<VV> Tachometer
Dennis & Debbie PLEAU
ddpleau at msn.com
Thu Mar 1 22:33:33 EST 2007
I've got 3 dwell tachs, all analog and all give a slightly different
reading. I like the control of the local utility over the frequency. I
should use them to calibrate my test equipment, but it would still be an
intermediate step to calibrating the tach and every step introduces error.
dp
>From: "Secular" <rusecular at yahoo.com>
>Reply-To: Secular <rusecular at yahoo.com>
>To: <VirtualVairs at corvair.org>
>Subject: Re: <VV> Tachometer
>Date: Thu, 1 Mar 2007 21:54:51 -0500
>
>
> 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
> >
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