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1V Reference @ 1ppm

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Kleinstein:
The Mercury reference cells are just 2% higher than 1 V. So it might still work. With such an old meter this might have well been the reference of choice at that time. Even if one had to divide down to exactly 1 V, it would help starting at just 1.019 V - the divider resistors would be responsible for only 2% and thus something like 12 times less critical than in a 1.25 V to 1 V divider.

An accurate 10 V reference and Hamon type divider (accurate 1:10) could be an option too.

Wolfgang:

--- Quote from: Rafael on January 26, 2019, 12:22:53 am ---Hello,

Does anyone have any suggestions on how to find / build a 1v @ 1ppm reference?

Thanks a lot!

--- End quote ---

If you are serious there is but one choice: Make a Josephson standard. All other stuff is a crippled compromise. 1ppm is below everything you can buy from renowned companies. And dont forget to join the TEA and the voltnuttery forums.  :wtf:  >:D

beanflying:

--- Quote from: Kleinstein on January 28, 2019, 07:01:54 pm ---The Mercury reference cells are just 2% higher than 1 V. So it might still work. With such an old meter this might have well been the reference of choice at that time. Even if one had to divide down to exactly 1 V, it would help starting at just 1.019 V - the divider resistors would be responsible for only 2% and thus something like 12 times less critical than in a 1.25 V to 1 V divider.

An accurate 10 V reference and Hamon type divider (accurate 1:10) could be an option too.

--- End quote ---

Can you still buy Mercury batteries in the EU or only from suspect sources?

Building a Hamon Divider for myself too when Mr Pettis catches up a bit  8)

ArthurDent:
Here is a photo of the first of my two LTZ1000ACH 10 volt buffered references. It has been powered on and aging for months and is pretty damn stable. When in use it will only be run on battery power to avoid any possible offsets caused by any stray coupling caused by the power lines. Even with all the care I've used to construct this standard it still has to be adjusted and measured and no matter what I do it will fall short of 1 ppm.

If you can get 10 volts it is simple to divide it down to 1 volt.

Kleinstein:

--- Quote from: beanflying on January 28, 2019, 11:02:49 pm ---
--- Quote from: Kleinstein on January 28, 2019, 07:01:54 pm ---The Mercury reference cells are just 2% higher than 1 V. So it might still work. With such an old meter this might have well been the reference of choice at that time. Even if one had to divide down to exactly 1 V, it would help starting at just 1.019 V - the divider resistors would be responsible for only 2% and thus something like 12 times less critical than in a 1.25 V to 1 V divider.

An accurate 10 V reference and Hamon type divider (accurate 1:10) could be an option too.

--- End quote ---

Can you still buy Mercury batteries in the EU or only from suspect sources?

Building a Hamon Divider for myself too when Mr Pettis catches up a bit  8)

--- End quote ---

A mercury battery (like those old coin cells) would not help that much, they are more like 1.45 V and relatively high TC. There is essentially no way to get them anymore. AFAIK they are not manufactured anymore and thus would be old and likely bad by now. The point are used mercury reference cells. These are larger and last longer and still sometimes come up on ebay or similar. However they are difficult to transport - not all of them are like transport per parcel and the transport may not be allowed anyway, because of the mercury and acid inside. The cell may still need an extra high impedance buffer and temperature compensation or stabilization.

For a Hamon divider one does not need that super stable resistors. The idea usually is to first adjust the resistors chains to be equal and than do the extra connections to go from 3:3 to 1/3:3 resistor ratio. So it needs an extra adjustment step before use. The final accuracy is like the square of the resistor ratio accuracy. So starting with 0.1 % resistors is enough to get to the ppm range. It still needs care to avoid errors from self heating, thermal EMF and leakage.

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