i see , i suggest you do search for "Fuel injector " in the forum . i remember seeing some posts about them , this might help you , but as i know nothing about the signal of the injectors or how they are supposed to be , what you would monitor ? the absent of the pulse ? the width or what ? is it a PWM or just pulses ?
Thanks , but i want to use continuous signal so i can triger optocoupler , thats why i will search for peak hold circuit .If you can send me one that will be great.
ok , check this link . the fourth circuit is peak detector and hold **broken link removed**
just out of curiosity , you want to trigger optocoupler while the pulses are ok or while when they are gone ?
i think the previous circuit can generate an inverted logic (as long as the pulses are ok , the output will be high , and will drop to zero in the event of missing pulse by replacing the PNP transistor with NPN one )
hope this helps
Regards