Quote from: mondrasek on July 23, 2011, 12:08:44 PM
[snip]Every time I touch either DMM lead to the circuit in order to set up for a reading I will immediately notice an RPM change (audibly).[\snip]

if your dmm is powered via ac power source you may consider running it through a 1:1 isolation transformer.

take care.

nap

Quote from: slapper on July 23, 2011, 12:21:31 PM
if your dmm is powered via ac power source you may consider running it through a 1:1 isolation transformer.

Unfortunately it is a 9V battery powered device.  Thanks for the input.

M.

damn.
short of running the voltage reading though some sort of high impedance op amp circuit, ya got me.
don't take much though.

do you have model information on your dmm.

thinking your leads/probes may need some attention.

thanks.

nap

It's a Mastech MS8201H.  I appreciate the help, nap.

M.

Hi Mo . Here is something quick and dirty to try . Get a small cap say 0.1 microfarad . connect one side to The negative power rail and connect the other side to various parts of your circuit . As you connect it to each point in turn , check if the unwanted effect is still there . If this does not work , connect to an earth connection instead of negative rail and repeat tests . If this still does not work , repeat all tests with a 0.01 cap . Let us know if you get results .