Both were Chrony's but different ages.
Well, anything that happens must be possible. And now we have another example of one of the older Shooting Chronys going bananas. Hmmmm......
The fundamental system is extremely basic: A start pulse, a stop pulse, a count of the clock pulses in between, and a distance divided by measured time to get speed. Such a system either works right, or not at all. The only guess I can come up with is loss of hermetic seal on the oscillator unit, or some kind of internal contamination that slowly diffuses. I've never actually seen that happen.
So I am perplexed.[/quote]
Denton,
My first Shooting Chrony performed well, as far as I could confirm from shooting various loads (including the .22 rimfire used to test my first chronograph), and it was one of the early ones with cardboard "shades," as I mentioned previously purchased in the early 1990s.
Unfortunately it met its end around a decade later due to a misplaced .41 Magnum bullet. The two I had after that were the later models--which were the ones that declined in accuracy.
One of the things I learned from the Shooting Chrony folks during this period is that dust on the photo-sensors can cause problems, filtering in throgh the slots. Which is why I've placed transparent tape over the slots of every photo-electronic chronographs I've used since, including my Oehler. Tested that by, again, shooting the same ammo from the same rifle over the same chronograph. They all recorded the same velocities.[/quote]
Thanks for the additional information.
Dust in the optical system sounds plausible. Another might be that the designer saved about $.40 per unit by using an inductor/capacitor oscillator rather than a crystal oscillator. You can get away with that at 4 MHz, where some models ran their clock, but not very well at 12 MHz where my particular model had its clock. But, like you, I sent my Shooting Chrony to a younger shooter and moved on to a newer design.
I suppose that I will die wondering....
