This happened a few weeks ago, but I just now thought maybe I should share. Or, most of you already know this(?) While diagnosing the charging system on my 40......still 6V and a generator I was getting very false readings on my digital volt meter. Trying that meter on another car showed it was working fine. I had to dust off an older*****og meter for accurate readings. Like I said, most may already know this, but since I rarely get 6V stuff in my shop........
The explanation I have heard is that a digital meter tries to follow the voltage, which is controlled by vibrating points that produce spikes averaged in with nothingness...the gauge can't possibly follow that mess, and so slides into a psychotic break. The*****og meter placidly scans continually over spike and over open and accepts the average that the rig is putting out, just like your battery does...
My dad wouldn't use anything but*****og, he said that electronics were effected by external noise too much to be accurate on anything that was not filtered. I would think that an old 6V system would be really noisy. Good info I will keep it in mind.
It would be interesting to put the 6V gennie output on a oscilloscope and see exactly what the wave form looks like. I run into similar problems with the day job in trying to instrument 2 stroke snowmobiles with battery-less EFI systems, talk about noisy voltage signals. The battery acts like a huge capacitor and absorbs a lot of the noise and spikes.
OT I know but when I was still working as an operating engineer I had an ultra modern centrifugal chiller. We had to install filters because the incoming electricity to our building was so dirty (noisy) that the electronics could not function.
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