CERN 10 mA std current source article and explanation need - Page 1
Forum section: electronics / general

author: Overspeed
author_rank: Frequent Contributor
timestamp: November 23, 2024, 07:38:09 pm
content: HelloI have located this article on a standard current source ''transportable '' 10 mAThis source is use in the CERN in SwitzerlandQuestion as there is just basic schematic without components values / ref :Does that feasible to duplicate it for test , the circuit 1 to 10 mA ?the picture of the PCB looks far more complicated than the schematic but performances looks impressiveRegardsOS

author: aronake
author_rank: Frequent Contributor
timestamp: November 24, 2024, 08:39:57 am
content: Very interesting! Would be nice with schematics for thisone!

author: bnz
author_rank: Regular Contributor
timestamp: November 24, 2024, 09:41:38 am
content: Here the standard in action "The Upgraded CERN DC-current Calibrator"Slides:https://indico.cern.ch/event/1467419/contributions/6178242/attachments/2946917/5185067/beev_tcc_171024.pdfArticle behind the pay wall:https://doi.org/10.1109/CPEM61406.2024.10646117

author: Kean
author_rank: Unknown
timestamp: November 24, 2024, 09:48:54 am
content: Also mentioned in the 2021 Metrology Conference slides by John Pickering of Metron Designshttps://docs.ampnuts.ru/eevblog.docs/eBooks/Metrology Conference 2021/4. John Pickering Metrology Meeting.pdf

author: J-R
author_rank: Super Contributor
timestamp: November 24, 2024, 10:14:03 am
content: Took a look at the document behind the "paywall' and no schematic.

author: Overspeed
author_rank: Frequent Contributor
timestamp: November 24, 2024, 12:49:36 pm
content: HelloAn article on another current source similar which focus on ultra low noise with the schematicThe CERN source seems to be manufactured by the J Pickering company in UK , so perhaps the schematic is proprietary ?RegardsOS

author: Kleinstein
author_rank: Super Contributor
timestamp: November 24, 2024, 01:56:49 pm
content: One small part to improve in the Cern 10 mA article would be to not use TaN resistor arrays, but NiCr based ones. There is a chance that this change was also done in thestep from version 2 to 3 at Cern. They actually had a comparison of resistor arrays done at Cern and found usually more excess noise for the TaN types.The product / schematics may be proprietary. There is still nothing really secret, new. The kind of amplifying current mirror is also used with DMMs, like in the HP34401, though usually for lower currents and maybe for a different reason (to get stable current over a larger range) and not so much with the heating problem.

author: Overspeed
author_rank: Frequent Contributor
timestamp: November 24, 2024, 08:19:58 pm
content: HelloChinese make something similar , PCB looks to be less populated that the CERN designI link the docRegardsOS

author: Overspeed
author_rank: Frequent Contributor
timestamp: November 24, 2024, 08:56:31 pm
content: Quote from: Kleinstein on November 24, 2024, 01:56:49 pmHelloin this post ,https://www.eevblog.com/forum/metrology/a-stable-battery-powered-1ma-current-source-for-measurement-of-10k-standard-resi/?nowapThe design for a1 mAlooks classic and provide quite good performances.The voltage source can be perhaps improved by using a LTZ ( if the improvement is really demonstrated regarding the cost ?)Resistor can be upgraded I agreeA real PCB with a real ground all-around can be designed and shielded / insulatedLast point is the current amplifier as the CRN board looks ''complicated'' but perhaps there is easier solutions ? but often evil in detailsRegardsOS

author: branadic
author_rank: Super Contributor
timestamp: November 24, 2024, 09:44:18 pm
content: PBC2 is basically a modified version of the original W/F7000, so you can look into the reverse engineering by chekhov. PBC3 is however further modified using ADR1000 instead of LTZ1000.-branadic-

author: Kleinstein
author_rank: Super Contributor
timestamp: November 24, 2024, 11:16:21 pm
content: II don't see that the current amplifier is complicated. The two SO14 chips are likely the resistor arrays, not active chips. It may be a bit unusual to still use discrete transistors, but this should not be that bad and the parts are cheap. At least for this part they have a pretty complete plan - finding suitable resistor values should be relatively easy.Chances are that what is labeled as a charge pump in the original may now be a boost converter. At least there is a inductor and not many capacitors.If the main target is a 10 mA current, one may be able to skip the 7 to 10 V step and have die current source directly with 7 V.A point one could consider is a proper 4 wire access to the ref. resistor for the 1 mA current.The 1 mA current source is classic, but may not tolerate a highly inductive target and not sure how it reacts to possibly disturbance from a flux gate based current transformer as a target.

author: guenthert
author_rank: Frequent Contributor
timestamp: November 25, 2024, 09:07:21 am
content: Quote from: Kleinstein on November 24, 2024, 11:16:21 pmCan't a resistor be put in line as a work-around as long as the compliance voltage isn't exceeded?

author: Kleinstein
author_rank: Super Contributor
timestamp: November 25, 2024, 09:17:58 am
content: A series resistor (or RL combination as in many DMMs), especially in combination with some RC to "ground" could be used to make the current source more tolerant to inductive loads and filter some interference.

author: Overspeed
author_rank: Frequent Contributor
timestamp: November 25, 2024, 09:39:51 am
content: Helloan article on the subject with detail ( LTZ , Vishay foil ..) with the schematics for this project ( not the CERN circuit )RegardsOS

author: Overspeed
author_rank: Frequent Contributor
timestamp: November 25, 2024, 10:54:37 am
content: Quote from: Kleinstein on November 24, 2024, 11:16:21 pmHelloMy assessment was between the basic schematic published and the picture of the real PCB as in precision system each components can have a effect on the result , I have built several current sources from basic TL431 + transistor to high quality IC with foil resistor various tests , but my quest to built the ''best I can '' 10 mA source continue.RegardsOS