BestPair III now does 0.1%, 1% and 5%

Hi, BestPair Voltage Divider Resistor Pair Picker now calculates results for

0.1%, 1% and 5% (E192, E96, and E24) resistor value sets.

There are 480,000 different combinations of standard 1% resistor values. If you need 2.75 volts from a

5.00 volt reference, which of those 480,000 pairs will give you the closest result?

For this example there are 9 resistor pairs that will get you to within

0.5%, but one resistor pair will get you within 0.15%. Only 1 out of 480,000 combinations is the very best pair!!

The Best Pair III resistor calculator program will calculate and display the twenty one best voltage divider resistor pairs, as well as the error voltages, percent error, "Perfect R2" and "R Thevenin" values. Results can be scaled to any decade of course.

If you are interested you can get it with instant download delivery here -->

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Thanks for looking.

Cheers, Tim

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Reply to
Tim
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If you do this:

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Reply to
John Fields

Magic ofcourse!!!

Reply to
Abstract Dissonance

Oh give a dog a bone! ;-) He means that the error contribution from the granularity of resistor value choice is reduced, not the error contribution from the component tolerance.

The interesting statistic would be the error in nominal voltage for the "most awkward division ratio". Look for that one!

Jean

Reply to
jean.easter

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If that\'s what he meant, then that\'s what he should have said, no?
Reply to
John Fields

I would use an 18k and a 22k and get 0% deviation or maybe a 2.2k and a 3.3k and get also 0% or a 8.2k and a 10k and get 0.1% all much better than your 480000 combinations. And there are 98 combinations already in the E96 series , that give you better than 0.5% How is that possible? Seem to be utter crap. Hint: I use a program called Rescad by Terry Harris

1996
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ciao Ban
Apricale, Italy
Reply to
Ban

"Ban" wrote in news:Gz86g.19641$ snipped-for-privacy@news.edisontel.com:

Works great!

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Thanks, Ban

Mike Monett

Reply to
Mike Monett

Newer version here

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Reply to
nospam

nospam wrote in news: snipped-for-privacy@4ax.com:

Thanks. Adding the E192 values is a good idea, but I'm not so sure about mixing different resistor tolerances. For example, what's the point in paralleling 5% and 0.1% resistors? If they are approximately equal, the 5% tolerance and drift characteristics would dominate, so you would get a very fine adjustment of a lousy resistor:)

Mike Monett

Reply to
Mike Monett

Silly question... is the usage of "E24" for 5% resistors, E96 for 1%, etc. common in Europe? It doesn't seem very common in the U.S., as far as I'm aware.

Nice table listing the standard EIA values:

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. I like the commentary about how E3, 50% resistor values are "no longer used!" I never knew such "bad" resistors were made... although I suppose that these days you could probably find IC processes where tolerances were that bad (but with excellent ratios, of coursE).

Reply to
Joel Kolstad

The mixing is entirely optional.

There is little point, but the E24 range is available in 1% and 0.1% and E96 in 1% also. I quickly checked digikey and found one line of 0.05% resistor only available in E24 for example.

There is no reason to exclude combinations of E24 and E96 or even E192 if you can get them with the same tolerance (and you can).

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Reply to
nospam

should be 2.7k

Reply to
Rodger Rosenbaum

The older version has at least two bugs that I noticed while doing the 5 volt to 2.75 volt divider example. The desired divider ratio is .55 and if you run the older version of ResCAD and select E96, the first result line says that you can get .11% error with 6.93k and 8.45k resistors. The problem with this is that 6.93k is not an E96 value.

The second error is that the older version misses the .39%, 5.76k, 6.98k combination, which is found by the newer version.

There may be more errors, but I noticed these two right away, and stopped looking.

Stick with the new version.

Reply to
Rodger Rosenbaum

Well, the E3 values are still used, just in 5% parts., and are certainly more commonly used than say E24 values.

In other words, I see a lot more 10K resistors than I see 9.1K's or

11K's. There's still a wide preference to use E6 values where exact selection simply doesn't matter at all in the design.

There probably aren't any manufacturers of 10% or 20% resistors anymore (well, actually if you tried hard enough you could find somebody selling them in carbon composition at 100 times the price of a carbon film), yet E12 values are much more commonly seen than E24-but-not-E12 values.

Similarly it's a lot easier to find 0.01% resistors if you will take them in standard E24 or E96 values. (There are a couple of octave-related and decade-related precision series that are extremely more common, too.)

Power resistors (esp wirewounds) still are sold as 25 ohms and 50 ohms even though they aren't E-series values. Long tradition I guess.

Tim.

Reply to
Tim Shoppa

Hi, The resistor pair solutions, for 5.00v/2.75v, mentioned are for 5% and 0.1% values. Interesting that these exist while there are no perfect 1% value resistor pairs.

The best 1% solutions are 1.33K/1.62K with -0.15% error and 1.15K/1.40K with

-0.17% error.

Now - if you wanted the best pairs, for slight buffer loading, BestPair III shows you several choices. The best is 1.37K/1.69K with a whopping +0.42% error.

Regarding another post - BestPair III does not mix resistor value families. Each family is on a separate tabbed page so it is easy to compare choices.

And yes I do know that the best pair errors are only nominal. You cannot get

0.15% precision with 15 resistors.

Cheers, Tim

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Reply to
Tim

Easy - if I understand the question.

For 1% resistor values, The resistor value pair with the largest ratio difference between it and its closest ratio neighbor is 115/113 whose closest ratio neighbor is all equal value pairs (i.e. ratio = 1).

Good for Geek Trivia?

Cheers, Tim

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Reply to
Tim

when parallelling a 330K 5% and a 100R 0.1% the 0.1% error is going to dominate.

Bye. Jasen

Reply to
Jasen Betts

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