# Number nine

A while back I wrote up how to make A Perfect Divider [1] which divides a voltage by 10, 100, 1,000 etc. using mostly very common resistors (100K, 10K, 1K etc.) with only two uncommon resistors to make a resistance divider that divides by decade increments. You are stuck with the resistance error of your resistors, but there is zero numeric error. One less thing for your error budget.

That kind of thinking got me to fooling around with other standard resistance values to see if I couldn't find other useful pairs. And I found one. A 9.09K resistor in parallel with a 909K resistor gives a 9K resistance. Exactly.

Of course if you are going to do a divider string with multiple ratios, the first method is the best. It uses fewer resistors. But if you are just doing a divide by 10, you now have two options.

M. Simon's e-mail can be found on the sidebar at Space-Time Productions [2].