<VV> Tachometer

[Secular]

  Why is this discussion missing the use of a dwell/rpm meter? 
  Why can't all this "chime my bell" not get substituted by an 
  Dwell/RPM meter - then making the adjustment on the tach 
  based on what the meter is showing?

  hmmmm....

  Tony I. 

  
----- Original Message ----- 
From: "James Davis" <jld at wk.net>
To: <VirtualVairs at corvair.org>
Sent: Thursday, March 01, 2007 9:33 PM
Subject: Re: <VV> Tachometer


> This discussion is on how to adjust a working tach; not how to repair 
> a tach.  A signal generator would be ideal but Tony, Lew, Fred, and 
> Rad are probably the only Corvair people that have one.  Most of us 
> have AC electricity near when working on Corvairs.  Since power 
> companies spend millions keeping the frequency of AC perfectly stable 
> at 60 hz (cycles per second to you old ee's), why not use that 
> standard to calibrate the tach.  The tach wire in the coil is a handy 
> place to insert the frequency standard.  The problem is the tach is 
> looking for a 6 to 15 volt pulsed DC signal and the house current is 
> 117 volts, sine wave, AC.  Fortunately the tach has a zener diode in 
> the input which can change a sine wave AC to pulsed DC, so we just 
> need to drop the household voltage to the tach voltage.  A door bell 
> transformer changes 117 AC to 14 volts AC so it will work.  The 
> proper sized resistor in the probe will also work.  As for why 1,200 
> rpm?  Household voltage is 60 hz or cycles/sec.  That equates to 
> 3,600 cycles/min.  Since the there are three sparks per crank 
> revolution, divide 3 into 3,600 sparks to get (tada) 1,200 rpm ;-).
> Jim Davis
> 
> 
> 
> 
> 
> At 06:13 PM 3/1/2007, Mike Demeter wrote:
>>I do have a tachometer that does not work.
>>
>>Explain the doorbell transformer?
>>Explain the 60 hertz?
>>
>>Am I confused???
>>
>>Mike
>