Decade resistance box re-prupose to DIY 10:1 and 100:1 transfer divider - Page 1
Forum section: electronics / general

author: VintageNut
author_rank: Frequent Contributor
timestamp: September 25, 2016, 08:12:06 pm
content: I have a 6-decade resistor substitution box that I am considering trying to use as a 100:1 and 10:1 transfer divider.The resistors appear to be very tightly matched. The date code on all of the resistors are 1966 so they have been gracefully aging for 50 years.The lowest decade is 1 ohm per step and the highest decade is 100k ohms per step. The 100k resistors all appear to be better than 100ppm from nominal after 50 years and much closer to each other than 100 ppm.My thought is to add binding/banana posts on the case and wire the posts to the 1.0, 0.1 and 0.01 taps on the switches. Then trim the voltage drops to make exactly 0.1 and 0.01 of the input.My first experiment is to characterize the decade box without any surgery. Just use the first 3 decades to make resistances that show the parts that will be sections of the final divider configuration.Below are the results of the experiment. I used a Keithley DMM7510 on the 1-megohm range. The DMM was warmed up for over 90 minutes which is required to perform AutoCal. I performed AutoCal and began. The results look very promising. It looks like I just have to trim down the bottom 10K by 15ppm and trim down the next 90K by 6 ppm. The 90k trim will affect the 0.01 ratio but i calculated that the effect will be less than 0.1 ppm of the 0.01 ratio.We shall see when I order and receive the binding posts to take the voltage measurements.Any suggestions are welcomed.Dial Numerical Measured Total Stack position Stack ResistanceSetting Setting Meg Ohms PPM over resistor From botom up000000 0.00 0.0000000X9X000 1.10 1.1000584 53.09 100003.60 1100058.499X000 1.00 1.0000548 54.80 100006.20 1000054.889X000 0.90 0.9000486 54.00 100006.20 900048.679X000 0.80 0.8000424 53.00 100003.40 800042.469X000 0.70 0.7000390 55.71 100007.20 700039.059X000 0.60 0.6000318 53.00 100004.20 600031.849X000 0.50 0.5000276 55.20 100003.70 500027.639X000 0.40 0.4000239 59.75 100006.60 400023.929X000 0.30 0.3000173 57.67 100006.90 300017.319X000 0.20 0.2000104 52.00 100004.30 200010.409X000 0.10 0.1000061 61.00 90005.40 100006.100X000 0.01 0.0100007 70.00 10000.70 10000.7

author: zlymex
author_rank: Frequent Contributor
timestamp: September 26, 2016, 12:27:19 am
content: It seems to me quite feasible. What is the brand or type of the substitution box?Upside:- very little work to do to use it as a divider- if the total nominal resistance is 111111 Ohms, then, in theory, the first switch tab(100k) will give the 10:1 divider output and the second switch tab(10k) will give the 100:1 divider output. These assume that the ground is used as ground(not 0.01 tab used as ground).Downside:- the measured Ohms is not directly reflect the divider ratio because of the lead and internal(wire and switch contact) resistance.- the variation of contact resistance of the switches may affect the divider ratio.- there is a limit of the maximum input voltage depending the spec of the substitution box.- trimming will void the functionality as the substitution box.

author: VintageNut
author_rank: Frequent Contributor
timestamp: September 26, 2016, 01:05:34 am
content: The brand is General Resistance, model RDS-65M. The resistors look to be almost exactly the same as what are in my General Resistance DV-4107 7-decade KVD. The difference is the in the KVD, the resistors are grouped by batch, each group has a serial number, and are exactly equal.In this resistance box, zero is really zero. You can see this with the DMM7510 when switching from 000000 to 000001.I have just finished reading the Fluke 752A manual and read Dr. Franks explanation and discussion of his home-brew 752A. I could re-configure the first three decades to be exactly like the Hamon dividers that are in the 752A. I would not use one of the 100k and one of the 10K.If I set the controls to 10-10-10-10-10-10, the resistance is 1.11111. The two ratios on the top of the second and third decade will be0.01111/1.11111 = 0.0099990110.00111/1.11111 = 0.00099901I do not think that will work.What I think can work is 9-9-9-9-9-10 and 9-9-9-9-10-0 and 9-9-9-10-0-0 and 9-9-10-0-0-0If the setting is 9-9-9-9-9-10, you can obtain 0.1, 0.01, 0.001, 0.0001 and 0.00001

author: zlymex
author_rank: Frequent Contributor
timestamp: September 26, 2016, 02:23:58 am
content: Quote from: VintageNut on September 26, 2016, 01:05:34 amAnother way is to add an resistor of 0.111 Ohm to the ground and a binding post, it will be Ok in theory, and the original function(as a substitution box) is also preserved.

author: VintageNut
author_rank: Frequent Contributor
timestamp: September 26, 2016, 03:16:15 am
content: That makes sense. I can set all the dials to 10 and then add the resistance that causes all of the decades to be 1/10 of the voltage of the decade on the left. Nice idea.Here is the frontHere is insideThe resistors are beautiful. The wiring and soldering look good enough to be military. The ppm matching in each decade and ratios between decades are amazing.No matter what configuration I decide to use, there will be a change needed. I will try the smallest change to run some test but I may decide on a Hamon configuration for a final working unit.

author: zlymex
author_rank: Frequent Contributor
timestamp: September 26, 2016, 03:37:56 am
content: Those resistors look similar to the one in GR RTD 100 Simulator, and similar to GR 105T transfer standard

author: Vgkid
author_rank: Super Contributor
timestamp: September 26, 2016, 04:34:51 am
content: That RDS-M looks similiar to one I almost bought on ebay last year..Here is a manual for that model.

author: VintageNut
author_rank: Frequent Contributor
timestamp: September 26, 2016, 11:22:15 am
content: Quote from: DiligentMinds.com on September 26, 2016, 03:27:37 amWhich brings up the question: How do you measure what the ratio of the un-adjusted divider is? It appears that the adjusted and balanced 752A is the most accurate divider for the performing the 100:1 and 10:1 transfer of a known standard to a different decade.The only instrument in my lab that I can compare the divider to is one of my two General Resistance KVDs.From my reading, the 752A style divider can be adjusted to be more exact than a KVD for the 10:1 and 100:1 transfer because of the Hamon trick and the built-in reversible Wheatstone bridge with fine balance control.If I make the divider non-adjustable, then my KVD is more accurate and I may as well just use the KVD for the 10:1 and 100:1 transfer.Just my thoughts on this topic. I am willing to be swayed a different direction with proper logic.

author: VintageNut
author_rank: Frequent Contributor
timestamp: September 26, 2016, 11:24:56 am
content: Quote from: zlymex on September 26, 2016, 03:37:56 amGen Res is "General Resistance". They obviously sourced these resistors to competitors. Very interesting. Thanks for sharing the pictures.

author: VintageNut
author_rank: Frequent Contributor
timestamp: September 26, 2016, 11:30:15 am
content: Quote from: Vgkid on September 26, 2016, 04:34:51 amThanks for the manual!

author: Dr. Frank
author_rank: Super Contributor
timestamp: September 26, 2016, 12:39:13 pm
content: Quote from: VintageNut on September 26, 2016, 11:22:15 amThat's the Hamon trick, also: In the 1:1 Wheatstone / calibration configuration, the deviation from exact balance is the same, as in the 10:1 configuration.This is done in the Fluke 5440B, see description in the service manual, theory of operation, and in the appendix. They determine this ratio deviation by measuring the bridge voltage output, and later apply this same value as a correction factor for the 1:1, 2:1, 25:1 and 100:1 divider configuration.Quote from: VintageNut on September 26, 2016, 11:22:15 amThese reference (Hamon) or ratio (KV) dividers, require a frequent re-adjustment, at best each time before usage.Otherwise, thermal or timely drifts will for sure deteriorate the precision.That's the same 'good metrological practice', as for other Auto-Calibration instruments, like 3458A, 5720A, and the 5440B, which should be auto-calibrated at least once per day, or whenever ambient temperature changes more than a specified limit, e.g. 1°C.Therefore, a (single) comparison by means of another ratio instrument makes no sense. Routine comparisons are unpractical, as you then could better use the other ratio instrument directly. Also, your 10:1 divider will be less precise than the other dividers used.Instead, you need to implement a Wheatstone Bridge directly into your divider, and either use the Hamon trick, or the resistor-comparison scheme of the KV 720A. Both can be used to calculate the real 10:1 / 100:1 divider factors, instead of adjusting.Anyhow, only the Hamon trick will give sufficient accuracy, when using equipment which is accessible to us amateurs, like a null voltmeter at a few 100nV level, including switches, cables, and so on.There may exist other procedures, as zlymex suggested recently, when we discussed adjustment of such dividers at working voltage level. These may definitely require nV level instruments and components.Another problem with your divider is, that it can only be used for relatively low voltages (maybe a few 10 volts only) to be divided, as otherwise the self-heating of the resistors will definitely bust the adjustment or ratio calculation. See error calculation in the 752A manual, regarding this aspect.Frank

author: VintageNut
author_rank: Frequent Contributor
timestamp: September 26, 2016, 02:29:37 pm
content: Hello Dr. FrankThank you for replying. That very makes sense that the Wheatstone bridge must be inside the divider and that the bridge must be checked for balance and divider must be calibrated every time it is used.I have a few questions about your DIY divider.1. Do you have part numbers for the switches that you used in your divider?2. Do you have pictures of the inside and outside layout of the switches for the divider?3. What voltage do you apply to the input of your divider for transferring range calibrations?The 100K resistors in the box posted above are rated at 2.3mA maximum so they are about 500mW max.What power would you think will be safe to avoid self-heating errors? I will have a look at the 752A error calculation discussion in the manual.One of the things that I want to do is to transfer the 10V setting on my Fluke 731B up to the 1000V source setting on my Keithley 237 and on my Fluke 332A. It looks like I need to join the discussion that you and xlymex are having about working voltage division.Thank you again for answering in this thread.

author: zlymex
author_rank: Frequent Contributor
timestamp: September 26, 2016, 03:07:01 pm
content: Speaking of input resistance for 1000V divider, here are some examples:- Datron 4902S, 1Meg, 1Watt, 200 foil resistors(20k each), 5mW each resistor- Datron 4902, 1Meg, 1Watt, 100 foil resistors(10k each), 10mW each resistor- Fluke 752, 4Meg, 250mW, roughly 33 WW resistors(120k each), 7.5mW per resistor- Fluke 5440B, 2Meg, 500mW, 10 WW resistors(200k each), 50mW per resistor, ovenized- Fluke 335D, 1Meg, 1Watt, 10 WW resistors(100k each), 100mW per resistor- Fluke 720A, 100k, 10W, 40 WW resistors(2.5k each), 250mW per resistor, oil filled tankAs an old rule of metrology, 10mW per resistor is the standard power. This may be increased if the requirement is not too tight or the TCR is very small or there is a way to dissipate the heat.

author: VintageNut
author_rank: Frequent Contributor
timestamp: September 26, 2016, 05:09:35 pm
content: The string from this decade box would be 1Meg 5 Watt.At 1000V power is 1W for the string and 0.1W for each resistor.In a Hamon configuration, there would be 9 of the 100K resistors running at 0.1WThe bottom of the divider would be 10 x 10k with 10V across each resistor. power is 0.01W in each resistor.If the tempco is similar in all resistors, the 100K resistors will drift more than the 10K resistors configured as a divider.Since i will have to remove the resistors to make a Hamon divider, I can have a try at characterizing the tempco for each part of the string.Maybe an oil bath for the entire Hamnon string will help mitigate the imbalance in power?I like Dr Frank's string of 100 resistors. The power is equal in every resistor.Sadly, I do not have qty 100 of the very tight ppm 10k value resistors in the decade box. Only 10 of each value.

author: VintageNut
author_rank: Frequent Contributor
timestamp: September 26, 2016, 07:58:49 pm
content: Quote from: DiligentMinds.com on September 26, 2016, 06:12:40 pm5ppm ratio characterized how? Day-to-day? Over some temperature range? Or over some voltage range?This should be easy to prove or disprove if the divider is constructed in the Hamon configuration with a proper Wheatstone bridge. Leave the divider alone after initial adjustment and daily daily balance the bridge and check the divider behavior.Do you have other suggestions for stability characterization?For sure this is a learning experience project. At the end, I do hope to be able to check and/or adjust some of my gear that is un-calibrated. My only calibrated instruments are a Keithley 2000 and a Keithley 2750. The model 2000 is 1ppm off on the 10V DC range and 1ppm off on the 1V range. When you look up the Fluke 5700A specs that was used to calibrated my KE2000, the Fluke 5700A best uncertainty for DCV is 7ppm. No need to jump up and celebrate.I do perform some single-ppm measurements. The linearity of the model 2000 is quite good in practice. Per the spec worst case linearity is 1ppm of reading + 2ppm of range. In practice, I can flip every digit of my model 2000 and the digits agree with the reading of my KVD which is fed 10V from a Fluke 731B.I have a DMM7510 which is on loan to me. It is relatively new and is within its 1 year calibration.

author: VintageNut
author_rank: Frequent Contributor
timestamp: September 27, 2016, 01:27:04 am
content: I will report back when I have enough parts on hand to lash up a rudimentary Hamon and a proper Wheatstone with the resistors from the first two or three decades.In the meantime, I am considering how to test for tempco of resistors.What is the normal practice for choosing temperatures to check tempco? I have never done this before.

author: zlymex
author_rank: Frequent Contributor
timestamp: September 27, 2016, 10:04:12 am
content: Quote from: DiligentMinds.com on September 26, 2016, 06:12:40 pmTrue. Datron use VH202C in 4902S. Two VH202C of 20k is better than one VHP101 of 10k in a sense that the former dissipate heat better.Quote from: DiligentMinds.com on September 26, 2016, 09:22:55 pmNo oil tank though, see attached photo.

author: zlymex
author_rank: Frequent Contributor
timestamp: September 27, 2016, 04:00:57 pm
content: I've tested a prototype divider that must be from Fluke. The construction is very similar to 752A, but most of the PWW resistors are 80k in value instead of 120k.

author: Dr. Frank
author_rank: Super Contributor
timestamp: September 27, 2016, 05:45:10 pm
content: Quote from: VintageNut on September 26, 2016, 02:29:37 pm1. It's a switch from ELMA, 04-3264. 6 positions (6-to-1), on 3 planes, 3µm gold plated contacts. It can withstand 500V per specification, and is tested at 1000Veff between adjacent contacts, so careful distribution of the HV lines is necessary. It costs about 83€ in 2004.http://www.elma.com/en-eu/products/rotary-switches/rotary-switching-products/product-pages/type-04-detail/2. A picture can be found here, though it's not useful to reconstruct the schematic, I think:https://www.eevblog.com/forum/testgear/hp34401-measurement-of-linearity/msg358713/#msg358713These cables are PTFE, and you see the 104 EA / 25kOhm resistors, and several trimming thin film resistors, for each of the 7 different partitions of the divider, i.e. 25k, 3 x 75k, 3 x 750k, and the Wheatstone bridge, 2 x 50k.The switch circuit is also balanced for contact resistance.My design is a mix of features from the Datron 4902 (100 MBF resistors) and the Fluke 752A (Hamon type auto-adjustment).Like the Datron 4902, it falls into the category of 'equal temperature rise' of its divider legs.The typical error at 1kV due to self heating for either leg of the divider can be estimated as follows:(power dissipation per resistor) x (heating coefficient) x T.C.4mW x 0.12°C/mW x 1 ppm/°C = 0.5ppmIf both legs have same polarity of T.C., which is more probable, the overall error will further decrease.If they have inverse T.C. of each other, it might add up to 1ppm.1ppm/°C is the typical T.C. for one resistor, which I have measured, but this value might also alternate between ~ 0.2ppm/°C as best case, and 2.5ppm/°C maximum, as specified.Determination of T.C. of the seven different partitions of this divider, and selection of single resistors (requires maybe additional 20 spare resistors), would allow trimming of the overall power error, like it's done for the Fluke 752A.Instead, I made a dynamical 1kV divider test, i.e. monitoring of the change of the 10V output voltage after loading the divider with 1kV.This gave about 1ppm initial drift, as estimated for the typical case.3. Like in the 752A, I use 20V for bridge excitation.I had the very same intention, as you. At that time, I owned a 6 1/2 DMM (34401A), a 10V reference (DIY LTZ1000), a 332B/AF, and I wanted to calibrate 10V, 100V and 1000V ranges of the 332B by transfer from 10V. The 34401s DCV ranges of course could be calibrated also, see that other picture, below the reference divider.If you dive into ppm uncertainty, especially at high voltages, a 'safe' power dissipation value can not be defined, that's the wrong approach.In the 752A, there are no details given for the T.C. and power dissipation matching, I have to admit.Therefore, you have to calculate the thermal drift of the ratio, by analyzing the type of divider you have, and the T.C.s and matching techniques of the resistors, like briefly presented above for my divider.zlymex already has listed many of these HV dividers, and on his bbs.38hot.net almanac, he has nice overview and pictures and analysis of the 752A, already.http://bbs.38hot.net/thread-137-1-1.html(needs google translator, maybe)For the different categories of dividers, by applying similar calculations, or from experiments, I'd like to supplement their estimated 1kV errors.Critic welcome!Frank

author: ebclr
author_rank: Super Contributor
timestamp: September 27, 2016, 06:48:06 pm
content: LT5400B-8Featured 4 2 x 1k, 2 x 9kExcellent Matching– A-Grade: 0.01% Matching– B-Grade: 0.025% Matching0.2ppm/°C Matching Temperature Drift±75V Operating Voltage (±80V Abs Max)8ppm/°C Absolute Resistor Value Temperature DriftLong-Term Stability: <2ppm at 2000 Hrs–55°C to 150°C Operating Temperature8-Lead MSOP Package

author: zlymex
author_rank: Frequent Contributor
timestamp: September 28, 2016, 01:59:55 am
content: Quote from: Dr. Frank on September 27, 2016, 05:45:10 pmThose resistors(from Alpha Electronics) are indeed very good both in term of TCR and tolerance. I got many(4 digits) such resistors too and their actual deviation to nominal value is usually as low as <0.005% for resistors with 0.02% specification. This is also an indication of the very small aging rate, considering those resistors had been made many years before.

author: VintageNut
author_rank: Frequent Contributor
timestamp: September 28, 2016, 12:33:10 pm
content: Thank you Dr. Frank for the links and for the explanation. That helps very much. I have homework to do now to understand better how the 752A is arranged and how it operates.I removed the first two decades from the decade box. I tested the 10k-per-step decade first since it will be at the bottom of the divider. I will skip all the steps for now and just say that the decade is arranged as a 10:1 divider. The bottom 10k resistor requires a series resistor of 2.2//1.0//1.0 to balance the divider as a 10:1. I am performing a coarse check with qty 2 of Fluke 731B. One of the 731B is a 10V source for the divider and the other 731B is a 1.000000 source to check the bottom resistor of the divider string.I have the string of 10K resistors performing as a 10:1 divider with about 1ppm accuracy. This 1 ppm is compared to the 731B sourcing 1.000000v.Before adding any resistors, the 1.0V divider output was low by 35ppm. Adding 1 ohm in series changed the divider to be high by 65 ppm. This arrangement will allow a calibration pot in series with the lowest resistor to balance the divider. I will try a 10 ohm, 20-turn, pot in parallel with a 1 ohm resistor. I can place another small pot in series with one of the upper resistor strings to allow some more fine tuning for the Hamon calibration.Thanks you to everyone who participated in helping me learn some more.

author: VintageNut
author_rank: Frequent Contributor
timestamp: September 29, 2016, 09:20:00 pm
content: I have some news and progress.The resistors in Dr. Frank's design are available in the USA from Trendsetter Electronics in Florida. They are an authorized distributor of Vishay and Alpha Electronics; a Vishay subsidiary.The price for 100 pcs is USD $3.99 each. The resistors are not stocked and have a 12 to 13 week lead time.I have tried the string of 10K General Resistance resistors in two different modes. First I tried adjusting the 10k bottom resistor and monitoring the divider output. This was subject to lots of instability.Next I placed a fixed 1-ohm resistor in series with the bottom 10K and then added resistance to the top 90k. This configuration is much more stable and easier to adjust.The value of resistance to add to the to 90k string to balance the divider is between 4 ohms and 5 ohms. What works best is to have a string of 1 ohm resistors in a ladder on a protoboard and pick off what is needed quickly with solid hookup wire. Currently have qty 4, 1-ohm resistors in series with some 1 ohms resistors in parallel to make up the fractions of an ohm required to balance the divider.For a permanent installation into a cabinet, I think I will borrow a Fluke configuration that is used in their 732B 10V reference. They have small PCB rotary switches that have fixed resistors. You can call it a PCB mounted decade box. You can insert a screwdriver increase or decrease the decade of resistance that you want to dial-in. It is a very clever idea. No more noisy potentiometer wipers.I have to go find a suitable PCB switch for this purpose. The other option is to mount some surplus KVD or deacde box switches on the front panel and use those.

author: JS
author_rank: Frequent Contributor
timestamp: October 04, 2016, 11:22:21 pm
content: Quote from: VintageNut on September 29, 2016, 09:20:00 pmNice approach, why not 1234 configuration decade resistors? with a 16 pdip switch package and 8 resistors you'd have 2 full decades, with times 2 resistors you could avoid having twice the same value and have an 8bit (non volatile) programable resistor, which for what you are telling should be enough to do the job. I guess you are using el cheapo resistors for this as the stability wouldn't matter much for those...I've have a 32bit converter coming and I'm trying to figure out how to do a decent decade divider, even buying a nice vishay (assuming I can get one to arrive here) would be a pain to characterize, I could have access to a decent lab at the university but not for too much time, I could get a few references from them to say. I could bring my voltage reference and a few resistors and them tell me the value for a reference temperature, then I would have to find the way around.JS

author: VintageNut
author_rank: Frequent Contributor
timestamp: October 05, 2016, 06:27:33 pm
content: Yes el-cheapo resistors for trimming. The trim is less than 1 ohm which is 100 ppm of 10kohms. So, 100 ppm drift of the 1 ohm should not show up in the actual division ratio. that is my assertion. Fact may be different.The Vishay Z-Foil family is essentially zero TC at some temperature. Have a look at the datasheet. The price is not for the el-cheapo crowd. The S-family is similarly almost zero TC at some temperature near 25C.As an update, I trimmed the string for nearly 10:1 compared to my Fluke 731B. I let the string sit out in the open air in my office that is open to the entire 1st floor of my house at 1000 ft^2. The temperature in my office is not anything approaching lab-grade stable.The string ratio has a meandering drift of about +/- 3ppm to +/- 4ppm. This is just eyeballing the DMM monitoring the bottom 10K resistor throughout several days. My theory is that if the string was immersed in oil and in a proper enclosure, the stability might be good enough for 1 or 2 ppm of uncertainty which is better than most 6 1/2 digit DMMs if you look at the datasheet.So, I may go ahead and find the proper enclosure and oil tank for this collection of resistors and see how the project develops.I did pull the trigger on buying some better quality modern-day resistors to try to make a Hamon string that may also be configurable as a cascade string. I also bought a few extra to make a proper bridge for performing the Hamon trick and for having a try at the cascade string bridge.

author: VintageNut
author_rank: Frequent Contributor
timestamp: October 06, 2016, 01:36:20 am
content: Quote from: JS on October 04, 2016, 11:22:21 pmI took a look at a couple of binary resistance box projects. Nice idea. I think that I want to go from 0.01 ohms to 1.0 ohms. So, I will need 0.01, 0.02, 0.04, 0.08, 0.16. 0.32, 0.64. The very low resistance values are probably going to be hand wound wire around a large value resistor. Adding a 0.005 to the bottom fills out the8 positions and gives a finer granularity. This "pot" would span 0.005 ohms to 1.275 ohms with a resolution of 0.005 ohms.I made a 0.01 ohm resistor recently just to do it. It was a fairly short piece of insulated solid copper wire twisted to minimize inductance and shoved into to banana plugs which allows using a DMM force and sense plugs to tweak it. I used it to look at voltage burden of various ranges of a Sourcemeter.I think that the latest greatest vishay resistors with guaranteed low tempco in a shielded box will probably suffice for a good divider to check your converter. Give it a try and see.

author: VintageNut
author_rank: Frequent Contributor
timestamp: October 22, 2016, 02:23:23 pm
content: Quote from: DiligentMinds.com on September 26, 2016, 03:27:37 amThis idea, I believe, is the winner.After some weeks of researching the Datron 4902(S) and the Measurements International 8000B and the articles from the developers of the MI8000B, it looks to me that a mixture of these approaches may be very good for a DIY divider that can be used to rival the performance of the Fluke 752A and the 720A for use in a DIY home lab for precision divided voltages.A stack of nominally accurate resistors that can be calibrated quickly and accurately every time the divider is used seems to me to be the most practical implementation.Adjustment pots in the Datron 4902S and the switches in the MI8000B are the sources of difficulty and error.What I do like is the procedure to perform an automated measurement of each element of the resistor stack before and after every use of the divider.Here is what I am thinking of building1. A 3-decade resistor stack. 10 pcs of 1K + 9 pcs of 10K + 9 pcs of 100k. No switches and no pots. Every step of every decade is brought out to a binding post for use as a calibrated voltage for a null meter connection. The top of the stack will be nomianally 1M ohm and calibrated at 1000V. So the voltages will span 1000V to 1V with 28 total cardinal points.2. System for automated measurement of every position of every decade. This will be a Keithley DMM that accepts switch cards or a Keithley 7001 switch system. I own each and will have to find the correct switch cards to perform the switching and measurements. It will depend on the cost of the cards.3. voltage sources for energizing the divider and for comparing the decade steps. Fluke 731B for the 10V and 1V step comparison voltages. Maybe the Fluke 332A for the 100V step comparison voltage. For divider energizing, maybe a Keithley 237. The model 237 can force current or can force voltage up to 1000VDC.The idea is to use what I have in my lab now except for acquiring the correct switch cards.This is all just paper design right now. Any suggestions are welcomed.

author: cellularmitosis
author_rank: Unknown
timestamp: May 30, 2018, 02:37:39 pm
content: Hi vintagenut, and progress on this idea?

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 06, 2019, 02:20:04 pm
content: Quote from: VintageNut on October 22, 2016, 02:23:23 pmDo you have any information about the 8000B internals?