RPM signal electrical characteristics?

[slipnfall]

Hi folks, I'm starting to design a data-aquisition box for my '92 240sx.. I'm wondering if anyone knows the RPM signal characteristics; my o-scope is down right now and don't have a way of viewing it. I assume it is frequency dependant, and not duty-cycle? What is the average range of frequency, and at what amplitude?

Thanks, as long as I can get some general idea of what the signal is, I can work around it for now. Not having a working scope is like being down 1/2 a brain.

[slipnfall]

bump, anyone?

For example let's say the crank position sensor puts out a 100Hz square wave. The period of the signal would be 10mS. That would make the pulses per minute 0.000166666. How does this correspond 'X' RPM? The crank position sensor only gets triggered once per revolution, correct?

[corn322]

did you get your scope working yet?I'll quote you text from the FSM, it might help:

"The crankshaft position sensor... blah blah blah... has a rotor plate and a wave forming circut. The rotor plate has 360 slits for 1 degree signal and 4 slits for 180 degree signal. Light Emittin Diodes and photo diodes are built in the wave-forming circut.When the rotor plate passes between the LED and the photo diode, the slits in the rotor plate coninually cut the light being transmitted to the photo diode from the LED. This generates rough-shaped pulses wich are converted into on-off signals by the wave-forming circut, which are then sent to the ECM."

[erich]

Your best bet (since you know what you are doing around a soldering iron) is to use the Nissan Consult interface and let the ECU do all of the work for you.http://www.plmsdevelopments.com/consult_if.htmhas all of the info you should need.

[slipnfall]

That's certainly a possibility: I could gather record lots of info from a single serial interface. In fact I designed a circuit board, following PLMS's schematic.(below). My scope went out around that time, and I guess I'v just lost interest, since it's finished...

My thoughts were to make a cheap home-brew LM1-style wideband interface, with RPM reference. That way i could just buy the wideband O2, and use my own 'box'. I have a habbit of ripping designs/ideas to suit my own needs.

I posted this general tach question to a google group, and have gotten good feedback. This was based off a Toyota IIRC:100Hz CPS signal=100Pulses/sec=6000Pulses/min, and since the CPS is pulsed twice every crank rotation, that equates to 3000RPM.

Anyone know what ratio the distributor(and thus the CPS) is geared compared to the crank itself? Is it also 2:1?

Thanks,-Jamie

::edit:: typo ::edit::

[Q45tech]

Depending on engine: Nissan CAS will output a [coarse/rough timing] pulse every 90 degrees of rotation plus a [fine] 1 degree pulse 360 times per CAS rotation [0n Q45].

V8= 90 degree pulse V6= 120 degree pulseI4 = 180 degree pulse

The problem is that the 0 TDC pulse [less mechanical offset advance] will be 2-3-4 times wider than all the others........so ecu knows where to start.

Hard to generate this single triple wide pulse [beginning] with inexpensive pulse generator.

[slipnfall]

Hmm, I have a spare distributor here, maybe I'll tear into it tomorrow. I have a feeling the 240 isn't quite as sophisticated as the Q's: if I had to guess it's just a single hall-effect type pickup which outputs every turn of the distrubutor. This would mean one CPS pulse for every two turns of the crank?

And yeah to imitate the Q's output you would almost have to use an arbitrary function generator.