Electronics > Metrology

Scanner/Multiplexers for voltage references

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branadic:
Hi folks,

multiplexing between different voltage references is neat for automated test setups.
So while some of you have already build the DIY Low Thermal EMF Switches, others owned an expensive Dataproof scanner such as Model 160, 164 or 320, I tested my Prema 2080, which can be configured for 80x common ground, 40x 2W measurement or 20x 4W measurement, for thermal emf.

Therefore, I shorted two channels on one of the D-sub50 connectors on the back, connected K2182A to its output and switched between both channels. The connector on the back was -  metrology-like - covered with a towel and a Lemo - PTFE cable - Stäubli SLS4-B connector 22.2642-* connected scanner and nanovoltmeter.

Turns out the emf measured is <<100 nV and thus good enough for measurements on voltage references in the typical 10V range, even with a 8.5-digit meter. The scanner uses G6AK-234P-ST-US 12V relay. I received the full schematics of the scanner on request at Prema, which is basically used the same way in Prema 5017 SC.

So here you have it, even though it is specified to have 1 µV typ. and 2 µV max after 1.5h warmup only, it performs much better than expected.

What is your solution?

-branadic-

TiN:
Not bad, thanks for data.

How was TEMF measured? Was is just 2182A measure scanner output with direct cable, and select CH1 or CH2 shorted inputs? How short was made?

Perhaps more details on method, to allow reproduction by other scanners?

Mickle T.:
Prema Type 2000 10x4W scanner have about the same 100-200 nV TEMF offset.

branadic:

--- Quote ---How was TEMF measured? Was is just 2182A measure scanner output with direct cable, and select CH1 or CH2 shorted inputs? How short was made?
--- End quote ---

As I said, I made a D-sub50 connecter with a short on channel 1 and 2 using copper wire and standard leaded solder, so nothing special or low thermal. The setup was warmin up overnight and the connector covered with a towel.
K2182A was read via serial interface and GNU Ocatve, while P2080 was switched manually. Prior to measurement ACAL on K2182A was performed and measurement done using Rel button, while Ch2 was active on P2080. Hope that answers your question?


--- Quote ---Prema Type 2000 10x4W scanner have about the same 100-200 nV TEMF offset.
--- End quote ---

Ah, thanks MickleT., is that the scanner with the fancy unobtanium relay you showed some years ago in another thread?

-branadic-

TiN:
Abovementioned Data Proof 160A results. It is version without silly connectors on the back, just pure copper single-strand cables come out to the DUT.



Data points collected with Keysight 34420A nVM on 1mV range CH1, NPLC100. nVM measure A-B HI difference, while LO is shorted with copper bar (just like photo shows)



Pretty happy with results. I might replace relay board that house CH5,CH6,CH7,CH8 relays with spare board, to rectify higher TEMF for these channels.

But even bad CH8 is still within maximum vendor spec, just a tiny bit under 35nV. 35nV error in case of 10V DC voltage measurement error would translate into 0.0035 ppm, which can be ignored for all practical reasons.

Looks inside, with massive metal lid removed from isothermal box for clarity:



Latching relay card:



Rest of teardown photos are in ancient ManateeMafia's article.

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