I think I know what you mean, and so I think I agree with you.
The example I remember was that a vamo was set at 14 watts and for the given ohm reading it should have been outputting X volts, however it was actually outputting less. I'm not sure if the vamo was saying it was outputting X and was actually outputting less or what the situations was. I'm not familiar with the vamo so I can't say what the deal was. Mike and BJ were talking about their self defense vamo's in another thread.
The Vamo meter is completely passive, it does not show anything under load. Here is a Vamo set at 14 watts 3.8v on the Batt. 28g 1.5 ohm coil. ECD meter has .1ohm internal. Advance by frames to see the readings on load. Clic pic for video.
