23-02-2017, 06:02 PM
(This post was last modified: 23-02-2017, 06:03 PM by ppppenguin.)
(23-02-2017, 01:58 PM)Craig Wrote: Just checked three different Fluke DVM's against each other (ohms range on one to measure the input R of the voltage range of another. They were all between 10.12M and 11.22M.
This suggests that you shouldn't rely on the 10M input resistance of a DMM as part of a voltage divider. My own EHT probe was designed to work with the 50uA range of an analogue multimeter, giving 25kV FSD. It works equally well with a DMM though I have to divide the uA reading by 2 to get the voltage in kV. If I was starting again I'd make a 1000M probe rather than 500M.
Some inexpensive DMMs have a 1M input resistance. Best avoided altogether.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
