[align=center]Is the Tacho Accurate?[/align]
Actually... it's more appropriate to ask, how accurate is the tacho?
I was logging the RPM digitally while riding the CBR250RR, and I was surprised that after bouncing off the rev limiter that the very accurate digital record showed more than 1,000rpm less than what I reckon I saw on the tacho gauge!
So I grabbed a CBR250R instrument that I've got lying around, and decided to test just how accurate it was...
I powered the gauge up with a constant 12.5V supply, and drove the tacho input with a square wave from a frequency generator, with similar amplitudes to what the bike gives out. To get accurate/repeatable results, I turned the input signal off, then on again to prevent the needle from getting 'stuck' by moving too slowly.
The blue graph is the ideal, red is the actual.
The worst was probably at the data point where the input was 16,935rpm and the display showed 17,800.
The needle covers the ground between two RPM values fairly quickly, basically within 0.7 to 0.8 seconds, however the last 500rpm is relatively slow.
Other tachos might have a different response, but I thought it was interesting... well... for perhaps one or two of you