[Farmall] Tachometer

tomehrkam at houston.rr.com tomehrkam at houston.rr.com
Mon Dec 20 14:52:50 PST 2004


I have one of those. There is a switch to configure it for the number of
blades on the prob. Mine has a setting for a two blade or three blade prop.

It works by looking at the reflection from the prop. The electronics count
the number of times the blade passes the lense and then calculates the
correct RPM based on the switch setting.

If you were to paint two white marks on the fly wheel or pully then it
should work just fine for reading tractor RPM. If you paint just one flag
then you would have to multiply the RPM reading by 2.

The only problem may be the contrast. You need enough of a signal for the
counting circuit to work. With a prop that is not much of a problem. It is
either there or not. A flywheel may have other reflections or holes that
the optical ckt could mistake for a flag.

I have used strobe lights to measure rpm. My company has one with a
calibrated dial. You illuminate the shaft/ pully etc with the strobe and
adjust the frequency so the shaft appears to stop. You can read the RPM off
the dial.




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