Electronics > Metrology

DIY Low EMF cable and connectors

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leighcorrigall:

--- Quote from: OscarM on February 10, 2022, 07:41:43 pm ---Is there any merit in connectors like this?

--- End quote ---

I work with K-type and S/R-type thermocouples for high-temperature applications because they are standardized. These 'copper' types are unfamiliar to me.

I think there is some potential with using FMTC-CU-M as jacks. However, I would be careful about what 'pure' copper means. All metals are alloys and thermocouples work on the uniqueness of coupled alloys to make a thermal sensor.

Looking at the available thermocouples that LABFACILITY manufactures, there are no Cu/Cu types -- only Cu/Cu-alloys:
https://www.farnell.com/datasheets/2371070.pdf

This may suggest that the connectors you propose are actually pure copper (i.e., C101 or C110) and are used generically for all Cu/Cu-alloy thermocouples available (e.g., Cu/Cu-Ni and others). This is possible because typical thermocouples do not have a high tolerance (unless well characterized and used under the specified temperature range to prevent oxidation). For example, I usually assume a > ± 5 °C on K-types below 800 °C. When using these extension/generic connectors for general measurements, it is good enough.

Furthermore, I would be concerned also with the connection quality too. They might not be as reliable as one would need for metrology-grade measurements. That being said, I have never had a problem with MINI jacks when using them for temperature measurements. Buy the high-quality brand-name ones though.

More information at: https://www.thermocoupleinfo.com/

Conclusion: Give it a try, but make certain that the material is actually pure copper.  :-+

P.S. How are you going to clean the female connector with corrosive deoxit and expect the connection to remain consistent?  >:D

leighcorrigall:

--- Quote from: OscarM on February 10, 2022, 07:41:43 pm ---I have also seen a version with round pins which is larger.

--- End quote ---

Those are standard-size thermocouples:

https://www.omega.ca/en/temperature-measurement/temperature-connectors-panels-and-block-assemblies/temperature-connectors/ostw-cc/p/OSTW-CC-C-F

The TC jacks you were suggesting as a substitute for banana jacks are called MINI.

mendip_discovery:
I use them in the Calibration world as they are universal connector. Often used on the end of a simulator to plug into a display.

You can get then in male/female options etc. Even in slightly larger sizes.

OscarM:

--- Quote from: leighcorrigall on February 11, 2022, 03:49:09 am ---
--- Quote from: OscarM on February 10, 2022, 07:41:43 pm ---Is there any merit in connectors like this?

--- End quote ---
P.S. How are you going to clean the female connector with corrosive deoxit and expect the connection to remain consistent?  >:D

--- End quote ---
I was going by pp.128 of the Keysight 34420a manual.
Here, Keysight suggests putting a drop of Deoxit in the contacts of the Lemo connector.
Those contacts are copper.
They don't say remove it afterwards. In fact they end with 'Engage and disengage several times to distribute...'
They also don't specify which Deoxit product to use which is a whopping drawback.
Perhaps they mean the 'shield' version?
If you don't like Deoxit (whichever one it turns out to be) there is always Santovac 5. Very viscous and about as inert as anything.
Sadly I cleaned my diffusion pump and haven't filled it again.
Santovac 5 won't remove oxidation but it will probably prevent it if applied to new parts which is really what we are talking about here.

To test, I can either restore my HP 419A or use my HP 3456A. Neither may be ideal but they are on hand.
Tentative test plan:
1) Measure resistance of a loop using some of said parts once lubricated. Perhaps 5 mated pairs.
2) Measure Seebeck of said loop after, I don't know, heating up one side of the connector with a hot air pencil or heating up one connector with a hot air gun and then immediately mating them.
3) Put parts on shelf
4) Repeat after a month.
Constructive criticism of test plan welcomed.

1audio:
it should be pretty obvious if there is a contact issue. Copper to copper Seebeck is nanovolts, Copper to copper oxide is millivolts. The only issue with the test is making sure only one contact pair is heated. if both are you may have cancellation. I hope it works out.

Looking into Deoxit  https://www.hagensieker.com/wordpress/2018/06/18/deoxit-what-is-it-what-isnt-it/   it seems that there are little or no corrosives in it. Its seems more to preventing corrosion. For copper that is badly oxidized I used some Brasso and then cleaned everything with isopropyl. It seems to work quite well. I would not do this unless the connector is really brown or green and otherwise a lost cause. It worked well with my vintage Keithley 148.

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