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| 1V Reference @ 1ppm |
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| spec:
--- Quote from: Rafael on January 26, 2019, 12:22:53 am ---Does anyone have any suggestions on how to find / build a 1v @ 1ppm reference? --- End quote --- Hi Rafael, I couldn't find a 1V voltage ref to meet your spec, so the only option is a higher voltage voltage ref, say 1V25, two resistors, and a precision opamp. You could make a miniature oven quite easily and pop the whole circuit in the oven to improve the stability with ambient temperature changes. As you no doubt know, the power supply would need to be pretty fancy, but all within practical bounds. How much current would you want to draw from the 1V reference? By the way, I am no expert on extreme high-spec voltage references, so these are just my thoughts. If you are interested in this approach, just say and we can discuss it some more. |
| tggzzz:
--- 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 --- There is a lot of information in other threads on this forum, in the metrology sub forum. Voltnuttery is expensive, very expensive. But your question is easy to answer - but is it the right question? Hint: state your problem, not your presumed solution. For reasons, see https://entertaininghacks.wordpress.com/library-2/good-questions-pique-our-interest-and-dont-waste-our-time-2/ |
| tggzzz:
--- Quote from: beanflying on January 26, 2019, 05:52:49 pm --- --- Quote from: mycroft on January 26, 2019, 05:17:40 pm ---Many, many years ago, i read an article by NBS (now NIST) on using a mercury cell as a voltage transfer standard. The major problem was temperature sensibility. I would like to find this article again. I searched a lot without success. Anyone remembers this article and has a reference? --- End quote --- Not the article you wanted but some of us still have some Standard Cells and play with them from time to time. :) https://www.eevblog.com/forum/metrology/1000-my-(hi)story-of-the-weston-cell-of-the-volt-and-of-being-a-volt-nuts/msg1039421/#msg1039421 I had mine out of the boxes a couple of days ago in 35 degrees ambient. It was 0.06mV up on last time I recorded it at about 20C and some of that drift would have been the 34401A. The un-saturated ones had a better tempco than the saturated ones. Generally run in banks and averaged when used as references too. EDIT: NIST is currently offline thanks to the USA shutdown BS but try this search on Google 'nist weston standard cells' will get you some pdf hits when it gets back up. --- End quote --- I can use my working 1949 Weston standard cells as a thermometer, 40uV/°C |
| beanflying:
--- Quote from: spec on January 26, 2019, 10:02:56 pm --- How much current would you want to draw from the 1V reference? By the way, I am no expert on extreme high-spec voltage references, so these are just my thoughts. If you are interested in this approach, just say and we can discuss it some more. --- End quote --- If it is a 'reference' the answer would be as little current as possible to maintain voltage stability. Op amp buffers can be added but generally they add to errors and tempco problems not help. There is for example a 0.01mV variation on my HP735A Transfer Standard between 10M and the GigOhm impedance settings on my 34401a so if it is being used as a transfer it has to be set to allow for this depending on the intended use. So load matters even if tiny. |
| spec:
--- Quote from: beanflying on January 26, 2019, 10:26:32 pm --- --- Quote from: spec on January 26, 2019, 10:02:56 pm --- How much current would you want to draw from the 1V reference? By the way, I am no expert on extreme high-spec voltage references, so these are just my thoughts. If you are interested in this approach, just say and we can discuss it some more. --- End quote --- If it is a 'reference' the answer would be as little current as possible to maintain voltage stability. Op amp buffers can be added but generally they add to errors and tempco problems not help. There is for example a 0.01mV variation on my HP735A Transfer Standard between 10M and the GigOhm impedance settings on my 34401a so if it is being used as a transfer it has to be set to allow for this depending on the intended use. So load matters even if tiny. --- End quote --- Yes, I do appreciate that that is a very specialist area and that 1ppm is only 1uV in 1V, so what I was going to do was to do the best I can and knock out a circuit and some notes for discussion. To my mind, the opamp is the biggest problem because choppers would be too intrusive. |
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