standard resistance values (logarithmic scale)
Hi· Can· any help me with this question.· What number or what scale do I use to generate the 10% preferred or standard resistor values?
··· jonw
··· jonw
Comments
I'm not sure what you mean by a scale or number. I generally use a table like that below for referencing all the various standard resistor values:
http://www.sizes.com/materls/resistorVal.htm
Regards,
Bruce Bates
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The logarithmic scale with 12 values is based on 10^(k/12) for values of k from 0 to 11. Those are to be rounded off to the nearest integer. But when you do that, you will find it generates the series 10,12,15,18,22,26,32,38,46,56,68,83. There is a discrepancy in the values in the middle. This is a historical accident, simply a matter of convention. The same discrepancy happens in the 5% resistor series. However, the 1% resistor series is exact and follows the rule 10^(k/96) for k=0 to 95, rounded off to an integer. There are no discrepancies.
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Tracy Allen
www.emesystems.com
'{$STAMP BS2pe} '{$PBASIC 2.5} ' generates the 1% resistor sequence ' Tracy Allen, EME Systems root96 CON 63983 ' 65536/[noparse][[/noparse]10^(1/96)], nintysixth root of ten wx VAR WORD ' for high precision calculation wy VAR WORD ' resistance values rounded off to 3 digits idx VAR WORD idx0 VAR idx.BIT0 ' for trick, empirical for best result wx=65000 FOR idx=1 TO 97 ' 96 values plus one in the next decade 100-->1000 wy=wx + 32 - idx0 / 65 ' DEBUG DEC 97-idx, TAB,DEC wx,TAB DEBUG DEC wy,CR wx = wx ** root96 + idx0 NEXT END
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Tracy Allen
www.emesystems.com