At 11:02 AM 10/9/2006, Jim Jarvis wrote:
>I got to thinking about this problem, and commented
>to Denny, off-reflector.
>
>There's an aspect to this which we haven't considered:
>
>Tampering with the guys is a threat to personnel aloft.
>Should someone be seriously injured or killed, we'd be
>talking homocide. If it went undetected, and someone
>were injured or killed, Denny would hold personal liability.
>
>This sabotage is 'assault with intent',not vandalism.
>IMHO, I would report it as such, and post signs on the guys
>with that message.
>
>If it's hunters with too much time and alcohol on their
>hands, they need a wakeup call. If it's deliberate, it's
>even worse.
or kids out fooling around...
They may not realize the impact of what they're doing, thinking it's
only "oh, that guys tower will fall down" and not realizing the
maximum downside of what they think of as a prank is death, dismemberment, etc.
>I would also devise a low-voltage circuit to pass through
>all turnbuckles, such that no turnbuckle can be turned
>without breaking or disabling the circuit. Said dropout
>should trigger an alarm in the home, allowing time for
>police to be called. A PITA, to be sure, but of all the
>options, most likely the cheapest and most secure.
An interesting design problem.
I wonder if you passed a small AC current (so you don't cause
corrosion) through the guys and monitored the voltage (i.e. the
resistance) it would be useful. Certainly, you could do one of the
"touch sensor" schemes (although they're notoriously RF sensitive),
but false positives would be a problem.
There are also ways to monitor the tension in a cable, but they're
not cheap, at least in the forms I'm familar with, where they're
interested in precision. For a low precision application, though,
something like a strain gage on a bar in series with the guy might
work well. I modified a cheap electronic bathroom scale to feed a
computer this way.. You use one of those DATAQ $25 data acquisition
pods to measure the voltage. You might be able to just glue the
strain gage element to the turnbuckle housing.
The parts are all cheap, at least. Check out the Omega.Com catalog.
$55 for 10 gages.
http://www.omega.com/techref/pdf/Positioning_Strain_Gages.pdf
>n2ea
>
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