2003-05-10
Fred Kennedy wrote noticing that my circuit diagram was inconsistent with the text. Indeed, he was correct. I've fixed the circuit diagram, the two 100 k resistors are in series not parallel. This gives a division of 0.000999 which is 1/1000 to three decimal places. This is accurate enough for my purposes and considering the resistor tolerances is probably very optimistic anyway.
Note also that if your meter is not a Hi-Z input (ie at least 10 M) then you should take its input impedance into account when you calculate the divider network. It was common to turn a VOM or bare D'arsonval movement into a HV meter by using only a series string of resistors.
2 comments.
Parent article: High Voltage Probes.