interesting tach thought..

[mrdjflores]

wonder what would happen if you hook a 10 pole tach to a 20 pole alternator???

if a 20 pole alternator spins 1000 times...you would have 20,000 pulses (every 20 pulses is one revolution) correct???

if you send these 20,000 pulses to a 10 pole tachometer...the tachometer would 'think' you are turning 2000 rpms (10 pulses per revolution)...correct ???

my thinking....take a 10 pole tach...remove the face...scan into computer...renumber the scanned image...and print out on vinyl label...take new label and stick it to the original tach face...then reassemble the tach

sounds like it should work...but have a feeling i'm missing something

your thoughts ??

 

[Silvertip]

Re: interesting tach thought..

You are missing something. That something is the tach was designed for a specific input frequency. Just because the tach can recognize and process 10,000 pulses @ 1000 rpm does not mean the tach can recognize and process 20,000 pulses. Electrical engineers don't work that way and electronics has its limits. What you also failed to recognize is that at some given rpm (using the 10 pole tach) the needle reaches the high end of the scale. Most tachs read 0 - 6000, 0-7000 or 0-8000 rpm. So lets say whatever engine you have has a redline of 6000 rpm. Your tach therefore reads 6000 rpm. So now if you double the input frequency (20 pole frequency) the needle would be pegged as it is trying to reach 12,000 rpm. Just changing the face plate accomplishes nothing.