Voltage Divider Resistor Picker

Tim · Feb 17, 2006

Hi,
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 best pair!!

The Best Pair II 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.

BestPair has been upgraded to Best Pair II. 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

Rene Tschaggelar · Feb 17, 2006

Tim said:
Hi,
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?
[snip]

Save the 5$ and comparable software for free :

goto :
http://www.ibrtses.com/products/index.html
and download :
http://www.ibrtses.com/products/teiler22.zip

Rene

JeffM · Feb 17, 2006

The Best Pair II resistor calculator program will...

Tim

....then there's the old standby by Terry Harris at RSW's site
(Nearest; Series; Parallel; Divider):
http://72.14.207.104/search?q=cache....com/~rstevew/Public/Software/+zzz+ResCad.zip

nospam · Feb 17, 2006

JeffM said:
...then there's the old standby by Terry Harris at RSW's site
(Nearest; Series; Parallel; Divider):
http://72.14.207.104/search?q=cache....com/~rstevew/Public/Software/+zzz+ResCad.zip

Updated :-

"It now supports E192 range and supports selection from mixed ranges.
It no longer rounds input values to 3 significant digits. It can run
multiple instances (which is more a bug than a feature)."

at http://web.newsguy.com/pentangle/ResCAD20.zip

Tim · Feb 18, 2006

Yes - Please download and try the free program.

If you find you do not like it please take a closer look at BestPair II -->
http://www.velotec.com/BestPair.htm

In seven years BestPair I had ZERO unsatisfied users.

You get what you pay for.

Thanks for looking.

Cheers,
Tim
www.velotec.com

Rich Grise · Feb 18, 2006

Updated :-

"It now supports E192 range and supports selection from mixed ranges.
It no longer rounds input values to 3 significant digits. It can run
multiple instances (which is more a bug than a feature)."

at http://web.newsguy.com/pentangle/ResCAD20.zip

The number of times that I've had to select values from a range like
that, I've done it "by hand" with a spreadsheet. ;-)

Although, it would be kind of a fun programming project - maybe I'll put
up a "divider calculator" web page. ;-)

Cheers!
Rich

JeffM · Feb 18, 2006

maybe I'll put up a "divider calculator" web page. ;-)

Rich Grise

Like these?
http://www.google.com/search?q=resistor+divider+calculator

redbelly · Feb 18, 2006

Tim said:
Hi,
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 best pair!!

If they are 1% resistors, then NO pair will be within 0.15% !!!

Mark

Spehro Pefhany · Feb 18, 2006

If they are 1% resistors, then NO pair will be within 0.15% !!!

Mark

Typically 1% resistors are within 0.15% or so.

Nothing wrong with trying to get closer to the ideal values on analog
stuff.

Best regards,
Spehro Pefhany

The Phantom · Feb 18, 2006

If they are 1% resistors, then NO pair will be within 0.15% !!!

This isn't unqualifiedly true. Some pairs MAY be within 0.15%; some may not.
What you want to say is that there is no guarantee that any particular pair will
be within 0.15% when built with real 1% resistors.