19 Jun
2011
19 Jun
'11
3:06 p.m.
On 19/06/2011 20:20, Tony Duell wrote:
What does it use as the frequency reference? Does it
use a crystal (and
if so, how does it handle the frequency change). What is the mark-space
ratio of the otuput (I found a narrow flash with a logner dark perid gave
a much clearier indication than a 1:1 ratio).
It uses a common crystal. You pick either a 3.2768MHz crystal for 50Hz
or a 3.93216MHz for 60Hz; it's assumed that you need one or the other
but not both (and generally that's true -- for checking motor speeds,
you use the appropriate strobe pattern).
It has an 8:1 duty cycle. As you say, you want a short flash.
--
Pete Peter Turnbull
Network Manager
University of York