Re: Homemade Voltage Divider

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Sean Taylor <sstaylor@xxxxxxxx>

>Original poster: Steve Ward <steve.ward@xxxxxxxxx>
>
>Hi Dave,
>
>Having built my own quarter shrinker and power supply, i will
tell you
>about what i did.
>
>For measurement i used a resistive divider.  Most meters have
a 10M
>impedance as standard.  Make a 1:100 divider with the 10meg
being the
>"1" and the 1G being the "100" (really its 1G-10Meg, but this
is close
>enough).

Snip...

Bad idea, Steve.  You always want a load resistor IN the
divider network so you don't accidentally leave the thing open
circuit.  I'd use a 1 GOhm resistor for the input (As you
satated) and a 1MOhm resistor for the load resistor.  Often
times (at least on a few meters I've played with), the 10 MOhm
input impedance was closer to 20 MOhms, that'll really throw
of your accuracy.  The 1 MOhm resistor gives you much more
predictable results, not to mention a good 1000:1 divider
ratio.  Another good thing: you can calibrate the system a bit
by putting resistors in series/parallel with the load
resistor.

Sean Taylor
Urbana, IL