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I made an error on ordering and am receiving a shipment of 5% 100K resistors when I wanted 1%.

This is for a voltage divider circuit.

Would it help improve the precision if I put two each in parallel then put them in series to achieve the 100K?

Or would the extra parts be worse for the circuit than simply using a DMM to find the most accurate one and use that?

Please excuse me if this sounds like a dumb question. The order was wrong. It is a simple case of the computer doing what I told it to do instead of what I wanted. (Old joke, I know).

Thanks in advance for your answer(s).

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    \$\begingroup\$ Chances are that the manufacturer has already screened the "1%" resistors out of the "5%" batch. Guessing, if you were to sample many resistors you might find a population peak at -5% and another at +5%. You might screen for 2 such resistors at the opposite ends of the permitted range, put them in series then put 2 such resistor pairs in a parallel configuration. But, would it not be easier just to order the 1% resistors? \$\endgroup\$
    – st2000
    Jun 24, 2017 at 22:06
  • \$\begingroup\$ Yeah, that's what I will do. But the question seemed interesting nonetheless. I was just thinking that maybe the distribution would be Gaussian and the 1% would have a sharper peak, and that maybe by combining several I wouldn't have to accept just one that was more likely to be off-center. \$\endgroup\$
    – SDsolar
    Jun 25, 2017 at 5:25

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No, the precision remains the same regardless of the configuration. You're stuck with 5%, unless you reorder the correct parts, or you test them with a reliable DMM. I have to say that the last time I tried this, all the resistors in the batch had almost precisely the same resistance though (I can't remember the value, but say it was nominally 1K, they were all 992 ohms or something like that).

If you think about it, it has to be this way. If you could create higher precision from combining lower quality components, you wouldn't need the high precision ones in the first place...

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  • \$\begingroup\$ 5% parts have exactly the same quality as 1% parts ( re second paragraph ). I have first hand experience in resistor manufacturing, albeit from long ago, and can attest that 5% resistors are made exactly as 1% parts. At the end of production line all resistors are measured and binned according to tolerance. For 100k 5% resistors one can most likely find 95-98k and 102-105k parts. So if one is going to spend time measuring all resistors in a given lot it is possible to get 100k 1% resistor from parallel/series combination, for example combining two 96k and two 103k resistors. \$\endgroup\$
    – user117884
    Jun 25, 2017 at 18:32

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