Re: 4 stroke engine Rpm sensor

[William Gilbert]

Frequency to voltage into an analog input might be a good approach. 
There are F/V converter chips availiable, and quite a few off the shelf 
products as well, i. e. Red Lion. Have used them before, but don't 
remember model#s. F/V gets you away from problems like point 
bounce(usually uses a monostable running into an integrator) and tends 
to disregard most of the noise that would drive a high speed counter 
input bonkers. Also, trying to use jittery Windows software timing to 
read a counter regularly isn't very reliable.

-BG

Brent DeWitt wrote:
There are a number of methods, but to find the easiest one, a little more
needs to be known about the ignition system of the engine.  If you want it
to work on just about any motor and be portable, then the clamp on style
current pickup from an inexpensive timing light could be made to work.  If
you can get to the primary side of the ignition coil easily, then just count
the 12 volt pulses and divide appropriately.  If it's a magneto ignition,
the inductive clamp is the only low voltage method.  Don't forget that you
have twice as many revolutions/min as you have sparks/min to a given
cylinder.
Brent DeWitt

-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Behalf Of Lucamax
Sent: Sunday, February 15, 2004 7:05 AM
To: Info-LabVIEW Mailing List
Subject: 4 stroke engine Rpm sensor
Hi all,
I need to acquire the RPM of a 4 stroke engine.
Either using  a digital input or an analog input of my acquisition board.
Some digital  tachometers <http://www.gpt.it/power_rpm%20eng.htm>use as
sensor just an electric cable with a clip connected to the spark plug wire.
Any idea how it can be done in such way ?
Thanks !





--

Bill Gilbert, EM Tech
UMN School of Physics and Astronomy
Tel   612 624 4870
Pager 612 622 0174
Fax   612 624 4578      
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