diesel tach signal vs. gasser tach signal... now w/ pictures

[Vincent Waldon]

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

[RabbitJockey]

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

[cal]

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

[Vincent Waldon]

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:

[cal]

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

[Vincent Waldon]

Because the diesel signal is not an exact multiple of the signal the gasser tach is expecting there's no simple way to do this... a microprocessor is required.

Unless you can design, build, and write assembly language for microprocessors the easiest solution is probably to buy an off-the-shelf converter from people who can:

http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=128/prd128.htm

[Smokey Eddy]

For those of us that can write assembly language for microprocessors have you tried this already? have you come up with anything vince?  :lol:

[zukgod1]

For those of us that can write assembly language for microprocessors have you tried this already? have you come up with anything vince?  :lol:

Oh look he's braggin!!

           

Just teasing ya smoke.

[79rabbit4dr]

http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=128/prd128.htm

bookmarked!!!

thanks for all the wisdom Vince!

[Smokey Eddy]

For those of us that can write assembly language for microprocessors have you tried this already? have you come up with anything vince?  :lol:

Oh look he's braggin!!

           

Just teasing ya smoke.

Haha! Just for the benefit of the forum Dan! And you  :wink: can call me Ed

bookmarked too  

[Vincent Waldon]

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:

[Smokey Eddy]

Hahahahahhah!
Nicceee!!!