Fluke 332A adjustment/verification - Page 1
Forum section: electronics / testgear

author: VintageNut
author_rank: Frequent Contributor
timestamp: May 29, 2015, 11:49:15 pm
content: Bought a 332A for keeping a DC standard in my lab. I have use of a Keithley 2002 that is within its one year cal date.Slid back the cover enough to expose the adjustments. The inner case is a guard and is at the output potential. 1000V at 50mA is potentially lethal. Placed straws in the adjustment holes. Covered the screwdriver blade in shrink wrap for double insulation.First check is for zero volts on all three ranges 10V, 1000V and 1000V.10V range error less than1 ppm100V range error less than 1ppm1000V range error less than 1 ppm.No zero adjustment required.A full-scale check shows 10V range in spec. 1000V range 35 ppm off which is over spec. So, if one range needs adjusted, then they all get the treatment.Next, set each range for full scale and adjust pots for as close to a full scale reading on the 2002 as possible. The 10V range and 100V range have good resolution turning the pot, single ppm changes are fairly easy. On the 1000V range, any change is going to cause 5ppm movement. It would be a good design change to add another fine tune pot to the circuit.Once that was finished, I ran through the linearity test with 1.111111, 2.222222, .... 9.999999 on all three ranges. 30+ pictures, just a few here:444.4444V error less than 8ppm77.77777V error less than 4ppmThe only stinkers in the bunch are 11.11111V and 1.111111V11.11111V error is 29 ppm. Spec is 32 ppm so no cause for concern but all of the other errors are much less. I am thinking that a string adjustment may fix this but there are no directions for a string adjustment.1.111111V error is 13ppm. Not bad but larger than almost all of the other errors.Another test is all 9's. These should be very nearly the same as full scale readings.999.9999V error is 1ppm Nice!99.99999V error is 2 ppm9.999999V error is 6ppmLest anyone that this is a quick process, it is not. The instrument needs hours to warm up. Measurements take minutes to settle. DMM is set to 10NPLC with 10 length filter. This is pretty much an all day effort.Now the instrument is closed and back in the equipment rack. Re-check full scale readings.1000.0000V less than 2ppm error100.0000V less than 2ppm error10.00000V less than 2ppm errorThis was a fun project. If anyone has a procedure for adjusting the string I would appreciate having a copy.

author: dacman
author_rank: Frequent Contributor
timestamp: May 30, 2015, 01:46:31 am
content: I would suggest testing all the electrolytic capacitors. If you have an LCR meter that uses a bridge circuit, it will give accurate enough results in-circuit at the values of the larger capacitors (i.e., the electrolytics).For a sample string adjustment procedure, go towww.fluke.comand search for the 332A.

author: VintageNut
author_rank: Frequent Contributor
timestamp: May 31, 2015, 08:02:09 pm
content: Success with string adjustment. Had to print out the string schematic, piece it together and go through it slowly. Read and re-read the US Army instructions. Concluded that it can be done with a DMM.The schematic is here. It is fuzzy (non-steady hands) but the original is free to download from Fluke even to this day 50 years later. If someone has a paper original I would appreciate a high rez scan.Here is my procedure:1. Set range for 1000V.2. Set decade 1 for 10, all other decades set to 0.3. Set output on4. Adjust 1000V range pot for as close to 1000.000 as possible. This pot is difficult to make any better than +/- 5 ppm on my 332A.5. Set output off6. Set decade 1 for 1. All other decades are 0.7. Adjust pot R901 for a reading of 100.0000.9. Change the first decade dial to 2. Adjust pot R902 for a reading of 200.0000. This may cause full scale voltage to be over/under 1000.000. Re-adjust 1000V calibration pot for an output of 1000.000 with first decade dial at 10. Full scale output is the addition of settings 2, 4, 6, 8 and 10 resistors. Adjusting any of the even decade dial setting pots will change the full-scale output.10. Repeat step 9 until 200V and 1000V are as close to perfect as possible.11. Set first decade dial to 3. Check that output is 300.0000. You cannot adjust this output. The output is the sum of the 100V setting and the 200V setting.12. The dial 1 position and dial 2 position are the foundation of all of the rest of the settings of this decade. You may want to start at the beginning and go over all of the steps to insure that 100.0000V, 200.0000V and 1000.000V are all as close to perfect as you can make them.13. Change the first decade dial to 4. Adjust pot R904 for a reading of 400.0000. This may cause full scale voltage to be over/under 1000.000V. Re-adjust 1000V calibration pot for an output of 1000.000 with first decade dial at 10. Full scale output is the addition of settings 2, 4, 6, 8 and 10 resistors. . Adjusting any of the even decade dial setting pots will change the full-scale output.Continue through the first decade pot adjustments until you finish up at 1000.000V.Verify that you have outputs of 100.0000, 200.0000, 300.0000, 400.0000, 500.0000, 600.0000, 700.0000, 800.0000, 900.0000 and 1000.000 for the dial setting 1 through 10 of the first decade dial.Move on to the second decade dial. Set the first decade to 0 and decades 3 through 7 to zero as well. Use the same process as above to set output voltages of 10.00000, 20.00000, 30.00000, 40.00000, 50.00000, 60.00000, 70.00000, 80.00000, 90.00000 and 100.00000. You will NOT be adjusting the range calibration pots in these steps.All of the settings of all of the dials of my 332A are proportional and result in less than 10ppm error. For the first 6 digits, the output is exactly what you set it to. The 7th digit is set to zero and the reading on the DMM for the seventh digit is the uncertainty. ppm error is the 7th digit reading divided by the 332A setting.Here are two examples1098.76V, The 0.001 volt digit is the uncertainty. About 7 ppm here123.456V The 0.0001 volt digit is the ppm error. About 1 ppm hereThe 7th digit of the 2002 is stable for this cabling setup. Digits 8 and 9 are pretty much noise.This process required a bit over two hours to accomplish not including instrument warm up. The 332A seems to require at least two hours to warm up. Very good stability after four hours.

author: dacman
author_rank: Frequent Contributor
timestamp: June 01, 2015, 02:14:12 am
content: Why didn't you use the procedure in the Fluke manual page 3-2? It uses the 3rd dial as a reference and steps up from there.

author: TiN
author_rank: Super Contributor
timestamp: June 01, 2015, 04:53:02 am
content: Thanks for posting, enjoy your standard! Also would suggest keeping cover closed for tests, as it may upset temperature compensation of internal parts.Shipping cost of such beasts make them pretty unaccessible for me :

author: VintageNut
author_rank: Frequent Contributor
timestamp: June 01, 2015, 08:38:25 pm
content: Quote from: dacman on June 01, 2015, 02:14:12 amGood question. 00X.0000 on the 1000V range yields 10V. Measured on the 10V range of the 2002 shows 13 ppm high.

author: VintageNut
author_rank: Frequent Contributor
timestamp: June 01, 2015, 08:41:31 pm
content: Quote from: TiN on June 01, 2015, 04:53:02 amIt was located in the next state north so the shipping time was just two days. It was open only for adjustments. In fact I got tired of closing and opening it so today I cut slots to allow adjustments with the case closed. Now I just have to make a cover for the slots.

author: VintageNut
author_rank: Frequent Contributor
timestamp: June 01, 2015, 11:39:18 pm
content: I was curious to see if I could find an indication of data of manufacture. So, off came the inside cover for some peeking and poking. Voila! There is a date code on the high voltage transformer.February 1967! Wow. 48 years young!A look at the high precision resistance string with adjustment pots for the first two decades.Current reference assemblyExtractable cards in card cage slots

author: PaulAm
author_rank: Frequent Contributor
timestamp: June 02, 2015, 12:16:10 am
content: I see you have the extender card as well. That was a nice touch by Fluke.I picked up a 332b marked as "for parts or repair" for cheap, and the only thing wrong was operator error - they had the voltage trip control turned all the way counterclockwise. To be fair, I also had to replace a couple indicator lights.Shipping can be horrible, but I bought mine from a surplus dealer who does a lot of shipping so it wasn't too bad. I think it was around $50 US.Now I'm looking for a Keithley 2001 that I can repair and get calibrated for a reasonable sum so I have something to check it with. Or maybe I should just mask off the last 4 digits

author: gilbenl
author_rank: Regular Contributor
timestamp: June 02, 2015, 12:24:12 am
content: Very nice! Do you mind sharing how much you paid for it?

author: VintageNut
author_rank: Frequent Contributor
timestamp: June 02, 2015, 12:43:10 am
content: Quote from: gilbenl on June 02, 2015, 12:24:12 am$300 including shipping.

author: Vgkid
author_rank: Super Contributor
timestamp: June 02, 2015, 12:54:37 am
content: What a beautiful piece of gear.

author: VintageNut
author_rank: Frequent Contributor
timestamp: June 02, 2015, 12:57:16 am
content: Quote from: PaulAm on June 02, 2015, 12:16:10 amThat is cool that you scored a 332B that only needed a knob turned to get it to operate properly. I would prefer the 332B as it has a trap door to perform adjustments from what I have read.An interesting outcome from this exercise is that my 2000 DMM DCV measurements are very close to the 2002. My 2000 has had 8 calibrations so my conclusion is that the 2000 has been aged properly and is probably not going to drift significantly until it dies some day. Measuring 10V, the two DMMs are within less than 5 ppm. They diverge more at 1000V.I bought a 2001 fixer-upper with the idea that it would be my standard when I return the 2002 loaner. Now that I have used the 2000 beside the 2002, I am going to use the 2000 as my bench DCV reference.If you want to discuss purchasing my 2001 fixer-upper, you can send me a pm.

author: dacman
author_rank: Frequent Contributor
timestamp: June 02, 2015, 02:10:52 am
content: When adjusting the sample string (using the Fluke manual) it doesn't matter that the 3SD, set to X, is 13 PPM off. (This offset is removed later.) After the sample string is adjusted, the dials above it will also be 13 PPM off (being referenced to the 3SD), and when the ranges are adjusted at the end, the 3SD, set to X, should then be nominal.

author: VintageNut
author_rank: Frequent Contributor
timestamp: June 02, 2015, 03:54:46 am
content: Ok. Thanks for the explanation. I will have to read the procedure more carefully and give it a try.

author: Dr. Frank
author_rank: Super Contributor
timestamp: June 02, 2015, 07:10:29 am
content: Quote from: VintageNut on June 02, 2015, 03:54:46 amHi, and congratulations on that nice calibrator.Does it have the mechanical chopper?And does that still work properly?Anyhow, you have to linearize the sample string first, starting comparing Deck C vs. Deck B: 00x0000 <=> 0100000 and working upwards.After that, the 10, 100 and 1000V ranges may be calibrated.The other way round, you will fail!I recommend another army document, for the 332B/AF, from 1972, better quality , especially the schematics, which fully covers your instrument (332A),butalsoincludes the newer versions, with the MOSFET chopper, and the more precise sample string, where DECK C can also be adjusted.I recommend also to get the 332D, 1975 document, where Fluke improved the linearization process.They compare consecutive steps on 1.. 10V voltage levels, instead of 10..100V, which is much more precise, especially if you use a DMM.In your 332A case, you would use the 100V range only for the DECK B linearization, and 10V range for the DECK A linearization.Both documents have around 20MB of size, so I can't upload it here.Send me a PM, if you'd like to get these.FrankFurther remarks:- Linearization at max. 10V level also is more safe, as the inner shield will not rise to more than about 40V.- The linearization process requires about 0.1ppm resolution and/or linearity of the DMM used.If you still have access to the 8 1/2 digits Keithley, then it's fine, and you may also adjust the sample string easier, by directly adjusting 00x.00 => 010.00, 01.000, 02.000, 04.000, 06.000, and so forth, instead of comparing two settings like 01.X00 vs. 02.000 and so on.That's described in the 332D/1972 manual, which uses a 720A KV for linearization.Latter instrument is specified for 0.1ppm linearity, and would be replaced by the 8 1/2 digit DMM.- If you have a 6 1/2 digit DMM only, then the linearization is not possible to the required accuracy..

author: VintageNut
author_rank: Frequent Contributor
timestamp: June 02, 2015, 10:02:15 pm
content: Hello Dr. FrankI believe that I have those documents. It is a bit confusing since I am not using a divider nor a null meter. I have read the documents over and over and tried to perform the steps. I am always left with 20 ppm to 30ppm error with dials set to 00X.0000. I have performed the procedure at least 4 times.I surmise that I want 00X.0000 to be exactly 10.0000000 volts on the 2002. So I set the 332A range to 1000V and the dials to 00X.0000. The reading on the 2002 is over 20 ppm high. I adjusted the 1000V calibration control so that the 2002 reads 10.0000000V. Then I moved the 332 dials to 010.000000 and adjusted R907 for 10.0000000V on the 2002.Regularly I go back and check 0X0.0000 and adjust the 1000V range calibration control for 10.0000000V if it has moved.I worked my way up the dial settings and have all of the readings +/- 1ppm for most and +/-2 ppm for a few of the highest dial settings .I think this is how it should be done with a DMM. Let me know if you disagree.I do not know if it has a mechanical chopper. The serial number is 845 and the date on the transformer is 1967. I do not hear any noise. I have a Keihtley 147 with a mechanical chopper and it can be heard everywhere in the house.Whatever chopper is used, it is noisy electrically. There is 3-5 ppm noise on most settings.

author: Dr. Frank
author_rank: Super Contributor
timestamp: June 02, 2015, 10:32:46 pm
content: Hi,I quite don't understand your approach, or maybe, I understand your 'thought error':The linearity adjustment only compares one resistor (or let's say better, the foregoing two of them) to the next one, (with double the value).These were made equal to about 0.5ppm.If you proceed further, you end up with a linearity of Deck A and B of about these 0.5ppm offull scale! (Comparable to any modern 6 1/2 digit DMM!!)If you then adjust the different ranges, i.e, 10V, 100V and 1000V on full scale, i.e at X000000 settings, this can be done to a few ppm absolute accuracy, initially.If you output 10V on the 1000V range, the above described linearity really has to be calculated as 0.5ppm (linearity error) of 1000V.You can't do better than that!!0.5ppm of 1000V are 500µV.500µV of 10V are 50ppm error!Hey, that's 1% of F.S. reading! That's normal!!Therefore 20ppm are very good, and easily explained:Always use an instrument on the highest possible setting / readout!Therefore, for 10V output, use the 10V range, that'll be a few ppm only!For the chopper: I think, that's inside the double metal box.. see pictures of the A version..And it's really a wonder, that it's still working..These mechanical choppers are the first to fail inside these instruments..The noise is relatively normal, especially, maybe, with a mechanical chopper.I think I have published noise measurements of my former 332B/AF, having this MOSFET chopper already (I gave it away to Australia, into another 332A).Please search for "332B .. in the slaughterhouse"Frank

author: guido
author_rank: Regular Contributor
timestamp: June 02, 2015, 10:35:31 pm
content: You could put in a modern chopper replacement. See here:http://friedrich-messtechnik.de/index.php/bauanleitungen/87-...uke335-332I did in a 335D:Guess where the connectors on the new pcb came fromQuote from: VintageNut on June 01, 2015, 08:41:31 pmA standard feature of the 335D; there is a panel you can remove to access the adjustments. There is pcb material without copper to shield off the inner casing (which could sit at 11kV). Guess there were more complaints.Quote from: PaulAm on June 02, 2015, 12:16:10 amIn mine somebody exchanged the main filtercaps. And then switched both fuses at the back. Which resulted in one blown fuse at power on. Easy fixBut it was missing a transformer in the null meter section. Despite the fact that i could source it in the US (somebody with a 335 slaughterhause), the null meter still doesn't work (yet).There was no extender card, so i had to make one myself.

author: fmaimon
author_rank: Unknown
timestamp: June 02, 2015, 11:51:08 pm
content: Quote from: Dr. Frank on June 02, 2015, 07:10:29 amWhy? If you use an 6 1/2 DMM with relative mode (8846A, 34401A, etc), you just need to check if every pair of resistors (1, 2, 4 and 8 group) has the same ratio. You should get a good match doing that.

author: VintageNut
author_rank: Frequent Contributor
timestamp: June 03, 2015, 12:54:58 am
content: Quote from: Dr. Frank on June 02, 2015, 10:32:46 pmHi Dr. FrankI tried the lower voltage range first and gave up on it. Here is why. The floor is not zero. If you look at the spec, the noise floor (and/or zero offset) on the 100V range can be as much as 20 uV. If you are outputting 1V on the 100V range, 20V of zero offset is 20 ppm error.The zero offset on the 1000V range is 40 uV maximum which is 4ppm error.I was able to get all three ranges adjusted below 10uV zero offset. That is still 10 ppm offset at 1V on the 100V range. The initial step in the entire process is to measure 00X.0000 and compare it to 010.0000. I could never get rid of the 10 ppm offset. So, I used the 1000V range where the offset is the lowest ppm. I adjust the 1000V calibration pot to get exactly 10V on the 2002. Now the third decade is exactly correct and the higher decades use the third decade as the reference.

author: dacman
author_rank: Frequent Contributor
timestamp: June 03, 2015, 02:01:42 am
content: How are the aluminum electrolytic capacitors? I've replaced lots of them in 332A/B/D and 335D units. I'd test them all. Also, the chopper is critical for stability.

author: nukie
author_rank: Frequent Contributor
timestamp: June 03, 2015, 02:36:14 am
content: Ah ha some discussion about these heavy beasts. I have a 335A and most of the electrolytic caps on the sub boards are toss. I replaced most of them they are getting harder to source. I looked at the main caps at the back covered in cardboard sleeves those are monsters don't know where to find them.Finally, my relay died one day, I replaced it with a similar coil wattage. I'm surprised the original relay manufacturer is still around and the same model is still being made!!

author: VintageNut
author_rank: Frequent Contributor
timestamp: June 03, 2015, 03:19:01 am
content: Quote from: dacman on June 03, 2015, 02:01:42 amGood question about the caps. I have no idea unless I take the boards out and test. That will probably be a winter project. Good idea about checking out the chopper. If that is not stable that would explain some behaviors I am seeing.Nobody has brought up the pots. At least two of the string pots are dirty/worn. The output makes unexpected jumps while adjusting or the output goes down while you are adjusting up. It would probably make sense to replace all of the pots.

author: Dr. Frank
author_rank: Super Contributor
timestamp: June 03, 2015, 07:45:36 am
content: Quote from: VintageNut on June 03, 2015, 12:54:58 amHi VintageNut,It's necessary first to separate the parameters zero offset, noise and absolute error.See 332A-1965 manual, page 1-1, and also the calibration description also.The zero offset is specified inside the Calibration Accuracy:10µV for 10V range,20µV for 100V range,40µV for 1000V rangeYou'll find these values also in the description of the zero offset calibration on page 3-1noise is specified separately, on page 1-1, 20/30/40µV rms for these three ranges, accordingly.absolute accuracy is 30ppm for each range, plus the zero offset error.Linearity error is not specified, but may be estimated to about 0.5ppm for the sample string, following its calibration procedure, and can be ignored in first order.The zero offset on the order of 10µV that you mentioned, should be relatively constant, therefore a comparison of two equal values like 002.x000 V vs. 003.0000 V should be possible to 1µV stability / accuracy, as described in the 332D-1972 manual.In other word, this constant offset does not affect this adjustment process.But you did it right, using 10V for equalizing 3rd vs 2nd decade, because that is more stable.The high noise level of the mechanical chopper on the order of 20..40µV has to be averaged out by a longer time constant of the DMM, (something like NPLC 200, or longer) to again achieve < 1µV accuracy. That may be a bigger problem, as this slows down the adjustment process.Things would be a bit better with the MOSFET chopper.Zero offset is < 2µV on all ranges, and short term noise may be as low as 4µV rms, see my measurements here:https://www.eevblog.com/forum/testgear/fluke-332baf-in-the-slaughterhouse/msg399310/#msg399310In the end, I think you succeeded in adjusting your 332A, as far I understand your comment?Frank

author: Dr. Frank
author_rank: Super Contributor
timestamp: June 03, 2015, 08:24:57 am
content: Quote from: fmaimon on June 02, 2015, 11:51:08 pmNo, that's not true!You are about a factor of 10 short in resolution and linearity, if you take a close look at the adjustment requirements.Using a DMM, you have to follow the adjustment procedure in the 332D-1972 manual, page 4-12, and to adapt that to the different sample string design of the A version.Therefore, you have to adjust voltages of 1, 2, 4, 6, 8 and 10V to 1µV accuracy (equals the 845AR null requirement).You need to use a fixed 10V range on the DMM for that, but the resolution is 10µV for a 6 1/2 digit instrument only, that's exactly that factor of 10 too insensitive.Also the linearity is 1..2ppm of 10V range only, so you get an additional 10..20µV error.Even the new 34470A would not be capable to do this adjustment, as it has the necessary resolution, but its 1.5ppm non linearity also kills the game for absolute voltage measurements.You may only use the initial linearity adjustment procedure on page 4-10, which needs a relative measurement with 1µV resolution only, (in contrast to absolute measurement). But this does not give full accuracy, obviously.What do you think, why this linearity adjustment requires the ultra linear Fluke 720A Kelvin Varley divider, which is specified for 0.1ppm non linearity??The other possibility would be a (Wheatstone) Bridge, with 0.1ppm zero resolution and stability .. which is implemented inside the 720A, so that this instrument can be self-calibrated to that extreme linearity.The 720A KV can be replaced only by a few 8 1/2 digit DMMs, maybe the Keithley 2002, just closely by the Fluke 8508A, but for sure by the HP3458A, which is nearly an order of magnitude more linear.Frank

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: June 03, 2015, 06:19:52 pm
content: Anyone know the differences in performance/specs on 341A versus the 332A, and the vintages, desirability, etc.

author: VintageNut
author_rank: Frequent Contributor
timestamp: June 03, 2015, 10:13:26 pm
content: Noise is a big problem as is the zero offset. That said, the attached is what I have accomplished. I have net edited for correctness of pot designators and some the pictures are fuzzy. I will make a good copy eventually.

author: VintageNut
author_rank: Frequent Contributor
timestamp: June 03, 2015, 11:57:07 pm
content: Quote from: SoundTech-LG on June 03, 2015, 06:19:52 pmThe datasheets are on Fluke's web site. The 341A has a basic uncertainty of 100 ppm. The 332A is 30 ppm. The 341A appears to be a smaller sized and less accurate model. It was probably substantially less cost.

author: VintageNut
author_rank: Frequent Contributor
timestamp: June 04, 2015, 04:15:04 am
content: Hello Dr. FrankThe uncertainty in linearity of the Keithley 2002 is 0.1 ppm typical and 0.2 ppm max. It seems to be the same as the HP 3458A although I they only give a number without stating typical/min/max.The Keithley 2000 only gives linearity on the 10V range and it is 1 ppm. My 2000 and the borrowed 2002 agree very closely on the 10V range but not on the higher ranges. I will post some pictures of that soon.

author: Dr. Frank
author_rank: Super Contributor
timestamp: June 04, 2015, 06:22:50 am
content: Quote from: SoundTech-LG on June 03, 2015, 06:19:52 pmWell, yes..The 341A/343A was designed around 1969, see manual.The 343A is preferred over the 341A, as it has 7 digit resolution and is more stable and more precise, i.e. 50ppm of range for the 341A, 20ppm for the 343A.The later 332D/335D and the 332B / 332B/AF versions have 10ppm and 20ppm of range.The 341A/343A circuit is similar to the 332/335.Its high voltage stage is much easier, by simply switching the transformer windings in 100V steps, instead of that bulky, heavy and sometimes unreliable switch mode preregulator inside the 332/335.The 341/343 already has a fully transistorized chopper amp, and a sample string, which is very similar to the 332/335.The reference is not ovenized, giving a bit less of stability, 15ppm/month compared to 5ppm/month for the 332/335. Warmup time is much faster, only 1/2h, compared to 2..4h at least for the 332/335.The 341/343A is lightweight (23pounds vs. 50pounds), compact, and a nicely built unit.If you go for the 332/335 instead, the A and B versions have the mechanical chopper, a less stable simple zener diode reference, and less accurate sample string.Therefore, the 332 B/AF and 332/335D versions are highly recommended.Frank

author: Dr. Frank
author_rank: Super Contributor
timestamp: June 04, 2015, 07:39:29 am
content: Quote from: VintageNut on June 03, 2015, 10:13:26 pmWell, sorry to say, but you have really made a faulty linearity calibration on your 332A!At first, you simply do not follow any of the described adjustment procedures, neither of the 332A, nor the 332D.The first error is, that you don't compare the 3rd decade to the 2nd correctly, i.e. the direct transfer 00x.0000 V => 010.0000 V by adjustment of R907 is replaced by the much less precise 00x.0000 V=> 01X.0000 V comparison.At that point, the zero offset contributes an additional error.That would be not the case, if you would compare equal 10V voltages, as intended!Then the biggest fault is, that you don't do the further comparisons on the fixed 10V range of the 2002, (1,2,4,6,8,10V sequence for each deck B and deck A) and thereby NOT using its 0.1ppm linearity/transfer accuracy.Instead, you change the range on the 2002 twice, i.e to 100V and 1000V!The accuracy of these ranges is at least worse than 5 ppm , so the linearity of the 332A is faulty by that accuracy error, cumulatively.That is a factor of about 100 worse than required!Why don't you simply follow the calibration manual of the 332A, or the adapted 332D, as explained?And yes, please, you should delete your erroneous 'calibration' procedure from the net!Frank

author: dacman
author_rank: Frequent Contributor
timestamp: June 05, 2015, 12:22:45 am
content: Quote from: VintageNut on June 03, 2015, 03:19:01 amI use Bourns 3009P series for replacement trimmers, but if I cannot find the correct value I will then get either a Bourns 3006P or Vishay 043P (both of which are a little short) and stand them off with a piece of tie strap that I cut to fit. (I punch holes in the tie strap for the trimmer leads with a scribe.)

author: VintageNut
author_rank: Frequent Contributor
timestamp: June 05, 2015, 02:50:01 am
content: Hello Dr. FrankThank you for the words of wisdom. You are absolutely correct. I was doing it wrong. I went through the procedure again using only the 20V range of the Keithley 2002. It worked very well. The only tricky part is 010.0000 on the 332A's 100V range is 1V out. Measuring 1V on the 2002 on the 20V range drops the first significant digit.I will delete the earlier document and take some new pictures and post that.The 332A now agrees extremely close to the 2002's 20V range. The 332A now shows the deviation of the 2002's 200V range and 1000V range. I will get pictures of that as well.Thanks again, Dr. Frank.

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: June 05, 2015, 05:45:10 pm
content: Quote from: Dr. Frank on June 04, 2015, 06:22:50 amWell thank you for your quite well informed reply. I have had the 341A for many years, had to do some repairs months ago, but it seems to be very stable, and accurate, and plenty good enough for even the most demanding level of accuracy I would ever need, and the price was right, so it works for me. I was confused on the production years of those models, and did not know the 332/335 was so heavy. So it is good to know. Once again I appreciate all the information.