FS (UK/World) 7 decades (10K to 10G) resistor set. - Page 1
Forum section: electronics / general

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 20, 2024, 12:31:24 am
content: For some years now I use a small box with BNC sockets and a number of reasonably accurate resistors and find it very useful in many applications. Recently I've made a somewhat better looking copy, so here it is for sale. All resistors will be measured as accurate as I can do it (from <20ppm for 10K to <0.5% for 10G). All BNC sockets are PTFE isolated and the resistor chain leakage to the case is over 1000 Tohm.Resistors used are as follows:10K Vishay Bulk Metal Foil 0.1%, 2ppm/C100K Vishay Bulk Metal Foil 0.1%, 2ppm/C1M0 RC55Y 0.1% 15ppm/C10M Caddock USF340 0.1% 5ppm/C100M Dale RNX 3/8 1% 100ppm/C100M Ohmite Slim-MOX 1% 25ppm/C1G Dale RNX 3/8 1% 100ppm/C1G Ohmite Slim-MOX 1% 50ppm/C10G (2x5G) Ohmite 102E 1% 100ppm/C£150 (UK Pounds) + postage (£5 in the UK, £15 abroad)Please PM me for further details.CheersAlexP.S. the shorting plug isnot includednowincludedin the kit, a 50 Ohm termination plug can also be used in its place (adding 50 Ohm to the chain).P.P.S. The maximum voltage applied to the resistors is 10V for 10K, 30V for 100K, 100V for 1M0, 300V for 10M, 1000V for larger values, the maximum voltage between the case and the resistors chain is 1000V (limited by the BNC connectors) .

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 20, 2024, 01:23:05 am
content: The box as pictured is sold to a forum member (that was quick). I will keep the thread open as I will build more units, so please state your interest here or by PM.CheersAlex

author: krish2487
author_rank: Frequent Contributor
timestamp: July 20, 2024, 07:22:00 am
content: Hello Alex,I m interested if you are willing to take the trouble to make one more. :-)It looks cool and a solid bit of kit btw!

author: Hydron
author_rank: Super Contributor
timestamp: July 20, 2024, 11:17:25 am
content: PM sent expressing interest, but another quick question - do you have the kit to accurately measure the higher value resistors before shipping? Would be especially useful for the >10M ones, as this is tricky to do with a standard bench multimeter.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 20, 2024, 11:26:33 am
content: Quote from: Hydron on July 20, 2024, 11:17:25 amhttps://www.eevblog.com/forum/metrology/precise-measurement-of-high-value-resistors/msg5572707/#msg5572707CheersAlexP.S. - I am making 3 more units, will PM those who ordered, when ready.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 21, 2024, 10:28:09 pm
content: The first unit is packed and ready to go.Measured resistances are:9.9996K99.998K1.00012M10.0012M100.6M1.005G10.035GCheersAlex

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 30, 2024, 11:34:40 pm
content: Two more units are sold, I have one more at £100 + postage price, after that I can make them on order at £150 + postage to cover the new resistors cost. The resistors used would be as on the photo attached, with 25ppm/C Ohmite Slim-MOX for 100M and 1G values.CheersAlex

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 31, 2024, 01:50:16 pm
content: The last unit for £100 isprovisionallysoldto a forum member, from now on the price will be £150 (still essentially a cost price for the box, resistors and connectors) + postage, please PM me for ordering.CheersAlex

author: ause
author_rank: Newbie
timestamp: August 01, 2024, 11:23:40 pm
content: Hi Alex,Apologies for the newbie question but why do you use the BNC jacks vs using Banana jacks, is that for a specific purpose, RF or calibrating?Cheers.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 01, 2024, 11:55:07 pm
content: Quote from: ause on August 01, 2024, 11:23:40 pmGood quality BNC connectors (PTFE isolation, Beryllium Bronze central contact, machined body, not the cheap crap you can buy on eBay etc and not the cheaper versions from decent makes but with Nylon isolation) are probably the only affordable option suitable for this application with the high value resistors up to 10G.Most if not all 4mm binding posts are far too leaky to use at Giga-ohm rangeand do not provide sufficient screening. The nice bonus is that BNC connectors double as high quality mounting supports for the resistors. The solid Al alloy case levels the temperature gradients, reducing possible thermal offsets to essentially insignificant levels for most measurements. At the bottom end the added contact resistance of a quality BNC connector is sufficiently small (milliohms) to provide a good accuracy at 10K (10mohm = 1ppm from 10K).Also this box is primarily a reference set, it has many other uses, including a high voltage divider, a set of external precision resistors for a picoammeter, both as a feedback and in series with the input. Just as an example: using 10G+100M at the input and 10M+1M in the feedback loop you convert a picoammeter into an accurate HV buffer for a voltmeter with 1000V input range, 1V output, and 11G input resistance. And for this kind of arrangement BNCs are the best option.CheersAlex

author: ause
author_rank: Newbie
timestamp: August 02, 2024, 12:05:35 am
content: Nice one thanks Alex..Now that I know all that I should've got in earlier, I'll have to save up a bit more now..Thanks again for your reply..

author: unseenninja
author_rank: Regular Contributor
timestamp: August 02, 2024, 07:30:16 pm
content: The first one of these boxes is now in my hands. Thanks to the thorough packaging, it survived the trip from the UK to Sweden unscathed.As far as I can tell (with an 8.5 digit Datron 1271 meter), the resistances are unchanged by the journey. Shipping in winter might be a different story. My measurements match up well with the original measurements by Alex.Value My Measurement Original Measurement10K 9.999,557,8KΩ 9.9996KΩ100K 99.998,389KΩ 99.998KΩ1M 1.000,127,42MΩ 1.00012MΩ10M 10.001,39MΩ 10.0012MΩ100M 100.575,9MΩ 100.6MΩ1G 1.003,812GΩ 1.005GΩThe agreement between my measurements and the original measurements diverges as the resistance rises. This is caused by a problem which was present in my 1271 when it was last adjusted and calibrated. It was great to see Alex's accurate calibration expose what I already suspected.I can't, at the moment, give a measurement for the 10GΩ resistor - my Datron doesn't go that far and my Keithley 617 needs adjustment and recalibration.If you need a well constructed and well thought out resistance decade that goes from 10K to 10GΩ and comes with an accurate calibration, then I can recommend Alex's resistor set without hesitation.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 06, 2024, 10:33:49 pm
content: The new look for the "7D" - hopefully an improvement, as I keep receiving requests to build more. The label has an acrylic lamination so should survive even an IPA wipe.CheersAlex

author: EC8010
author_rank: Frequent Contributor
timestamp: August 08, 2024, 05:30:13 pm
content: The pedant in me has to point out that kilo should be lower case "k". Upper case "K" is kelvin. Other than that, very nice.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 08, 2024, 09:35:49 pm
content: Quote from: EC8010 on August 08, 2024, 05:30:13 pmI guess it shows my age! When I’ve learned the craft, a capital K was used happily for kOhm. Let’s just hope it won’t mislead anyone.CheersAlexP.S. - two more units are sold to forum members.

author: krish2487
author_rank: Frequent Contributor
timestamp: August 09, 2024, 04:32:50 pm
content: Received a very well packed and robust kit from Alex.Thank you very much Alex!I m no voltnut but a preliminary measurement with a 34460a shows that the measurements are off slightly on some higher ranges (10M and above) and more or less as specifiedon the back of the case for the lower ranges ( some noise in the least significant digit).But,1. I have to subtract 50 ohms from the measurement.2. cables were long and added significant error and are a mess3. the box was cold to touch due to transit, I ll check again tomorrow after the box has settled in this environment.4. I need to rig up a 4W measurement and short cables to make a more accurate measurement.5. the 34460a only goes upto 100M

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 09, 2024, 05:15:58 pm
content: Thank you!Quote from: krish2487 on August 09, 2024, 04:32:50 pmNo, the plug you've received is a true short (less than 0.01 Ohm), not a 50 Ohm termination.CheersAlex

author: krish2487
author_rank: Frequent Contributor
timestamp: August 09, 2024, 06:19:41 pm
content: Great!! :-)I ll keep that in mind..the BNC connectors look and feel top notch and the sticker with the measured values is priceless! :-DThanks again Alex!

author: krish2487
author_rank: Frequent Contributor
timestamp: August 12, 2024, 04:04:22 pm
content: Okay.. so I got some of the stuff over the weekend and gave another spin.The measurement setup is as follows ->2 multimeters - keysight 34460a and fluke 8845, both set to 100 plc and 6.5 digits. readings were taken after allowing the meter to settle for a minute.I used a off the shelf BNC to dual banana plug and connected 4 cables of 50cm length in 4W measurement mode. The cables had stackable banana plugs on either ends.and these is what I measured.Marked Measured9.9997K 9.99653K99.994K 99.7283K1.00038M 1.00008Mand for some reason any measurement above that simpy reads around 5M.. no matter which resistance I try to measure..I m almost certain the cable length is still a huge factor here and the BNC to banana adapter as well..I tested it on both the multimeters and granted, I do not know anything about the calibration on either of them but they seem to agree with each other to a few (tens) of counts.@Alex Nikitinany suggestions on what I can try to measure some of the higher ranges ??I m reasonably happy with what I m seeing on the meters now, I m less worried about the absolute readings and more about the meters agreeing with each other, which they do. :-)I just want to validate it on the 10M and 100M ranges and I will be relieved. :-D

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 12, 2024, 04:11:02 pm
content: Something is not right, perhaps you are connecting the earth side in more than one point. Could you post a photo of your setup? Try to use a simple 2W ohms first, it will add about 0.5 Ohm or less to the value so the error will go progressively less with the increase in resistor value.CheersAlexP.S. - for the right way of connecting to 4W Ohm, look at the post #5 above.

author: krish2487
author_rank: Frequent Contributor
timestamp: August 12, 2024, 04:41:27 pm
content: Thanks for the input Alex.I redid the connections and tried again. with 2W and 4W.. and I tested it on the 10M resistor and I m still seeing about 3.5M

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 12, 2024, 04:48:23 pm
content: What the meter shows if you unplug the BNC?CheersAlex

author: krish2487
author_rank: Frequent Contributor
timestamp: August 12, 2024, 04:49:22 pm
content: ohhhhkay...It shows the same reading as when it was connected.. 3.5-3.6M ohm...

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 12, 2024, 04:55:50 pm
content: I'm not sure what else to try. What happens if you ground the case? If you have a BNC socket to 4mm banana plugs, you could try it with a screened BNC-BNC cable. It is not that much could go wrong with the box. Open it and have a look, perhaps something has wriggled its way in during the transportation... .CheersAlex

author: krish2487
author_rank: Frequent Contributor
timestamp: August 12, 2024, 05:10:07 pm
content: I ll try and check Alex..Thank you once again for the inputs.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 12, 2024, 05:19:14 pm
content: As a possibility- a heavy condensation internally, if the box came from cold into a warm and humid environment, the box is not sealed. Still unlikely in my opinion. Open it and have a look, if needed, dry it at an elevated temperature, the box would happily survive 100C.CheersAlex

author: krish2487
author_rank: Frequent Contributor
timestamp: August 12, 2024, 05:25:42 pm
content: Okay.. I opened the box and it looks normal. no signs of condensation or any such thing. and the resistors were very well soldered. :-)No signs of any broken contact.I did measure the resistance directly at the resistors using a handheld fluke 287 and keysight 1242a - for the 10M and 100M resistors and I ended up reading 9.978M and 97.8M.I did not expect the handhelds to do any better. but it indicates that the resistors are infact okay.( I made two measurements - one directly at the resistor legs and one one the adjacent resistor legs after the BNC to verify that there was nothing broken at the BNC connector itself.)It looks like there is something amiss in my measurement setup.. I will have to check the instruments and the measurement setup once again...Its not like there is anything to go wrong with the box - especially after checking

author: HighVoltage
author_rank: Super Contributor
timestamp: August 12, 2024, 05:54:38 pm
content: Quote from: krish2487 on August 12, 2024, 04:49:22 pmThen you most definitely have a problem in your BNC to banana plug adapter.

author: krish2487
author_rank: Frequent Contributor
timestamp: August 12, 2024, 06:11:36 pm
content: You hit the nail on the head!!I measured the resistance across the banana plugs and I was reading a little over 6M.Measured between the BNC centre pin and the outer body - same.I checked the resistance for another BNC connector I had lying around and it was open...I just got the adapter today!! and I did not even bother to take the receipt.. being supremely confident that nothing can go wrong in such an adapter.Murphy I tell ya!!

author: Kjelt
author_rank: Super Contributor
timestamp: August 12, 2024, 06:32:56 pm
content: I was going to say that as well but 4M is pretty low. I had adapters at around 100M so not suitable for large resistance measurements. As Alex pointed out in his post, the kind of plastick , nylon, pom etc used is critical for very hig ohms measurements. As well as contaminants such as oil from your fingers and humidity.

author: krish2487
author_rank: Frequent Contributor
timestamp: August 12, 2024, 07:10:18 pm
content: The higher ohms 1G and above are pretty much not possible as the multimeters at my disposal cap out at 100M.but it is nice to know the gotchas even in the Mohm range. :-)I ll invest in some quality connectors.. and maybe build shorter cables as well.

author: Hydron
author_rank: Super Contributor
timestamp: August 13, 2024, 03:10:20 am
content: I've had issues with leaky adapters too but in the giga-teraohm range - in the megohms is pretty terrible!

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 13, 2024, 11:27:07 pm
content: It is a horribly badly made or contaminated adapter. I have several similar adapters here and they all measure about 10 Tohm, not perfect but good enough for most measurements up to 10-100M.CheersAlexP.S. two more units are sold to forum members.

author: unseenninja
author_rank: Regular Contributor
timestamp: August 14, 2024, 07:57:06 am
content: I received a very similar and very useless BNC to banana adapter from Amazon...

author: HighVoltage
author_rank: Super Contributor
timestamp: August 14, 2024, 08:49:13 am
content: Quote from: unseenninja on August 14, 2024, 07:57:06 amOne has to wonder, what kind of material they are using.I would take it apart and look for the area that is causing this breakdown.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 14, 2024, 08:50:58 am
content: I just wonder what plastic is used in this rubbish, even PVC wouldn’t have such a low resistance! I had a reasonably good luck with BNC to BNC cables from Amazon when I needed them in a hurry, however it looks like the adapters could be a minefield. The ones I use were bought from RS and Farnell.To make life a bit easier from now onI’ll offer a free BNC shorting plug with each unit(as a couple of buyers did ask for it and already received such a plug). It is also worth noting that for higher resistances (1M and more) a 2W Ohm measurement with a coaxial cable and a BNC to a dual banana plug adapter is a better way of connecting.CheersAlex

author: SeanB
author_rank: Super Contributor
timestamp: August 14, 2024, 12:53:27 pm
content: Quote from: HighVoltage on August 14, 2024, 08:49:13 amI would say the black colour is the issue, as it generally is carbon black blended into the plastic, so it has a very high resistance, but is still conductive in thin areas, even if it will withstand 500VDC testing without passing appreciable current. Better ones use different materials, possibly black iron oxide powders, which provide higher resistance, though the best is plain natural PVC, or even better nylon or PTFE, which is a lot more expensive. More expensive adaptors only have the black as outer cover, inner is made with virgin uncoloured HDPE, and there is a gap between the metal parts and the connectors.

author: Zucca
author_rank: Unknown
timestamp: August 14, 2024, 01:13:48 pm
content: Thanks I will check mines... the devil always hides in details.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 14, 2024, 01:29:52 pm
content: man quality as gone down the drain....had problems with bnc to sma cables lately, same resistance effects .... mostly intermittant

author: Zucca
author_rank: Unknown
timestamp: August 14, 2024, 02:01:27 pm
content: IDEA:krish2487I would post big pictures of the affected adapter and open a new thread in the "General technical Chat" section or "Test Equipment".I can imagine many people are using them without knowing they are bad.

author: Kjelt
author_rank: Super Contributor
timestamp: August 14, 2024, 02:40:56 pm
content: It is almost as low as ESD safe plasticks

author: krish2487
author_rank: Frequent Contributor
timestamp: August 14, 2024, 03:54:51 pm
content: @ZuccaThats a good idea actually.. I ll do that over the weekend..Bear in mind, the pics are from an iphone.. so they may all not be all that great.. but I will try my best.

author: unseenninja
author_rank: Regular Contributor
timestamp: August 14, 2024, 04:00:29 pm
content: Quote from: SeanB on August 14, 2024, 12:53:27 pmIt's not the plastic. I ordered two adapters. One has 2M between the terminals, the other has > 1G.Most likely, the connection between the BNC plug and the 4mm sockets is made in a less than optimal way and when the assembly is put inside the moulding machine to add the plastic, it causes a partial short to develop.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 14, 2024, 07:06:05 pm
content: Quote from: unseenninja on August 14, 2024, 04:00:29 pmBy the way, one of the benefits of having a calibrated high Ohm resistor array is that you could at least try to estimate much larger resistances than your meter can measure, by connecting the unknown in parallel to 1G resistor and observing the difference. This way you should be able to see the effect of values up to 100G, possibly more. For starters you could try it with the 10G resistor in the array and see how accurate it can be.CheersAlex

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 18, 2024, 12:02:23 am
content: I've started aseparate thread in the Metrology sectionto show some TC measurements and to discuss application matters as it would be more appropriate than here.CheersAlex

author: EC8010
author_rank: Frequent Contributor
timestamp: August 18, 2024, 10:42:05 am
content: Those poor adapters put the willies up me as I use BNC-4mm adapters a lot. I've just been through my ten adapters and they were all >1G.

author: HighVoltage
author_rank: Super Contributor
timestamp: August 18, 2024, 11:28:48 am
content: Many years ago I had contact problems with BNC to Banana plug adapters.Then I switched to Stäubli / Multi Contact / MC brand and never had any problems again.Especially for any kind of metrology grade measurements, these adapters are perfect.

author: zepto
author_rank: Regular Contributor
timestamp: August 18, 2024, 04:58:23 pm
content: I bought a set of 2 bnc->banana adapters 2.5 years ago from amazon, maybe the same ones. One had 1Mohm resistance and the other had 10Mohm, so it was possible to identify them as trash using the cheapest multimeter. They were plastic waste the second they were produced. There were no bad reviews so amazon must delete them. I just mean to say this isn't some one off bad batch thing, they have been selling useless trash for years uninhibited. I threw them away and bought some Philips adapters that were probably 30+ years old and still tested good with an electrometer.Since then I have not bought a single piece of amazon/ebay JDAOIDJS chinesium test cabling/adapter. I won't buy banana patch cables or even insulated wire from these morons. I passionately avoid giving them business. The one advantage of these trash vendors filling ebay with garbage is that people will sometimes sell surplus cables for a decent price. I bought a used set of 30x minigrabber to minigrabber cables for $30. They were all ez-hook/pomona. I just cut one in half whenever I need to build another banana-> minigrabber cable. They are high quality and they will probably outlast me.I am sorry to further derail your listing. I'll take one if you are making more.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 18, 2024, 05:09:27 pm
content: Quote from: zepto on August 18, 2024, 04:58:23 pmYes, I’m making more of these boxes, PM me for details if you would like to order one.CheersAlex

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 24, 2024, 10:44:22 pm
content: Three more boxes (with a silver plated BNC shorting plug) are available (one from the photo is already going to be posted on Monday).CheersAlex

author: guenthert
author_rank: Frequent Contributor
timestamp: August 25, 2024, 08:34:49 am
content: I received an unit well packed and better made. The listed values (on the bottom, to discourage cheating ;-) near perfectly matched my measurements using my Datron 1271 (up to its maximum range of 1GOhm), the ones of the high value resistors matched closely my measurements using my Keithley 617. Neither of my instruments had been calibrated in the ~7 years I own them and probably not for a much longer period. I had already good reasons to suspect that my Datron was more accurate than I could reasonably hope for, but I had no idea that the Keithley was so close (well, within specifications, which of course became meaningless decades ago).I used multiple of those resistors to validate the linearity of the Keithley 617 (validating the linearity of the Datron 1271 is beyond my skill and means, I'm afraid).Imho a neat tool for those interested in high resistances / low currents.

author: guenthert
author_rank: Frequent Contributor
timestamp: August 25, 2024, 08:41:23 am
content: Re: BNC->4mm terminals: in my collection of adapters I found a no-name unit and using a Keithley 617 measured it's insulation between conductors to be around 129GOhm (probably should clean it and re-measure, but I don't have pure alcohol readily available -- the content of the bottle I had completely evaporated during the last five years).I also found a Ponoma 1296 which clocked in at a whopping >500TOhm. One gets what one pays for, I guess.EDIT: My Keithley 617 is suffering from excessive input bias current and awaits repair; readings of >1TOhm are highly suspect. Still I'd think the isolation of the Ponoma to be much higher than of that no-name adapter referred above.

author: Hydron
author_rank: Super Contributor
timestamp: August 25, 2024, 11:55:05 pm
content: My own bad adapter turned to be worse than I though, but putting 1100V (hitting the 10mA limit, actual voltage unknown but probably a few W dissipation) across it seems to have burnt the worst of the leakage away(it's still not amazing, but was leaking milliamps when you turned up the voltage up beyond a few hundred V earlier, now just in the ~1uA range @ 1kV)

author: krish2487
author_rank: Frequent Contributor
timestamp: August 29, 2024, 01:54:19 pm
content: @Alex NikitinMy apologies for the lack of a follow up response until now.I had a few pomona 1296 on order and I was waiting for them to show up.And I m happy to report on my findings! :-)The same test setup as before, plcs, settling time and the 4W measurement method suggested by you.These are what I measured on the 34460AMeasured Marked on the back of the unit9.99991K 9.9997K99.9939K 99.994K1.00038M 1.00038M10.00344M 10.0032M100.4514M 100.4MSo pretty much spot on! :-) Unfortunately I cannot measure greater than 100M on any of the meters I have with me..

author: guenthert
author_rank: Frequent Contributor
timestamp: August 30, 2024, 09:10:09 am
content: Quote from: krish2487 on August 29, 2024, 01:54:19 pmYou could place the meter in voltage function with 10MOhm impedance and use it as a voltage divider with the DUT, then apply a known (preferably high) voltage. The internal "10MOhm" resistance varies wildly in cheap hand-held DMMs, but should be fairly close to nominal in a bench meter. Don't expect ppm accuracy, but closer than 0.1% (which you can verify with the 10MOhm resistor as DUT you measured earlier).

author: Alex Nikitin
author_rank: Super Contributor
timestamp: September 30, 2024, 05:29:09 pm
content: UpTwo more boxes are available.CheersAlex

author: Alex Nikitin
author_rank: Super Contributor
timestamp: January 08, 2025, 04:26:22 pm
content: The last box of the batch I've built in August is SOLD. I will build more soon, please state your interest here.CheersAlex

author: Alex Nikitin
author_rank: Super Contributor
timestamp: May 16, 2025, 11:45:14 pm
content: Two more boxes are available, now can be verified with a freshly calibrated Keysight 34465A. Please PM if interested.CheersAlex

author: voltsandjolts
author_rank: Unknown
timestamp: May 17, 2025, 07:22:41 pm
content: Hi Alex,I'll take one please. See PMs shortly.Cheers.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: May 18, 2025, 10:10:44 am
content: One box is now sold.CheersAlex

author: voltsandjolts
author_rank: Unknown
timestamp: May 27, 2025, 09:30:51 am
content: Thanks Alex, well packed, quick post and nicely built

author: exe
author_rank: Unknown
timestamp: August 29, 2025, 08:03:45 pm
content: Thank you, Alex, for this wonderful resistor kit. I finally have time to play with it and it's very useful to calibrate my picoammeter.

author: neverendingstudent
author_rank: Regular Contributor
timestamp: August 29, 2025, 08:46:49 pm
content: EDIT: I apologize, I replied without noticing this topic already had 3 pages of replies and that you already had this figured out. My bad.Quote from: krish2487 on August 12, 2024, 04:49:22 pmIf you're reading the same ~3.5Mohm with that setup while the BNC is unplugged from the resistance box, then I have 2 ideas:Idea 1: the 34460A is reading incorrect resistance in 2-wire mode while being physically connected with 4-wire. Recommendation: try unplugging the secondary plug set and only measure with actual 2 wires connected.Idea 2: the BNC to banana jack adapter may be poorly made with regards to high-impedance specs and may actually have a ~3.5Mohm resistance internally. Recommendation: try a different (preferably different brand/source) BNC to banana adapter.

author: krish2487
author_rank: Frequent Contributor
timestamp: August 29, 2025, 09:21:34 pm
content: Quote from: neverendingstudent on August 29, 2025, 08:46:49 pmNo worries... :-)All good... its always better that these kinds of threads are periodically revived to sort of jog the memory of others to eliminate the simplest culprit first.. :-D

author: EC8010
author_rank: Frequent Contributor
timestamp: August 29, 2025, 10:39:27 pm
content: Annoyingly, calibrating a Keithley 2000 requires a 1k resistance in addition to those Alex's box can do.

author: Hydron
author_rank: Super Contributor
timestamp: August 30, 2025, 01:37:55 am
content: I've got a plan to build a second lower resistance box in a similar style, though it will need 4 wire terminals (already marginal for 10k not having them). The series string config complicates the terminal config unfortunately - need to think on it.What I should really also do though is make a box for my salvaged fluke 335D resistor string and it's hermetic wire wounds, that's a really bling 7 decades...

author: guenthert
author_rank: Frequent Contributor
timestamp: August 30, 2025, 07:12:08 am
content: Quote from: EC8010 on August 29, 2025, 10:39:27 pmWell, it's my understanding that this is meant for high resistance / low current circuits; not expressively for calibration, certainly not for calibration of general purpose long scale DMMs (some want a resistance for every decade, including 100Ohm, but none would ask for 10GOhm).I otoh, would have wished for a 100GOhm resistor, as that would be handy for calibration / performance check of a Keithley 617. Those aren't cheap however and would have driven cost up and benefited only a very small set of customers. (I could buy ten 100GOhm resistors and compare each with the one of the box ...).I'm quite happy as it turned out.

author: Hydron
author_rank: Super Contributor
timestamp: August 30, 2025, 01:17:21 pm
content: You can probably get away without the 100G resistor for the 617 - use either a lower voltage and the 10G resistor, or a capacitor and dV/dt to generate a current (this would miss out the 200G resistance range though, which while not calibrated directly is in the performance check list I think).

author: ballsystemlord
author_rank: Frequent Contributor
timestamp: August 30, 2025, 11:03:23 pm
content: Hello Alex,I was curious about this and read many of the posts. I wanted to make you aware that as frequency increases, those blue Ohmite Slim-MOX resistors have problems maintaining their resistance values. Mind, I'm talking khz, not mhz, or ghz frequencies. I'll post a demonstration with photos later if you'd like.

author: exe
author_rank: Unknown
timestamp: August 31, 2025, 07:38:58 am
content: > I'll post a demonstration with photos later if you'd like.I do)

author: EC8010
author_rank: Frequent Contributor
timestamp: August 31, 2025, 12:12:02 pm
content: Quote from: ballsystemlord on August 30, 2025, 11:03:23 pmOh yes, you don't need much shunt capacitance across a 100G resistor to severely upset frequency response. After all, 4pF//100G is 0.4s!