DIY 34401A calibration - Page 1
Forum section: electronics / testgear

author: baoshi
author_rank: Regular Contributor
timestamp: January 27, 2015, 04:33:38 pm
content: Does anyone know, how is the internal wiring of Agilent's 34172A/B short block ?I have made this but many tell me it is not the correct way for 4 wire short.ThanksSent from my iPhone using Tapatalk

author: Zucca
author_rank: Unknown
timestamp: January 27, 2015, 04:53:56 pm
content: Quote from: baoshi on January 27, 2015, 04:33:38 pmWhy? It should be fine, I would have done it differently anyway. Sense wires carry low current, no need of big copper there.

author: jlmoon
author_rank: Unknown
timestamp: January 27, 2015, 05:13:05 pm
content: That would be an industrial strength shorting block. indeed.

author: jpb
author_rank: Super Contributor
timestamp: January 27, 2015, 05:25:14 pm
content: For my Keithley I use two separate standard two pin shorts (see attached photo) which I connect by thick copper wire, it seems to work ok. Doing it with 4 pins as you've done should be fine - the only thing is that you need to be more accurate on placing to avoid perhaps mechanically putting strain on the sockets and I wouldn't trust my own metal working skills to do this - but you look to have done a good job.NB I put the shorts across force and across sense so the copper wire shouldn't carry any significant current so any contact resistance effects should be negligible.

author: macboy
author_rank: Super Contributor
timestamp: January 27, 2015, 06:12:15 pm
content: Quote from: jpb on January 27, 2015, 05:25:14 pmIt isn't contact resistance that you need to avoid, it is thermoelectric potentials. With all those plated metal surfaces, that is a lot of possible thermocouples. With the right (wrong?) combination of metals, even a fraction of a degree difference can result in microvolts of offset. This is an issue when calibrating null on a 6.5+ digit meter.Keithley's shorting block is built on a PCB like attached.I think the solid copper block is a good idea. I would prefer a plastic standoff instead of a heat-conducting copper screw.

author: jpb
author_rank: Super Contributor
timestamp: January 27, 2015, 07:00:21 pm
content: Quote from: macboy on January 27, 2015, 06:12:15 pmI'm no expert, but I'd be surprised if it was a problem for 6.5 digits. I used the approach for the self test on the Keithley which it passed happily so presumably any effect was within the allowed spec.Out of interest I just experimented a bit with different combinations of connecting the short both directly and via a copper wire between two shorts and with every combination my meter was reading somewhere between 3.3 and 3.8 microVolts (Edit : this drops to around 0.4 microVolts on warming up) which I think is just noise rather than thermo-couple effects.I accept that you have to be rather more careful with 7.5 and 8.5 digit meters.

author: quarks
author_rank: Frequent Contributor
timestamp: January 27, 2015, 07:07:57 pm
content: probably this is interesting for you to readhttps://www.eevblog.com/forum/testgear/lking-for-gold-plated-tellurium-copper-banana-plugs/msg246371/#msg246371

author: Dr. Frank
author_rank: Super Contributor
timestamp: January 27, 2015, 10:50:08 pm
content: baoshi,your short is just perfect!The big copper plates takes care for low resistance < 1mOhm between hi and lo, and it also takes care for minimum temperature differences between all four plugs, due to its low thermal resistance. This mitigates possible thermal voltages. Also, each plug only has one relevant contact point to the base plate - underneath.If you wait several minutes after application, you will measure no thermal offset at all.Look there, that simply bent copper wire is how the 3458A should be shorted, as it's officially drawn in the calibration manual.That is good for <10nV offset calibration for 8 1/2 digits DCV, and for 7 1/2 digits low ohm (<1mOhm) so that mainly the internal front/rear switch and internal PCB connections can be zeroed during calibration (the 34401A is very similar concerning the front end).For the 34401A, I soldered that clumsy short on the right, accordingly.But your design is much better, because it is more simple, and elegantly designed.Frank

author: LaurentR
author_rank: Frequent Contributor
timestamp: January 28, 2015, 12:56:21 am
content: http://us.flukecal.com/products/accessories/test-leads-probes-and-clips/884x-short$30 - a tad bit cheaper than the $200 Agilent shorting blockOr stack three Pomona 2035 (or two 2035 and one or two 3030) - ~$7 eachhttp://www.pomonaelectronics.com/pdf/d2035_100.pdfhttp://www.pomonaelectronics.com/pdf/d3030_1_01.pdf

author: Vgkid
author_rank: Super Contributor
timestamp: January 28, 2015, 01:07:54 am
content: Dr. Frank, who made those bananna plugs?

author: baoshi
author_rank: Regular Contributor
timestamp: January 28, 2015, 01:26:36 am
content: Quote from: Vgkid on January 28, 2015, 01:07:54 amIf you have access to taobao.com here is a linkhttp://item.taobao.com/item.htm?spm=a1z09.2.9.63.ewdDg2&id=22233300725&_u=s15rvgic7df

author: baoshi
author_rank: Regular Contributor
timestamp: January 28, 2015, 01:27:17 am
content: Thanks everyone.My idea is the link between the "force" terminals (left) and "sense" terminals (right) need not see current flow. So the connection should be thin. Something like below. Apparently the 3458A calibration manual suggests the same layout.

author: baoshi
author_rank: Regular Contributor
timestamp: January 28, 2015, 03:36:17 am
content: Quote from: joeqsmith on January 28, 2015, 01:53:15 amAfraid not. See no point to automate it. Just picked up a 34401a and some 9-output reference categorized by a 8.5. Trying to calibrate it.Sent from my iPhone using Tapatalk

author: Dr. Frank
author_rank: Super Contributor
timestamp: January 28, 2015, 07:47:37 am
content: Quote from: Vgkid on January 28, 2015, 01:07:54 amThat's stuff from mc, multi-contact.afaik, it's a copper beryllium bronze, gold, hard plated. LS4 + KT4-BFrank

author: HighVoltage
author_rank: Super Contributor
timestamp: January 28, 2015, 09:42:17 am
content: Your copper plate seems perfect.I wanted to do the same, but never got to it.The 4mm studs are made by MC (Multi Contact) and I got them already.So far I have used MC gold plated banana plugs and soldered heavy copper wires on to them, similar to the version by Dr.FrankIt works perfectly.

author: TiN
author_rank: Super Contributor
timestamp: January 28, 2015, 11:31:54 am
content: Not 100% relevant, but since we talking about shorts, I have some PCBs with various shorting configurations.Fluke have note advisingagainst big thermal mass shorts

author: HighVoltage
author_rank: Super Contributor
timestamp: January 28, 2015, 12:36:25 pm
content: Quote from: TiN on January 28, 2015, 11:31:54 amHello TiNYour link to the Fluke document is not workingCould you please fix that.

author: baoshi
author_rank: Regular Contributor
timestamp: January 28, 2015, 05:09:43 pm
content: Is this the article TiN has mentioned?http://us.flukecal.com/literature/electrical-calibration/watch-out-those-thermoelectric-voltages-cal-lab-journal-reprintI start to buy in the theory.

author: radioFlash
author_rank: Regular Contributor
timestamp: April 02, 2015, 09:30:14 pm
content: I got the Fluke 884x-short. Attached are photos which show the layout. There are thick traces between the Hi-Lo sense terminals and the Hi-Lo force terminals (about 60 mils) and a thin trace (about 10 mils) connecting the force and sense sides.* PCB is .1 inch (2.54 mm) thick* Weight: 14.7 g

author: acbern
author_rank: Frequent Contributor
timestamp: April 02, 2015, 10:59:04 pm
content: I am using these (fluke 884x, keithley has the same under its own name) as well and moved away from thick copper plate shorts as shown in this thread. mostly driven by the fluke app note.while it is ok (convenient) to use a bare copper wire to calibrate a 3458a, for day to day work with it, the fluke is just better.for a 34401 the issue is neglectable though, because of its resolution/accuracy.

author: Tj138waterboy
author_rank: Regular Contributor
timestamp: July 30, 2019, 08:36:57 pm
content: Quote from: TiN on January 28, 2015, 11:31:54 amDid you happen to make modules for different manufacturer spacings and maybe still have the gerbers?

author: Kleinstein
author_rank: Super Contributor
timestamp: July 30, 2019, 08:48:54 pm
content: The pin configuration is pretty much standard on modern meters. So the Fluke short should also fit Rigol and Keysight.there is nothing really magic about the simple 4 wire short to adjust 4 wire ohms. It can be carved from a piece of copper clad board (not just leave all the copper), or made with a piece of isolator and than using 3 pieces of wire in an H shape.The tricky version it the symmetrical 4 contact short that could be turned in any direction. These do exist, but are more tricky and less accurate.

author: The Soulman
author_rank: Super Contributor
timestamp: July 31, 2019, 11:48:39 am
content: Some more info is here:https://www.eevblog.com/forum/oshw/4-wire-short/The spacing between force and sense terminals isn't standardized.I'm liking your idea tho.

author: iMo
author_rank: Super Contributor
timestamp: October 26, 2019, 12:11:27 pm
content: How the "adjusting" of the 34401A actually works?Provided I've got 10V source and 10k resistor, and I want to "DIY adjust" my 34401A's 10V and 10k ranges.I cannot find the details on the procedure, though. I do not want to start to play with the "Calibration" Menu items before having a good understanding what the meter would request me..My current understanding is it will ask me to connect 10V (or 10k) and then to enter (via the front panel keypad) the "exact values", like "10.001.345V" or 9.999.887ohm".Is my above expectation somehow correct?

author: Dr. Frank
author_rank: Super Contributor
timestamp: October 26, 2019, 12:20:56 pm
content: Quote from: imo on October 26, 2019, 12:11:27 pmPlease get the service manual, 34401-90013.pdfThe calibration procedure is explained in great detail from page 76 onwards.Remark: It is necessary to perform the zero calibration first!Frank

author: iMo
author_rank: Super Contributor
timestamp: October 26, 2019, 12:32:50 pm
content: I've seen that, not sure what it asks for, ie. in the point 5QuoteDo you dial in the "your number", or you just select "10V" from a list?

author: Dr. Frank
author_rank: Super Contributor
timestamp: October 26, 2019, 12:37:31 pm
content: that works exactly as the manual number entry of e.g. the Min/MAX, Null Value, etc., i.e. the default is 10.00000, then you select the digit by <> and then increase/decrease the value until it matches your references value.Frank

author: iMo
author_rank: Super Contributor
timestamp: October 26, 2019, 12:39:47 pm
content: And what could be the "spread" of the Vref, Rref you may dial in?

author: Dr. Frank
author_rank: Super Contributor
timestamp: October 26, 2019, 12:42:26 pm
content: Sorry, RTFM!0.9 ... 1.1 Full Scale, where Full Scale is e.g. 10.00000 V

author: HighVoltage
author_rank: Super Contributor
timestamp: May 01, 2022, 10:04:11 am
content: Quote from: baoshi on January 27, 2015, 04:33:38 pmAfter many years of looking out for theAgilent 34172A Calibration Short, finally one showed up and I was lucky to get it. This one came brand new in the original bag.However, after opening it up, I was a little disappointed.I did not expect a soldered wire inside.But it seems this was good enough for Agilent at the time.Well, at least now we know how it looks inside.

author: HighVoltage
author_rank: Super Contributor
timestamp: May 01, 2022, 10:45:43 am
content: I just hooked the 34172A short up to a warmed up 34410A in:- 4W Ohm Mode- 100 NPLC,- Offset Comp. ON- 100 Ohm range (lowest)It started with000.000,7Ohm and took about 1 min to move to000.000,0and just sits there very stable.

author: DC1MC
author_rank: Super Contributor
timestamp: May 01, 2022, 10:58:50 am
content: How much for this gem of an Agilent technology?Cheers,DC1MC

author: HighVoltage
author_rank: Super Contributor
timestamp: May 01, 2022, 11:26:40 am
content: 30 Euro including shipping for.Well, new price was maybe 10 fold?At least now we know how the Agilent metrology magic looks inside.

author: tggzzz
author_rank: Super Contributor
timestamp: May 01, 2022, 11:59:45 am
content: Quote from: HighVoltage on May 01, 2022, 10:45:43 amWith OComp on, I would be worried if it didn't!What is it like on DCVolts, Null off, Autozero on, 100NLPC ? With Stats on, you could see the min/max (and avg/std dev).Yes, I like the 34410A's stats display; it often saves uploading to a computer for post-processing.

author: HighVoltage
author_rank: Super Contributor
timestamp: May 01, 2022, 02:15:11 pm
content: Quote from: tggzzz on May 01, 2022, 11:59:45 amSame display value with Offset Comp OFF000.000,0 to 000.000,1About 79 uOhm on average stats display.

author: HighVoltage
author_rank: Super Contributor
timestamp: May 01, 2022, 02:23:33 pm
content: Here are some pictures of the original FLUKE short block for comparison.

author: HighVoltage
author_rank: Super Contributor
timestamp: May 01, 2022, 02:31:42 pm
content: Quote from: tggzzz on May 01, 2022, 11:59:45 amYes, the stats display of the 34410A and 34411A are just perfect.Voltage readings withe theAGILENTshort installed:- Average: 962 nV- Max: 1,13 uV- Min: 743 nV- StdDev.: 85 nV

author: HighVoltage
author_rank: Super Contributor
timestamp: May 01, 2022, 03:03:10 pm
content: Same Voltage readings withe theFLUKEshort installed on the 34410A:- Average: 668 nV- Max: 850 nV- Min: 508 nV- StdDev.: 65 nV

author: tggzzz
author_rank: Super Contributor
timestamp: May 01, 2022, 04:06:52 pm
content: My Agilent 34410A with the Bulgarian short was initially -1.14µV to +1.2µV.After a few hours to stabilise, it was +0.56µV to +1.11µV, mean .85µV, std dev .08µV.So, pretty similar to yours.