Re: good scopes for coiling

["Tesla list" <tesla@xxxxxxxxxx>]

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

Terry,
Thank you. That sounds like a good solution. I have been struggling trying 
to determine the output levels, volts and amps, because my DVM suddenly 
started acting up with all kinds of crazy readouts and just plain quitting. 
I think I damaged it while trying to monitor the voltage on my variac while 
driving an ignition coil with a dimmer. Even though I was using an EMI 
filter, the DVM went wild when the ignition coil fired. I believe the meter 
leads were acting like an antenna and picked up the radiated RF or 
something like this. I'm really upset because it is (was) a really nice 
meter that my wife gave me as an X-mas present. I was planning to use the 
built-in frequency counter to calibrate my tuner. It also has a transistor 
tester and capacitance meter. Maybe I can find one cheap on E-Bay. I had 
been saving to buy an oscilloscope and I guess that has to go on the back 
burner now.

I didn't realize just how dependant on the DVM I have become. I am way too 
lazy about not just getting out a piece of paper and a pencil, referencing 
the schematic, and using good ol' Ohms law!

Paul
Think Positive

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, May 19, 2005 12:58 AM
Subject: Re: good scopes for coiling

> Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Hi,
>
> Just use two normal LEDs in anti-parallel (like back to back).  Hook the
> meter in series with one of the LEDs which will rectify the current for you
> QED (quite easily done)...  It will be about 5mA of current so play with
> the meter shunts or whatever for about that level.  The voltage is 0 to 9
> volts.  There is a dropping resistor in series with the LEDs too that can
> be adjusted at will.
>
> Cheers,
>
>         Terry
>
>
> At 09:10 PM 5/18/2005, you wrote:
>>Malcolm,
>>Yes, my intent is to rectify the AC output and feed it to the meter. One
>>problem is that I don't have any idea what the output voltage is and
>>whether or not I might get dropouts, if the level drops lower than the
>>forward voltage drop of the diode(s). I am assuming that since the output
>>has to drive the LED, it is high enough.
>>
>>My problem is that trying to judge the output level by the relative
>>brightness of the bipolar LED is not a very good option for me because of
>>my extremely poor vision. I'm not sure that I will be able to do this at
>>all. I was hoping that I could use a very simple rectification because I'm
>>not looking for any particular accuracy. I just want to use the meter to
>>indicate the signal strength as it fluctuates so that I can find the
>>maximum point. If this is all I am doing, can I just use a Schottky diode
>>as a half-wave rectifier and feed this to the meter? The problem here is I
>>will compound any problem I might have with a low signal level, cutting it
>>in half with the rectifier. I think what I'll do now is just start trying
>>things. I have nearly completed the tuner itself. I only need to solder
>>the connections to the LED and I'm through. I will try the half wave
>>rectification with a Schottky diode first and see what I get and go from
>>there. Thanks.
>>Paul
>>Think Positive
>>
>>----- Original Message -----
>>From: "Tesla list" <tesla@xxxxxxxxxx>
>>To: <tesla@xxxxxxxxxx>
>>Sent: Wednesday, May 18, 2005 6:56 PM
>
>