I thought you were drinking the PBR.
Cause there's no way you'll get pulse periods of 125 pico seconds (.000125uS). And you wouldn't be able to read them if you did.
With 4000 pulses per Mile ...
At 120 MPH, you'll get 480000 pulses per hour (4000 * 120)
8000 per minute. (480000 / 60)
133.3 per second (8000 / 60)
which is a pulse period of .0075 Seconds (1 / 133.3)
That's 7.5 mS per pulse.<hr>
However, let's go back and take a look at davewanna's question.
It's giving 1639 pulses per kilometer.
Moving at 5 KPH, you'll get 2.28 pulses per second (1639*5/60/60)
That's a pulse period of 0.439 seconds.
Now with Pulsin at 20mhz, the resolution is 0.000002 (2 uS).
The maximum count for Pulsin is 65535 for a total time of 0.131 seconds.
The Pulsin will have timed out long before it could measure the pulse.
If we take the longest pulse that Pulsin can read 0.131 sec.
It would be 7.6 pulses per second (1 / 0.131)
457 pulses per minute (7.6 * 60)
27466 pulses per hour (457 * 60)
Divide that by the pulses/km (27466 / 1639 = 16.75 kph).
Anything slower than that, and you cannot read it with Pulsin @ 20Mhz.
Whew,
I think that deserves a Corona.<hr>
ADDED:
But, since davewanna is running at 4 Mhz, the Pulsin resolution is .000010 (10 uS)
A "full count" for Pulsin would be 0.65535 sec. (65535 * .000010)
Or 1.5 pulses per second (1 / 0.65535)
91.5 per minute
5493 per hour
For a slowest speed reading of 3.35 KPH.
At this point, I have to think that the "61cm of travel per tailshaft revolution" may not be correct if you can't read anything below 21kph.
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