major wrote:

I am using a 12 V 20 amp lamp dimmer to control some LED lighting.
While my two DVM's show nearly equal input voltage to the dimmer, they
both read separate voltages on the output side. One is reading 9 V and
the other 4 V. I am trying to determine wattage output at various
dimmer settings. Why the different in voltage readings on two different
DVM's and how to remedy?
These dimmers MUST be pulse width modulated, othwerwise the heat production
would be huge. You can't expect a DVM to give accurate reading of a
pulsating source. Possibly some true-RMS meters may do a decent job of
averaging the result, but I would not trust such a reading without verifying
it with another instrument, like an oscilliscope.

Jon