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

T

Tim

Jan 1, 1970
0
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 -->

http://www.velotec.com/BestPair.htm

Thanks for looking.

Cheers,
Tim
www.velotec.com
 
J

John Fields

Jan 1, 1970
0
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!!

---
If you do this:

+5.00 E1
|
[10k0] R1
|
+-----> E2
|
[10k0] R2
|
GND

Then:

E1R2
E2 = ---------
R1 + R2

Using 1% resistors, R1 could be 10100 kohms and R2 could be 9900
ohms, so if that were the case, E2 would be:


E1R2 5.00V * 9900R
E2 = --------- = ---------------- = 2.475V
R1 + R2 10100R + 9900R


Which is an error of -0.025V out of 2.5V, an error of -1%.

The same would be true, with opposite sign, if R1 was 9900 ohms and
R2 was 10100 ohms, so how do you propose to be able to come within
0.15% of the voltage divider's desired output voltage using a pair
of 1% resistors?

For that matter, how do you propose to get to 0.5%?
 
A

Abstract Dissonance

Jan 1, 1970
0
John Fields said:
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!!

---
If you do this:

+5.00 E1
|
[10k0] R1
|
+-----> E2
|
[10k0] R2
|
GND

Then:

E1R2
E2 = ---------
R1 + R2

Using 1% resistors, R1 could be 10100 kohms and R2 could be 9900
ohms, so if that were the case, E2 would be:


E1R2 5.00V * 9900R
E2 = --------- = ---------------- = 2.475V
R1 + R2 10100R + 9900R


Which is an error of -0.025V out of 2.5V, an error of -1%.

The same would be true, with opposite sign, if R1 was 9900 ohms and
R2 was 10100 ohms, so how do you propose to be able to come within
0.15% of the voltage divider's desired output voltage using a pair
of 1% resistors?

For that matter, how do you propose to get to 0.5%?


Magic ofcourse!!!
 
J

jean.easter

Jan 1, 1970
0
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
 
J

John Fields

Jan 1, 1970
0
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.
 
B

Ban

Jan 1, 1970
0
Tim said:
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 -->

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
 
M

Mike Monett

Jan 1, 1970
0
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

Works great!

http://www.armory.com/~rstevew/Public/Software/ResCad.zip

Thanks, Ban

Mike Monett
 
M

Mike Monett

Jan 1, 1970
0

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
 
J

Joel Kolstad

Jan 1, 1970
0
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:
http://www.logwell.com/tech/components/resistor_values.html . 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).
 
N

nospam

Jan 1, 1970
0
Mike Monett said:
Thanks. Adding the E192 values is a good idea, but I'm not so sure about
mixing different resistor tolerances.

The mixing is entirely optional.
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:)

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).

--
 
R

Rodger Rosenbaum

Jan 1, 1970
0
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% should be 2.7k
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
 
R

Rodger Rosenbaum

Jan 1, 1970
0

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.
 
T

Tim Shoppa

Jan 1, 1970
0
Joel said:
Nice table listing the standard EIA values:
http://www.logwell.com/tech/components/resistor_values.html . 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).

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.
 
T

Tim

Jan 1, 1970
0
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
http://www.velotec.com/BestPair.htm
 
T

Tim

Jan 1, 1970
0
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
http://www.velotec.com/BestPair.htm
 
J

Jasen Betts

Jan 1, 1970
0
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:)

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

Bye.
Jasen
 
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