i dont have a great deal of skill, but my dad is an electronics technician so i'd hope he would have the necessary skills. When you say the amount of error, error in what? the input, or the allowed error in the output?
If it is a variable output (which is what i want ideally) then the error shouldnt matter too much as long as its consistent I dont imagine there would be error in the input.
For some extra information there are, i think, 10 triggers per revolution so that would be a max of 70000 pulses per minute (at 7000rpm) giving a signal range of approx 170Hz (at idle) to 1600Hz (i hope Hz is correct, its a while since ive learnt electronics).