How is Tach Time recorded?

[Baron62]

I have a stock Tach on my 85 Archer. What does it take to record one hour of tach time? Someone told me that the tach does not accumulate time until RPM passes 1700. I thought it would be designed such that when you have completed RPM target (say 2500) for one hour you would get one hour tach time.

Set me straight on how these things work

 

[EchoDelta]

 

[Ray93J]

 

[Baron62]

 

[MickYoumans]

 

[magman]

 

[philiplane]

 

[Baron62]

 

[jruhnke]

 

[kshaw]