Hi all,
I’m wanting to build a Kelvin–varley divider, and looking for parts. I’m trying to choose a switch for the first decade, which is the important one, or at least important enough to match 10K resistors to significantly better than 0.01%.
I’m thinking that the contact resistance is important, but more important that it doesn’t change than that it’s super low. I’ve pretty-much narrowed it down to either the Grayhill series 8 (for example 08S36-02-1-10N Grayhill | Mouser Australia) or the Grayhill series 71 (eg 71B36-06A10N Grayhill | Mouser Australia)
The series 8 is physically larger, but the 2 deck flavour is $107. By contrast the 6 deck series 71 is only $50. Both are specced as “50mΩ max” per contact, so based on that the series 71 should be much better, on account of being able to parallel three decks...
Anyway, I’m very open to suggestion. These suckers are expensive, and I’d prefer to buy them once.
I’m wanting to build a Kelvin–varley divider, and looking for parts. I’m trying to choose a switch for the first decade, which is the important one, or at least important enough to match 10K resistors to significantly better than 0.01%.
I’m thinking that the contact resistance is important, but more important that it doesn’t change than that it’s super low. I’ve pretty-much narrowed it down to either the Grayhill series 8 (for example 08S36-02-1-10N Grayhill | Mouser Australia) or the Grayhill series 71 (eg 71B36-06A10N Grayhill | Mouser Australia)
The series 8 is physically larger, but the 2 deck flavour is $107. By contrast the 6 deck series 71 is only $50. Both are specced as “50mΩ max” per contact, so based on that the series 71 should be much better, on account of being able to parallel three decks...
Anyway, I’m very open to suggestion. These suckers are expensive, and I’d prefer to buy them once.
If you are using resistors of more than say 100R, I doubt you will notice the odd Ohm of contact resistance.
Grayhill are good, I have a box of them at work bought 10 years ago and they worked perfectly first time.
Trouble is the Kelvin Varley divider has 2 contacts per decade, it all adds up.
I would go for the military gold plated version, costs more... no surprise, but should stay the same for a very very long time. The other is gold over silver and if misused may not perform the same again.
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Try Electronic Surplus - Electrical, Electronics & Electromechanical Supplies -- and search Grayhill.
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