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Steve,
It is static charge on the meter face plastic. Seen this before as I
worked in a calibration lab at Lockheed for 38 years. We always had a
spray bottle that cleaned meters plastic faces and also removed the
static charge. We also had kits to replace the meter movements and
techniques to balance the meter reading so the needle was the same
reading with the meter placed horizontal on its back versus vertical
standing up. Had a lot of experience with Simpson and other analog
meters decades ago. Simpson made some good meters and this was before
digital readout devices were widely used, portable, or affordable.
Note when mounting meters in metal panels in some cases the type of
metal can affect the meter accuracy. Best to calibrate or check the
meter accuracy while mounting in the panel if concerned.
If you get any iron fillings in the meter movement core that with give
erroneous reading also. But the key to the static problem as I see it is
that you say the meter tracked your fingers. Even wet saliva smeared on
the meter plastic face, although not preferred, should show a change and
help this problem .
Looked with Google search and there are anti-static spray products but
did not find the one we used to use. Sorry I no longer recall the name
of the product.
Terry Leonard
On 5/9/2018 9:17 PM, Steve White wrote:
In the control cabinet for my SGTC I have a Simpson 0 - 300 volts AC Wide-View iron vane voltmeter measuring the voltage from the wall. I briefly powered up the cabinet for a few seconds to check some things and then switched it off. Then, with all power off, I placed my finger over the indicator pointer of the voltmeter and its movement tracked my finger movement through the clear plastic cover! After this strange behavior, the pointer settled at a position substantially above the zero voltage point. It settled at about 30 volts with no power applied. I noticed that as time went by, the pointer gradually settled back to its true zero voltage point. This took about 10 minutes. I have PFC capacitors but I had them switched out at the time. The only other energy storage components that I can think of are the capacitors in the EMI line filter bricks. I don't think it could be static electricity because I tried discharging my body and the pointer still followed my finger. None of
the other voltmeters and ammeters in the control cabinet display this strange behavior. Does anyone know what is going on here?
Steve
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