Here's the signal from the W terminal of a diesel alternator at about 1100 RPM:
Here's the signal from the coil of a gasser at about 800 RPM:
Not a perfect experiment because my diesel idles quite a bit faster than my gasser, but the idea is to show that the W signal is quite different both in amplitude *and* frequency.
The gasser tach signal is approximately 26 Hz with a peak voltage of around 80V, and the diesel tach signal is about 200 Hz with a peak voltage of around 10V.
Again, not exactly the same RPM.. but you get the idea... recalibration is in order if you want a gasser tach to work in a diesel. Or, a converter circuit that does the signal division.... looks like about a "divide by 8" would be a start. Same goes if you wanted to use a generic gasser cruise control that expects to be hooked to the coil.
BTW, since the signal from the W terminal is a square wave your multimeter on the "AC Volts" setting can detect it nicely:
If you had a multimeter with a "frequency" scale you could measure the signal directly.
Filed under "a picture is worth a thousand words",
Vince
oscilloscope oh my. i used to like playing with them at school, i was the only kid in my class that could get anything to come up on the screen haha, i didn't learn *** in that class, how horrible we never even got taught to use those i figured it out myself :roll: neat to see these, looks about right since a w terminal plugged into a gas tach says about 4k, and if u hit the gas it goes to 8 and then flutters all over the place haha
so with the right resistors etc you could build an in-line converter and not have to touch the gasser tach yes???
if so what do i need??
thanks in advance
Just resistors won't do the trick... you need to condition the signal *and* divide the frequency.
Or you can buy a signal converter.
Or you can recalibrate the resistors on the gasser tach.
Or you can install an optical pickup.
Or you can install a flywheel pickup.
Lotsa options... "search" is your friend in this case. :wink:
well i've read the convert your gasser tach thread like 15 times now, my problem is i've got a motometer tach that isn't listed on there and i can't seem to apply the principle to work out the values for mine.
how would you go about making a signal converter then? as i can't find them in the uk
For those of us that can write assembly language for microprocessors have you tried this already? have you come up with anything vince? :lol:
For those of us that can write assembly language for microprocessors have you tried this already? have you come up with anything vince? :lol:
As it happens, I have the honour of having written the *only* piece of code that was not Y2K-compliant at our local hospital back in the day... thousands of pieces of complicated medical equipment and the microprocessor-controlled neonatal transport incubator I helped build was the only thing that had a confused clock on Jan 1, 2000. Good times !
'Course back then we had it tough... no fancy "1"s and "0"s like folks have today... I had to write the whole thing with only "0"s. :wink:
