Electronics > Projects, Designs, and Technical Stuff

Yet another resistance decade box

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Alex Nikitin:

--- Quote from: bitseeker on August 08, 2016, 08:48:05 pm ---Hi Alex,

Thanks for sharing your measurements. I was also planning on arranging my resistors as you described toward the end of your post (lowest error for 1, next-lowest for 2, etc.).

--- End quote ---

That is not the best approach, as you need to take into account the sign of the errors. For example, you have three resistors, 10.0015K, 10.002K and 9.997K, with the errors of +1.5, +2 and -3 Ohm. The most accurate arrangement will be 10.0015K, 9.997K and 10.002K, not in the order of the error magnitude! So each next resistor should be chosen for the smallest possible total resistance error at that position.

Cheers,

Alex

Alex Nikitin:
A little update. After measuring the accuracy of the decades, I've decided to build up the better one up to full 6 digits and after finishing it, just for fun I set it as close as possible to the measured 1000000 ohm value and left HP3458A logging data at NPLC100. Here is the result for 2.5 hours and some photos. As you may see, the difference between the set and the actual value here is 23 ohm, or 23ppm from 1M.

Cheers

Alex

bitseeker:

--- Quote from: Alex Nikitin on August 09, 2016, 11:34:06 am ---That is not the best approach, as you need to take into account the sign of the errors.

--- End quote ---

Yes, certainly. The way I wrote it wasn't all that clear.

ivaylo:
@Fortran, got mine, thank you so much...

Fortran:
Great :)

There's still lots of 1% kits left if anyone wants.

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