On 7/15/16 5:25 PM, Bob Camp wrote:
Hi
You can do a pretty good job with a high speed photo diode. They are not cheap,
but
you can get fast ones if your Visa card is up to it.
The next layer will be that at the relatively low strike voltages normally
used, Nixie’s don’t
light up consistently. You either need to compensate for temperature and
ambient light / then
calibrate each segment or sense each one as it turns on. Either way … it’s a
major learning
experience just to get it into the microseconds range. You can get to
nanoseconds, but that
may or may not be possible with conventional Nixie’s.
Preionize the gas with a radioactive source. If it works for Krytrons,
it can work for Nixies. You could also use a pulsed ion source that
turns on slightly before the "top of the second" to irradiate and
prepare the Nixie.
A true time-nut won't let such thing stand in the way of perfection.
Once you have them turned on, you go back through something similar when you
turn them
off. It takes a bit of time for all the little gas molecules to go back to rest
state. The data I have seen
on that sort of thing suggests a “many microseconds” to millisecond decay
process depending
on the gas and how it was driven.
Turning an ionized gas off is always harder than turning it on. Perhaps
a tailbiter type circuit or a negative pulse generator?
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