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Re: Frequecy counter, measuring 2ndary output
Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>
One of the optical tachometers designed for measuring model airplane engine
speeds might work nicely for this. 6000 RPM = 200 Hz with a 2 blade prop.
There ARE such things as pulsed RF counters, and while an oscilloscope
might be a better way to measure a TC, if you have access to a fancy
counter (or one where the gate can be triggered off the power line, for
instance). Even an old HP 5325 could probably be pressed into service...
Feed a LV 60 Hz AC signal into one input to use as a trigger for the gate,
set the gate time appropriately... Or measure period...
All that aside, probably the cheapest way is to get the $50 ProbeScope
(220-0310) from Radio Shack (if they still have them). For measuring
frequency and generalized measurements, you aren't looking for phenomenal
accuracy and the limited resolution (8 bits I think) and capture length
(256 or 512, or maybe even bigger) might fill the need quite nicely.
> I would think it would be easy to make a hand-held device, using
> a photocell and a self-designed counter circuit to count the light pulses
> from the spark gap to measure the bps. A low pass filter would
> be used so the RF or notches are ignored. THe device would
> count for a given amount of time such as 1 second, and would
> read out how many firings occured during that time on an LED
> 7 segment display. I've always been meaning to build one, but
> never got around to it. There would be a sensitivity and reset
> button, etc. All built into a small metal box with battery power.
> I was also thinking of making a similar device to measure quench
> times. The firing of the gap would start the clock, etc.
> John Freau