohm termination is an issue. That's one reason I like my Tek 485: it has a proper 50ohm attenuator on the inputs

author: jonpaul
author_rank: Super Contributor
timestamp: December 20, 2020, 12:12:59 pm
content: Hello again:We make both time and frequency tests with our analog and digital scopes. Reliable specs are important in both domains. We rely on Tektronix and Yokogawa for specified performance in both BW and transient response. We have see many Chinese knockoff scopes and probes that have poor results in either or both areas.1/ Depending on the application, BW or transient resp may be important.Examples: Transient: Testing of high speed digital signal transmission eg transformers and cables.Bandwidth: Checking generator outputs, broadcast exciters and transmitters, etc.Notice that a good BW scope and probe could have a poor transient response and a perfect transient response will not have the widest BWs due to phase response.In CAL of wideband scopes eg TEK 2465/7/B or 7104 + 7A29, transient response is the most difficult and critical adjustment.BW is easier and if transient is good, probably BW is OK after CAL.2/ We also use direct connect with coax. Many wideband and RF PCBs in fine instruments have builtin tiny coax connectors or probe tip receptacles for testing, esp TEK and HP of 1970s...1990s vintage.3/ A well calibrated probe and/or wideband scope should pass BOTH BW and transient tests:0.5 db, 3 db and BW = 6db with 50 Ohm termTransient rise/fall time, abberation, preshoot, overshoot, etc.The pulse source must be verified for fidelity.VSWR of both scope and pulse source will cause reflections and give a worse transient result.Standard practice is to insert a 6 - 20 db wideband attenuator at the scope 50 Ohm input, to attenuate reflections and improve VSWR.We highly recommend the Mini_Circuits BNC><BNC inline attenuators, HAT-xx+ series eg HAT-10+ 10 dB, HAT-20+ 20 db.Specified to 2 GHz.https://www.minicircuits.com/pdfs/HAT-20+.pdf$10 ea VSWR 1.05..1.10.4/ tests that use cables are naturally dependent on the cable transient and BW performance. ALL CABLES ARE NOT CREATED EQUAL!Ordinary coax ><bnc or F or RCA CANNOT be used for calibration or fine measurements! Even USA made Pomona are NOT precision Zo or BW. Let alone the Chinese clone junk calbes.Special calibration coax are available from TEK and GenRad, eg the 0.5m precision 50 Ohm 012-0482-00 BNC><BNC or the Rg8U GenRad 874 hermaphrodit connector 1,2,5,10 nS cablesBest connection is direct eg a BNC F><BNCF adapter and NOT a cable!5/ BNC terms eg 50 Ohm can have issues eg poor quality connectors and inaccurate resistors. The internal construction and type of R determines the BW. Best inline BNC><BNC feedthru are the TEK and Mini-Circuits. The cheapo terms cant be relied on.Enjoy!Jon

author: Finderbinder
author_rank: Regular Contributor
timestamp: December 20, 2020, 01:54:01 pm
content: So many usefull information! Just need endless time to study it all

author: Elasia
author_rank: Frequent Contributor
timestamp: December 20, 2020, 02:25:17 pm
content: Quote from: jonpaul on December 20, 2020, 10:43:42 amJust curious, what's your opinion on RG178 vs RG316?

author: jonpaul
author_rank: Super Contributor
timestamp: December 20, 2020, 03:15:23 pm
content: >>Just curious, what's your opinion on RG178 vs RG316?FinderbinderHave used only RG178/u, normally in 30.....75 cm lengths, so losses were not significant.Searching the comparison, RG316 is much more costly and less flexible and thicker.As its PTFE, harder to terminate.RG316U: Advantage: Mil Spec, 200 dec C temp rations, slightly lower losses.REFS:http://rfcablescoax.blogspot.com/2012/02/rg-316-rg-174-rg-188-coaxial-cable.htmlBelden specs fpr their SKU equiv:https://catalog.belden.com/techdata/EN/8216_techdata.pdfhttps://catalog.belden.com/techdata/EN/83284_techdata.pdfEnjoy!JonPS: Belden has the best info and range. Their app engineer Steve Lampen is the worlds expert on cables.

author: tggzzz
author_rank: Super Contributor
timestamp: December 20, 2020, 03:48:27 pm
content: Quote from: jonpaul on December 20, 2020, 12:12:59 pmProbing technique, especially ground lead inductance, is a major issue at these speeds. I'm sure you know that, but the OP might not.If you have a 6inch/15cm ground lead on a standard passive *10 10Mohm probe, then you will get ringing at ~100MHz. I would be somewhat surprised if a scope could be calibrated to remove that!

author: Elasia
author_rank: Frequent Contributor
timestamp: December 20, 2020, 04:11:33 pm
content: Quote from: jonpaul on December 20, 2020, 03:15:23 pm+1 for Belden, we use their brands for a good bit of stuff, their extreme cables for off highway are fantastic

author: jonpaul
author_rank: Super Contributor
timestamp: December 20, 2020, 04:14:23 pm
content: >>If you have a 6inch/15cm ground lead on a standard passive *10 10Mohm probe, then you will get ringing at ~100MHz. I would be somewhat surprised if a scope could be calibrated to remove that!>>tggzzz: Cal of a SCOPE is different from CAL of the probe. We do scope CAL as per TEK serv manuals. The pulse source is a TD pulser (or we use Leo B 40 ps) DIRECT to scope BNC.Probe CAL is just the LF comp for scope input C. Have never needed to cal HF of a probe.The ground lead length indeed inserts an inductance, which can be calculated or measured.That is why the best probing technique at HF uses a matched coax onboard and Zo matched cable OR if a probe is used, the bayonet adapters that clip at the probe tip and surrounding ground ring. They have NO ground wire.A TEK Zo probe like P 6156 can give fine fidelity above 200 MHz with the proper tip and ground bayonet or adapters.There is NO "calibration" to remove ringing of poor ground return of a probe!Cheers,Jon

author: jonpaul
author_rank: Super Contributor
timestamp: December 20, 2020, 04:19:03 pm
content: We tested 18 types of cables 110 Ohm TP and 75 Ohm coax for broadcast use at 100M legnth for atten and digital sig distortion.Belden 1694A wideband 75 Ohm coax was the best, requires special they F connectors and term tooling.https://catalog.belden.com/techdata/EN/1694A_techdata.pdfJon

author: tggzzz
author_rank: Super Contributor
timestamp: December 20, 2020, 04:27:55 pm
content: Quote from: jonpaul on December 20, 2020, 04:14:23 pmWe basically agree; the differences are probably due to (my) poor use of language.I will, however, note that some *10 passive probes do have HF tweaksinsidethe case. One example is the Tek 6137 - see p6 of the manual on TekWiki.

author: exe
author_rank: Unknown
timestamp: December 20, 2020, 05:13:39 pm
content: How practical is it to poke around with a 10x probe at freqs higher than, say, 100MHz? They load circuit quite a lot.If I needed to see, say, a 500MHz signal, I'd try to gen an active probe, too bad they are freakin' expensive (except may be DIY).

author: 0culus
author_rank: Super Contributor
timestamp: December 20, 2020, 05:19:20 pm
content: Yes, but you're looking at Low-Z probes past 500-700 MHz or so. Keysight offers 10:1 passive probes up to 1.5 GHz. I, personally, have a Tek P6055 low-Z probe and accessories.

author: tggzzz
author_rank: Super Contributor
timestamp: December 20, 2020, 05:42:50 pm
content: Quote from: 0culus on December 20, 2020, 05:19:20 pmI'd suggest a lower frequency than that.I have three HP10020 probes (1.5GHz 0.7pF)

author: 0culus
author_rank: Super Contributor
timestamp: December 20, 2020, 09:11:02 pm
content: Quote from: tggzzz on December 20, 2020, 05:42:50 pmhttps://www.keysight.com/en/pd-1661717-pn-N2873A/passive-probe-101-500-mhz-13-m?nid=-32557.898995&cc=US&lc=eng

author: tggzzz
author_rank: Super Contributor
timestamp: December 21, 2020, 12:41:21 am
content: Quote from: 0culus on December 20, 2020, 09:11:02 pmInput impedance ~j33ohms @500MHz, compared with ~500+j450 ohms for the hp10020.Input impedance ~j67ohms @250MHz, compared with ~500+j900 ohms for the hp10020.I know which I prefer

author: srb1954
author_rank: Super Contributor
timestamp: December 21, 2020, 01:22:36 am
content: Quote from: 0culus on December 20, 2020, 05:19:20 pmAre you sure about the Tek P6055? My catalog says it is a 10Mx10 probe for use with differential amplifiers.Perhaps you have a P6056 or P6057, which are both low-Z probes.

author: 0culus
author_rank: Super Contributor
timestamp: December 21, 2020, 02:43:43 am
content: Yep, off-by-one.

author: Anthocyanina
author_rank: Frequent Contributor
timestamp: December 21, 2020, 07:49:11 am
content: Hi! i thought to ask here about the parts of the probes, i would like to know the "real" name for the detachable hook tip of the probe, and also wondering if they are a standard size for probes of the same bandwidth even if they are from different manufacturers. Ive seen some appear much thicker than others but wonder if that's just an illusion caused by a probe being shorter or longer than other ones. Also, if anyone happens to know where i may find those hook tips online to purchase them without the probe, that would be great. Thank you!

author: BravoV
author_rank: Super Contributor
timestamp: December 21, 2020, 08:21:31 am
content: Quote from: Anthocyanina on December 21, 2020, 07:49:11 amRandom image from GoogleIf you mean the one like above example, yep, they get lost easily, I made my self, use piano/guitar wire, wind it on a stiff steel, such as a nail, but abit smaller in diameter compared to the probe's ground near tip, as it will un-wind a bit by itself, it will be nice fit & snug to the tip, suggesting to do trial and error 1st.Reheat with hot air if needed during the winding at certain wire.Actually copper wire works too, but not as robust as the steel wire, once the winding is done, wrapped it with heat shrink tubing to maintain the tight winding.

author: Anthocyanina
author_rank: Frequent Contributor
timestamp: December 21, 2020, 09:24:39 am
content: Thank you, i meant the grabber part which ends in a tiny hook and has a plastic sleeve around it which you pull back and the hook is exposed

author: rernexy
author_rank: Contributor
timestamp: December 21, 2020, 09:39:38 am
content: Quote from: Anthocyanina on December 21, 2020, 09:24:39 amIn the datasheet for the probes I have Keysight/Agilent names them a "Retractable Hook". Look at the screenshot from the datasheet I've included.

author: Anthocyanina
author_rank: Frequent Contributor
timestamp: December 21, 2020, 08:02:16 pm
content: Great, thank you! now having the name for them will help me find replacements!

author: smaultre
author_rank: Regular Contributor
timestamp: December 22, 2020, 05:46:04 pm
content: Good HF (>300MHz) probe, is a ACTIVE probe,You can combine the TEK 1103 Power, +any TEK P5..6.. active probe,Is the best way, with the lowest cost.

author: todorp
author_rank: Regular Contributor
timestamp: December 23, 2020, 09:34:49 am
content: Slightly off topic. Inspired by this thread I would like to measure the response of my oscilloscope and different probes I have. Can someone describe the setup you are using to perform this measurement. I have geathered diffrent photos from this thread:@jjoonathan@Dexter2I see people use Leo Bodnar's fast pulse generator but do you need any attenuators? Is the rise time of the pulse generator adjustable? Than what exactly is the connector/part where you insert the probe tip?Thanks a lot,Tod

author: todorp
author_rank: Regular Contributor
timestamp: December 24, 2020, 10:58:38 am
content: Ok, I found out what the accessory to connect a probe to a BNC was.But I still have a few questions regarding the measurement:1. If the oscilloscope does not have 50 Ohm input termination should one use external 50 Ohm BNC termination on the scope input?2. Again, are any attenuators necessary?3. Besides qualitative assessements such as "there is ringing" or "the shape of the square wave is distorted" what quantitative measurements does one perform in order to be able to say this scope + probe system is good up to XXX MHz?Any pointers to docs/reading are very welcome.Thanks a lot to anyone who can shed some light,Tod

author: tggzzz
author_rank: Super Contributor
timestamp: December 24, 2020, 11:07:57 am
content: Quote from: todorp on December 24, 2020, 10:58:38 amSee the references athttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

author: exe
author_rank: Unknown
timestamp: December 24, 2020, 11:27:41 am
content: Quote from: todorp on December 24, 2020, 10:58:38 amI measured amplitude of sinewave over a range of frequencies.

author: todorp
author_rank: Regular Contributor
timestamp: December 24, 2020, 11:35:28 am
content: Quote from: exe on December 24, 2020, 11:27:41 amOk, I get that. What about the "fast rise time" square wave tests?Quote from: tggzzz on December 24, 2020, 11:07:57 amThanks @tggzzz I will start reading :-)