Products > Test Equipment
LM399 Voltage Reference, Fluke 289, Gossen 29S, RM303, AN870
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Trader:
Just sharing an experiment...  There are awesome Voltage References as "DMMCheck Plus" and "PDVS2mini 20bit", and also cheaper options like AD584 and LM399.

I got an LM399 on Aliexpress, I was waiting for a good product and (very important) a Precise Calibration. I tested a very new Fluke 289, Gossen 29S, Richmeters RM303, and Aneng AN870.

None of them exactly matched the LM399, but the difference is between 0.02% and 0.01% (or 1/10,000), an excellent precision!!!

I'm happy that Fluke and Gossen exactly matched ALL the measurements (both have a Calibration certificate and they scored exactly 5.0000 VDC). Also, the chinese DMMs performed Very Well.

I think a factory produces a bunch of LM399 references and each seller is responsible to manually calibrate it. I saw some pics with the Voltages printed, handwritten, or even photocopy. Maybe (maybe) the seller uses a regular DMM and "create a fake decimal value", like 5.000V "un-rounded" to 4.99955V.

Also, even with a stable 15V input and constant 24C temperature, there is a voltage fluctuation of +- 0.1mV.

In summary: get a good quality Voltage Reference, Correctly Calibrated by a Trustable seller, unfortunately, on Aliexpress not only the products and specs can be fake, but also the Services. Now, I need to find somewhere a +6 1/2 digits DMM to check the correct calibration.  :(
masterx81:
I've a similar chinese LM399 reference, and neither match my in calibration 34401a 😂😂
Trader:

--- Quote from: masterx81 on December 25, 2020, 09:30:00 pm ---I've a similar chinese LM399 reference, and neither match my in calibration 34401a 😂😂

--- End quote ---
Post 399, a subliminal reference msg? LOL
Martin72:

--- Quote ---Now, I need to find somewhere a +6 1/2 digits DMM to check the correct calibration. 
--- End quote ---

Why ?  ;)

The values of your calibrated multimeters matching nearly perfect to the values from the reference, written on the board.
However they don´t trim it to 2.5, 5, 7.5, 10V.
They obviously measured only the voltages without trimming anything and write it down.
And you know the accuracy of the giving values.
If you got 5.0000V and measure 5.0000V or you got 4.9777V and measure 4.9777V...What´s the difference inbetween ?  8)
TiN:
You could get 5.0000 V known to +/- 100ppm or 4.9777V with uncertainty +/-10 ppm. Obviously second measurement would be more trustworthy. Listing values without uncertainty attached to it is just speculation digits and not defining a measurand.
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