Nigel calm down, will try to improve my inglish aswell ok
OK, you gave me the circuit, i made it like you said i only added 3 things.
1) the zener protection
2) the 100K pot instead of the 100K resistor
3) the 10K resistance to 5volt rail replaced by a 10K pot.
Sorry that i call it a comparator.
Its just because i saw how the device works and i thought it compared the VR sensor voltage to the - pin voltage (or to the + pin voltage).
I then programmed the pic to output to me the measured details.
The pic counts pulses during 125ms. and send them out to the pc by the serial port/pins.
I then adjusted my scope program (you remember the bar graphic picture??)
sow i could plot the signal (values) from the pic.
is the situation now more clear?
i will upload an attachment as soon the limit is some bit higher need 60Kb per file...
else i could mail you them?
i found out that a cap at the picpin to ground of 1uF will give lower readings (lower count values) but they where super stable!! exept when reaching low pulse frequency/low rpm/low wheel speed.
i found out that a 10uF isn't usefull because it made the signal crap....
i also found out that a 110K pulldown can be usefull but that you need to adjust the pot settings allot.
I did al this kind of tries to cure the "doubt signal the pic gets"
do you untherstand what i mean with doubt signal?? I call a Sinus wave wich has a high frequency and wich max voltage is 0,9 ==> portbit high
and lowest voltage is 0,7 ==> portbit low..
untherstand the problem??
the doubt signal comes when the wheel speed is low.
then the next other problem is the spikes wich i hope came from the fact that the sensor vibrates and generates some doubt full pulses!!
surely its not prof talk but hope you untherstand ok?
Tks
i'm going to try a pc scope (DIY job) if it don't works i will buy a decent one.