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Re: Panel Meter Question

Original poster: "Scott Hanson" <huil888@xxxxxxxxxxxx>

Adam -

Make sure that the meter is not calibrated for 400 Hz.

I previously encountered some strange non-linear readings with some old
surplus Weston and Simpson AC voltmeters; when I looked more closely, the
faceplate was marked (in tiny lettering) "400 cycles".

Scott
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, October 01, 2005 9:30 PM
Subject: Panel Meter Question


> Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>
>
> I have a Weston 7544 panel meter that I bought used.
> It that reads from 0 to 300 VAC. It came with two 22k
> resistors in series with one of the leads, located in
> a small compartment. One of them is blown. The other
> reads 22.36k on my Fluke DMM. I went to my resistor
> drawer and found one that also reads 22.36k. When I
> place it in series with the good resistor, the meter
> reads too low across the scale. At 100VAC, it reads
> 90, and at 279 it reads 273. So I hooked it straight
> up to a variac without any resistors, and measured the
> input voltage and meter readings from 100 to 300. I
> figured I could simply find the ratio and calculate a
> better fit for a resistor. The problem is that it's
> not linear. It ranges from 21.86 volts input to read
> 100 volts, up to 59.1 volts to read 300 volts. I
> created a spreadsheet and played around a bit. If I
> pick a resistor value to make 300 volts correct, I'm
> 10 volts too low at 100. If I correct at 100, I'm 35
> volts too high at 300. Is there a better way to do
> this, or should I pick an average value, and call it
> close enough?
>
> thanks
> Adam
>
>