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Re: Panel Meter Question

Original poster: "S&JY" <youngsters@xxxxxxxxxxxxxxx>

Adam,

Welcome to the real world of imperfect analog meters.  There are three
approaches you can take:  1) Pick a resistor value that give you the most
accuracy in the middle of your range of interest (i.e. the range of voltages
will you be measuring most of the time),  2) take off the meter face, turn
it around, and make a new meter scale on the back, using your Fluke DMM to
mark the intervals (e.g. every 10 volts), or 3) Do number 1, and print out a
little conversion table so you can read your meter, look at the table & see
the corrected value.

You might consider getting one of the el-cheapo DMMs from Harbor Freight
(about $3 on sale) and just use it instead.  It may be off a few percent,
but at least the percent error is likely to be linear across the meter
range.

--Steve Y.
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, October 01, 2005 10:30 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
>
>
>
>
>