[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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.

> Gary,
> 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