Measuring the REVs per minute

[mmarell]

Hi everybody

Me and a friend of mine (Bizzarrini) are working on digital REV counter/tachometer/dashboard for our Monsters (2x '94 Monster 900), but we ran into a little problem.

We heard that there's a connector that gives a 0..12 V Voltage depending on the number of RPMs...and we also found that connector.

The only thing is, if we measure the voltage with a multimeter...the reading doesn't make sense. It seems to be OK when the motor is idling but starts doing very strange things

if we touch the throttle.

Does anybody know what might be going wrong?

Thanks!

Milan

[Bizzarrini]

Yeah, I've got de DP revcounter on, and it's working fine, so we def got the right connector, but the voltage reading just doesn't make sense. Perhaps a current output? Or pulsed?

Any thoughts?

Cheers!

[ellingly]

Yeah, I've got de DP revcounter on, and it's working fine, so we def got the right connector, but the voltage reading just doesn't make sense. Perhaps a current output? Or pulsed?

Any thoughts?

Cheers!

As far as my particularly limited understanding of tachos goes, it is pulsed, pulsing whenever the coil is outputting a spark. Now, I thought some of the Monsters are wasted spark, i.e. it'll pulse every time the engine turns over, rather than every second time as you'd expect for a four stroke.

Have fun at any rate .

[ducpainter]

Carbed Monsters, like you have, do in fact pulse twice for every combustion cycle...a wasted spark

[Speeddog]

I'm not aware of a linear 0V-12V tacho output.
Doesn't mean it's not there...

I suspect you'll have to make do with the pulsed output.

[Capo]

I believe that the tach is derived from the crank rotation sensor that also provides the input to the ECU. Its a pulsed Hall effect system. Souldn't be a problem to program the tach to indicate 1 rpm for every 2 pulses. But you would need to check just how many pulses the crank generates in one rotation

[Speeddog]

AFAIK, all Duc carbie OEM ignitions are triggered by the flywheel, so you get one pulse per revolution.

[mmarell]

I'm not aware of a linear 0V-12V tacho output.
Doesn't mean it's not there...

I suspect you'll have to make do with the pulsed output.

I don't mind counting pulses, that's easy ... but is there a connector/ a wire/ anything which I can use as an input for the counter?

I doubt the one we're using now is suitable for this ...

[Jobu]

I don't mind counting pulses, that's easy ... but is there a connector/ a wire/ anything which I can use as an input for the counter?

I doubt the one we're using now is suitable for this ...

I am pretty sure I am getting my signal from one of the output wires from the ignition modules.  These tell the coils when to fire which would give you an RPM signal.

I use the Veypor VR2, so I'm not sure how the wiring differs from what you are using.  The VR2 has a filter setting and I had to set that pretty high to get a good, stable reading.  Could explain some the erratic voltage readings you are getting.

[ducpainter]

I am pretty sure I am getting my signal from one of the output wires from the ignition modules.  These tell the coils when to fire which would give you an RPM signal.

I use the Veypor VR2, so I'm not sure how the wiring differs from what you are using.  The VR2 has a filter setting and I had to set that pretty high to get a good, stable reading.  Could explain some the erratic voltage readings you are getting.

I'm using the signal from the box too.