Information on B2-38/B2-39/V2-38/V2-39 Nanovoltmeters - Page 1
Forum section: electronics / general

author: Echo88
author_rank: Frequent Contributor
timestamp: September 01, 2021, 11:37:05 am
content: Chekhov mentioned in the Chat that the nanovoltmeters mentioned in the titel supposedly use special photoresistor-optocouplers.The known HP419A comes to mind, which also uses such a technique.Does anyone have more infos on those nanovoltmeters?https://zapadpribor.com/en/v2-39/https://zapadpribor.com/en/v2-38/

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 01, 2021, 12:46:54 pm
content: Quote from: Echo88 on September 01, 2021, 11:37:05 amThis link has a few words about input optocouplers.https://radiokot.ru/forum/viewtopic.php?p=3846393.However, you can't find them now. And the old ones are already degraded.The repair is described herehttps://radiokot.ru/forum/viewtopic.php?f=10&t=134327&view=nextSo rather the question is what are you looking for? It might be easier to find

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 01, 2021, 01:03:11 pm
content: http://www.mediafire.com/file/05dalvoaeax8be2/B2-39.rar/file

author: strawberry
author_rank: Super Contributor
timestamp: September 01, 2021, 01:23:10 pm
content: this part ОЭП-26 ?by the construction seems good but some custom chips might be a problem for repair

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 01, 2021, 01:28:59 pm
content: В2-38 PART1Rename to v2-38.zip.z01

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 01, 2021, 01:30:11 pm
content: В2-38 PART1Rename to v2-38.zip.zipUnzip multipart arhive.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 01, 2021, 01:31:21 pm
content: Quote from: strawberry on September 01, 2021, 01:23:10 pmThey live ten years. Fifteen at the most. There are no new ones. The old ones are already degraded

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 02, 2021, 03:58:55 am
content: I have full set of documentation for В2-39 (V2-39) nanovoltmeter. And also some internal documents describing the testing of this nanovoltmeter.But I need to ask permission to share them. If permission is granted, I will share this documentation.I'm attach brief info for optocouplers used in modulator.P.S. If you want to get one of these devices, you better look for B2-38 - you can really find it. B2-39 is unobtanium.P.P.S. These optocouplers are currently not produced. But the production line remained and mothballed. Theoretically, with a large order, these optocouplers can be produced.

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 03, 2021, 12:51:44 pm
content: Input block of the B2-38 nanovoltmeter.Modulator based on optocouplers (optocouplers are installed in a massive copper block). And the transformer to which the input modulator is loaded.

author: Echo88
author_rank: Frequent Contributor
timestamp: September 03, 2021, 12:56:53 pm
content: Some massive copper goodness

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 04, 2021, 05:28:57 am
content: A quick overview of how a 30-year-old B2-38 is measuringFor this check, theNK4-1calibrator was used as a source.Rsource = 1 Ohm.P.S. Some historical background:В2-38 was developed in MNIPI in the early 80s. The device began mass production in 1984.This nanovoltmeter is also equipped with a GPIB interface.P.P.S. Please pay attention, the device contains original optocouplers OEP-26, which are currently in very poor condition. The shelf life of these optocouplers is not more than 10 years, this is due to the chemical composition used for the manufacture of the photoresistor.That is, the device now has worse characteristics than those that were when the optocouplers were new.

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 04, 2021, 07:05:03 am
content: I recorded a short video to demonstrate the measurement of 15nV with a B2-38 nanovoltmeter.

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 04, 2021, 07:39:49 am
content: V2-38 reading with input short.

author: Vgkid
author_rank: Super Contributor
timestamp: September 04, 2021, 01:53:12 pm
content: How do you connect the calibrator to the nV meter?

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 04, 2021, 02:25:51 pm
content: Quote from: Vgkid on September 04, 2021, 01:53:12 pmI think a photo is the best way to show it.A 1Ω resistor is installed in the brown box

author: bsw_m
author_rank: Frequent Contributor
timestamp: October 03, 2021, 12:37:43 pm
content: Hi! I scanned one book of four books descriptions of the B2-38 device.Book "Technical Description". Can be downloaded from:https://disk.yandex.ru/d/3pN6X0dBsi8AUwPlease note: Russian language!

author: ZhuraYuk
author_rank: Regular Contributor
timestamp: August 25, 2022, 06:38:26 pm
content: Here is example of DIY photo relay which is working good as replacement for original OEP26 photoresistors which are usually dead after 40 years. It is installed in the housing of original photoresistor and filled with thermally conductive glue.Main advantages comparatively to industrial photo relays are that they have much lower capacity and charge injection. After replacement the noise is 1nV and zero stability is excellent.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: August 26, 2022, 08:27:18 am
content: Quote from: ZhuraYuk on August 25, 2022, 06:38:26 pmHow stable is the zero of a closed relay depending on temperature?

author: macaba
author_rank: Regular Contributor
timestamp: August 26, 2022, 09:22:36 am
content: Quote from: ZhuraYuk on August 25, 2022, 06:38:26 pmVery nice, the capacitance vs. on resistance ratio of the FDC6303N looks good. Did you take any measures of turn-on/turn-off time?

author: ZhuraYuk
author_rank: Regular Contributor
timestamp: August 26, 2022, 02:52:53 pm
content: Quote from: MegaVolt on August 26, 2022, 08:27:18 amI did not conducted such testing. The shorted nanovoltmeter stayed near open window whole night and zero has moved by 1-2nV. Temperature change was about 5 degree C. Whole analogue board of the nanovoltmeter is closed in hermetic chamber with thick plastic walls. So I assume thermal conductivity is very low.Quote from: macaba on August 26, 2022, 09:22:36 amI did some testing and turn on time is very low unable to measure. Turn off time depends on gate discharge resistor value, in my schematic it is 1ms, For 82Hz modulation in V2-38 this is fast enough.Input-Output capacity of DIY is 0.05 pF. OEP26 have about 0.01pFHere is how voltage picture on DIY optorelay looks.Here is how voltage looks on LEDsAnd here how photoresistor voltage is expected to look like in factory service manual. Modulation depth 50% in best case (nV range) and 20%(1V range) in worst