Re: Identifying and Adapting Meters

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Paul B. Brodie" <pbbrodie@xxxxxxxxxxxxx>

Dave,
Thank you for all the really good advice, especially about determining the 
values of unknown meters. Yes, I would very much like the software you 
described. Can you please send me a copy or a link to a copy?

I knew the TCT output is AC and that I was going to have to rectify the 
output before sending it to the meter. I was hoping that since the output 
level has to be high enough to drive the bi-polar LED that it should be 
high enough to overcome the forward voltage drop of rectifier diodes. Since 
all I'm looking for is the meter to show the strength of the signal as I 
change the frequency so I can determine the frequency with the maximum 
output, I thought I could just use a Schottky diode as a simple half wave 
rectifier. I'm worried that cutting the signal in half might make it too 
low for my purpose.

With my extremely poor vision, I don't think I can properly determine the 
signal strength from the brightness off an LED. I'm going to finish the 
tuner and just start trying different ways to rectify the output and see 
what it does on the meter.

Thanks a bunch for your help.
Paul
Think Positive

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, May 18, 2005 6:54 PM
Subject: Re: Identifying and Adapting Meters

> Original poster: David Speck <Dave@xxxxxxxxxxxxxxxx>
>
> Paul.
> There's nothing at all stupid about recycling meters at all. I do it often.
>
> The meters are probably marked with a Plus sign on one terminal.  If not,
> the + terminal is probably the one that had the red, white or yellow,
> orange or brown wire on it (negative colors are usually black, blue,
> violet, or gray for American designed circuits).  If the unit came from
> Japan, then the white wire is probably the + lead, and any other color for
> the negative, but there is no absolute rule.
>
> If you have an adjustable DC power supply, just connect the supply with the
> proper polarity in series with a 10K resistor, your meter under test,  and
> an inexpensive digital volt meter set on the milliampere range.  Start with
> the supply at 0 volts, and increase the output slowly.  If the meter
> deflects backward, you have the polarity wrong.
> If it deflects forward, then advance the power till you have a full scale
> reading, and consult your handy DVM to see what the full scale current is.
> You may need to increase or decrease the test 10K resistor to get a full
> scale deflection.  If you have to apply lots of voltage to get even a
> little movement, then there is probably an internal scaling resistor inside
> the meter.  With careful disassembly, this can be removed, or, more simply,
> shorted out to get the max sensitivity from the meter movement.
> After you find out what current gives you a full scale deflection, you can
> apply your DVM across the meter terminals, adjust for a full scale
> deflection again with just the power supply and the temporary scaling
> resistor, and see the voltage drop across the meter.  Using R=I/E, you can
> then determine the internal resistance of the meter coil.  With these
> parameters, you can select a scaling resistor to make the meter display
> just about anything you want for a full scale reading.
>
> Having said that, and NOT having looked at the Tesla Tuner schematic in a
> while, IIRC, the tuner feeds AC to the LEDs, and relies on the human eye to
> integrate the pulses of light to balance the two LEDs' output.
> If that is correct, a DC meter won't help you.  You will have to build a
> simple precision rectifier (otherwise known as an absolute value circuit)
> with an op amp, a pair of diodes and a few resistors.  Circuits for these
> are easily found with a Google search.
> BTW, there's a really neat shareware program out there called MeterScale or
> something to that effect, that makes very nice custom meter faceplates with
> your choice of legend and graduations.  Definitely worth the $10.00
> registration fee, and makes a very professional looking replacement meter
> face of nearly any conceivable size, scale,and configuration..  I can
> forward you a copy or a link if you are interested.
>
> HTH,
> Dave Speck
>
>>I would like to use one of these to indicate the output level of the Tesla
>>Coil Tuner, in addition to or in place of the LED. Any help will, of
>>course, be greatly appreciated. I will even accept well intentioned
>>criticism about what a stupid idea this is!! Regards.
>>Paul
>>Think Positive
>
>
>