CERN 10 mA std current source article and explanation need

[Overspeed]

Hello

I have located  this article on a standard current source ''transportable '' 10 mA

This source is use in the CERN in Switzerland

Question 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 impressive

Regards
OS

[aronake]

Very interesting! Would be nice with schematics for thisone!

[bnz]

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.pdf
Article behind the pay wall:
https://doi.org/10.1109/CPEM61406.2024.10646117

[Kean]

Also mentioned in the 2021 Metrology Conference slides by John Pickering of Metron Designs

https://docs.ampnuts.ru/eevblog.docs/eBooks/Metrology Conference 2021/4. John Pickering Metrology Meeting.pdf

[J-R]

Took a look at the document behind the "paywall' and no schematic.

[Overspeed]

Hello

An article on another current source similar which focus on ultra low noise with the schematic

The CERN source seems to be manufactured by the J Pickering company in UK , so perhaps the schematic is proprietary ?

Regards
OS

[Kleinstein]

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.

[Overspeed]

Hello

Chinese make something similar , PCB looks to be less populated that the CERN design

I link the doc

Regards
OS

[Overspeed]

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.

Hello

in  this post ,

https://www.eevblog.com/forum/metrology/a-stable-battery-powered-1ma-current-source-for-measurement-of-10k-standard-resi/?nowap

The design for a 1 mA looks 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 agree
A real PCB with a real ground all-around can be designed and shielded / insulated

Last point is the current amplifier as the CRN board looks ''complicated'' but perhaps there is easier solutions ? but often evil in details

Regards
OS

[branadic]

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-

[Kleinstein]

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.

[guenthert]

[..]
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.

   Can't a resistor be put in line as a work-around as long as the compliance voltage isn't exceeded?

[Kleinstein]

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.

[Overspeed]

Hello

an article on the subject with detail ( LTZ , Vishay foil ..) with the schematics for this project ( not the CERN circuit )

Regards
OS

[Overspeed]

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.

Hello

My 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.

Regards
OS