Group buy - low thermal EMF LEMO connector for nanovoltmeter (34420/2182) - Page 1
Forum section: electronics / general

author: balage
author_rank: Regular Contributor
timestamp: September 05, 2019, 06:30:21 pm
content: Hi Guys,I am planning to buy low thermal EMF LEMO plugs for my Keysight 34420 nanovoltmeter. It is the FVN.1S.304.CLYC52Z, and the socket is the EVP.1S.304.CLY. Like in this post:https://www.eevblog.com/forum/metrology/diy-low-emf-cable-and-connectors/msg1667222/#msg1667222Would anybody join? The price for the plug would be around 80 EUR, while the socket is around 60 EUR. EU fellows are preferred, however US shipment can be somehow done, I dont have much experience in it. The drawback is that the lead time is 3 months...So?

author: Magnificent Bastard
author_rank: Regular Contributor
timestamp: September 06, 2019, 04:07:39 pm
content: Quote from: balage on September 05, 2019, 06:30:21 pmI already have a dozen of these for my 34420. Good idea though. Is there a quantity discount at some point?

author: balage
author_rank: Regular Contributor
timestamp: September 06, 2019, 06:00:29 pm
content: Quote from: Magnificent Bastard on September 06, 2019, 04:07:39 pmI hope so. I only wanna buy 2 or 3 for myself, and this is not qualifying a discount. That is why I want to check first if anybody is interested in. Nothing yet...

author: HighVoltage
author_rank: Super Contributor
timestamp: September 10, 2019, 08:19:48 am
content: At what quantity is there a benefit in discount?I am interested, if I the price is good.

author: TiN
author_rank: Super Contributor
timestamp: September 10, 2019, 08:49:22 am
content: When I was buying my set, discount qty was starting from hundreds

author: balage
author_rank: Regular Contributor
timestamp: September 10, 2019, 08:59:06 am
content: At 10 pieces each of the plug costs 75 EUR, and the socket costs 55 EUR.The next discount step is at 25 pieces. I don't even think we will have 10 pieces to order...

author: balage
author_rank: Regular Contributor
timestamp: September 10, 2019, 09:02:52 am
content: It is interesting, that Mouser hasn't got the 52 type, but has the same connector but with smaller cable diameter.https://eu.mouser.com/ProductDetail/LEMO/FVN1S304CLYC37Z?qs=sGAEpiMZZMvf6myxbP4FpFVl7gYRtuT3GHaRshj6SqA%3D

author: syau
author_rank: Frequent Contributor
timestamp: September 10, 2019, 10:11:41 am
content: https://www.mouser.com/ProductDetail/Keysight/34102A?qs=YCa%2FAAYMW003I91nmfKH%2Fg%3D%3DComplete assembly cost USD$200+

author: balage
author_rank: Regular Contributor
timestamp: September 10, 2019, 10:15:45 am
content: The shorting plug also costs terrible...But it is true for the triax cables, that you can make your own cheaper. And the quality can be the same as the original ones.

author: HighVoltage
author_rank: Super Contributor
timestamp: November 10, 2019, 07:50:16 pm
content: Hello balageAny news on this project?I would be interested in a few of these connectors.

author: balage
author_rank: Regular Contributor
timestamp: November 19, 2019, 11:59:35 am
content: Hello HighVoltage,The order is delayed, as I've started using the unplated copper binding posts, sold by TiN.However I still need the LEMOs...

author: guenthert
author_rank: Frequent Contributor
timestamp: December 15, 2019, 11:13:08 pm
content: Quote from: syau on September 10, 2019, 10:11:41 amConsider yourself lucky! The same assembly for a Keithley 181/182 (#1507) with the odd #1486 connector isn't stocked by Keithley and the regular suspects. I found one individual who asked for 600 (!) chFand others who won't publicly state the price -- one has to request a quote, which I read as "if you have to ask, you can't afford it."

author: MiDi
author_rank: Frequent Contributor
timestamp: December 16, 2019, 06:28:37 am
content: Keithley 281/282 - secret instruments?For K181/182 the connectors are Amphenol 97-3106A-16-11P and 97-3057-1008-1.E.g. AB-Precision has assemblys for ~200EUR.

author: guenthert
author_rank: Frequent Contributor
timestamp: December 16, 2019, 05:17:58 pm
content: Quote from: MiDi on December 16, 2019, 06:28:37 amDarn, yes. Corrected now in the post above to avoid further confusion. Thanks!Quote from: MiDi on December 16, 2019, 06:28:37 amHmmh, oh well, better than 600chF, perhaps reasonable even for a professional application, but still out of my budget. Thanks though.

author: MiDi
author_rank: Frequent Contributor
timestamp: December 16, 2019, 05:26:47 pm
content: Added connectors to last post for cheap DIY alternative.

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 21, 2019, 12:12:51 pm
content: If it helps any, I bought 4 x FVN.1S.304.CLYC37Z in 2016 from LEMO Benelux for EUR 46 a piece.Alan

author: balage
author_rank: Regular Contributor
timestamp: January 05, 2020, 09:29:14 am
content: I have already ordered two plugs and one socket...

author: HighVoltage
author_rank: Super Contributor
timestamp: January 05, 2020, 09:52:13 am
content: Where did you order them and how much did you pay?Thanks

author: balage
author_rank: Regular Contributor
timestamp: January 05, 2020, 12:39:07 pm
content: From the local representative of Keithley/Tektronix.For me plugs were 75 EUR each, and socket was 55 EUR.Actually these connectors with copper-made contacts are not is the catalog of LEMO, but I should have asked for them. However (as I have to pay VAT) there is only a small difference between prices I've got and LEMO Benelux.

author: HighVoltage
author_rank: Super Contributor
timestamp: January 05, 2020, 01:18:48 pm
content: I bought two original cables for the 34420A and a few 4-Pin LEMO connectors size 1.With one of these LEMO connectors I made my own short. A 2 mm thick copper wire can be squeezed between the 4-pins of the LEMO and then I soldered this one piece copper wire to all 4 pins. It seems to work well.

author: balage
author_rank: Regular Contributor
timestamp: January 05, 2020, 01:54:47 pm
content: Nice shorting plug. Is this normal solder? Or a special one?The connectors on the right, that have the locking pins. Do they fit into the sockets as well?

author: HighVoltage
author_rank: Super Contributor
timestamp: January 05, 2020, 03:08:34 pm
content: Yes, the locking mechanism fits perfectly to the receptor at the 34420A and it locks perfectly tight.I used normal solder for the copper wire to the gold plated connectors.It seems to work well and I can not notice any thermal EMF.Here are some more pictures of the short connector.

author: balage
author_rank: Regular Contributor
timestamp: January 05, 2020, 04:45:41 pm
content: Nice, great assembly!Is the type of that connector public?

author: HighVoltage
author_rank: Super Contributor
timestamp: January 05, 2020, 07:33:29 pm
content: Yes, it is a size 1 (9mm) standard LEMO connector that is very easy to source.LEMO Number:FFA.1S.3044 connectors (2 female, 2 male)

author: HighVoltage
author_rank: Super Contributor
timestamp: June 20, 2020, 12:13:30 pm
content: I have finally received an original Keysight Short plug.This is the Keysight Part number:34420-81603The retail price is:Euro 249,-Here are some pictures of the assembly.The LEMO connector is pure copper.

author: HighVoltage
author_rank: Super Contributor
timestamp: June 20, 2020, 12:19:30 pm
content: With the new original short, I calibrated the 34420A to 0 OHM and the value shown on the 34420A stays very stable between 0.000,000,0 and 0.000,000,1 even for days and with temperature changes.When I install my self made LEMO short and let the instrument settle for a few minutes, the value shown is always between 15.9 around 18.6 uOhm, depending on temperature in the lab.So, the pure copper original connector makes a difference.But this difference is larger than I had expected.

author: CalMachine
author_rank: Frequent Contributor
timestamp: June 20, 2020, 12:48:54 pm
content: Quote from: HighVoltage on June 20, 2020, 12:19:30 pmThat could potentially be coming from your shorting connection on your DIY plug

author: HighVoltage
author_rank: Super Contributor
timestamp: June 20, 2020, 01:05:02 pm
content: Quote from: CalMachine on June 20, 2020, 12:48:54 pmAgree...Although I use a pure copper rod, squeezed it between the 4 solder studs and made sure I had a good mechanical connection to all 4 gold plated studs. Then added solder.I should try a different configuration.Here is a picture of my gold plated LEMO connector with copper rod soldered to all 4 studs.

author: dietert1
author_rank: Super Contributor
timestamp: June 20, 2020, 02:14:34 pm
content: Instead of trying to simulate a 4W ohms measurement of a short, you could try to make two independent shorts for drive and sense, maybe with a 1 KOhm resistor between the two shorts. In order to keep the drive current separate. And the original has that plastic sleeve around the "thermal head".Regards, Dieter

author: martinr33
author_rank: Frequent Contributor
timestamp: June 21, 2020, 03:21:24 am
content: If the pins are gold plated, then they are brass not copper. I have both brass and copper pin shorts, so I will have to try measuring both. Maybe you could also check for the voltage measured across the short?I ran a quick test on a 34420a that I have had running for a couple of weeks using shorts that I made. The Lemo short uses cadmium-tin alloy. These are built as a 4-way short.Copper pin Lemo connector with nut: -12nV 0.2nRBrass pin Lemo clone push/pull -7nV 0.3nRI'd trust the Lemo copper pin as the better of the two, but the differences are very small.The clone shorts are very convenient because of the push/pull connection.