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Portable Electronic Glass Stength Tester

Started by Unknown June 26, 2013
Spehro Pefhany wrote:
> > Michael A. Terrell wrote: > > > > Has anyone ever worked with 'Glass break detectors' for alarm > >systems? The old ones were tuned for the sound glass makes when it > >breaks, but some could detect the sound it makes before it shatters. > >The output was analog. I haven't worked with them for over 35 years, and > >don't remember the details. > > I just remember the ones that were made with foil..
That's late 1800s technology. Back when Ademco used brake drums for alarm bells.:)
In article <APidnfkuDIdgYlDMnZ2dnUVZ_rWdnZ2d@earthlink.com>, Michael A.
Terrell <mike.terrell@earthlink.net> wrote:

> Spehro Pefhany wrote: > > > > Michael A. Terrell wrote: > > > > > > Has anyone ever worked with 'Glass break detectors' for alarm > > >systems? The old ones were tuned for the sound glass makes when it > > >breaks, but some could detect the sound it makes before it shatters. > > >The output was analog. I haven't worked with them for over 35 years, and > > >don't remember the details. > > > > I just remember the ones that were made with foil.. > > > That's late 1800s technology. Back when Ademco used brake drums for > alarm bells.:)
I recall a vibration detector design from the 1970s that used a gold-plated ball bearing nesting in the cavity between three gold-plated brass screw heads arranged in an equilateral triangle. The vibration caused the ball to jiggle, breaking the circuit. The advantage of the ball was that its weight made it largely immune to low-frequency vibrations, as from passing trucks. The lower-cost variation was two horizontal rods passing through the center of a big washer, all gold plated. Vibration caused the washer to jiggle on the the rods. The advantage of such designs was that they could be part of a typical supervised-loop burglar alarm system, were dead simple, and were electronics-free. Joe Gwinn
Joe Gwinn wrote:
> > In article <APidnfkuDIdgYlDMnZ2dnUVZ_rWdnZ2d@earthlink.com>, Michael A. > Terrell <mike.terrell@earthlink.net> wrote: > > > Spehro Pefhany wrote: > > > > > > Michael A. Terrell wrote: > > > > > > > > Has anyone ever worked with 'Glass break detectors' for alarm > > > >systems? The old ones were tuned for the sound glass makes when it > > > >breaks, but some could detect the sound it makes before it shatters. > > > >The output was analog. I haven't worked with them for over 35 years, and > > > >don't remember the details. > > > > > > I just remember the ones that were made with foil.. > > > > > > That's late 1800s technology. Back when Ademco used brake drums for > > alarm bells.:) > > I recall a vibration detector design from the 1970s that used a > gold-plated ball bearing nesting in the cavity between three > gold-plated brass screw heads arranged in an equilateral triangle. The > vibration caused the ball to jiggle, breaking the circuit. > > The advantage of the ball was that its weight made it largely immune to > low-frequency vibrations, as from passing trucks. > > The lower-cost variation was two horizontal rods passing through the > center of a big washer, all gold plated. Vibration caused the washer > to jiggle on the the rods. > > The advantage of such designs was that they could be part of a typical > supervised-loop burglar alarm system, were dead simple, and were > electronics-free.
I saw all that stuff, back in the '70s when I helped a friend start an alarm business.
On Thu, 27 Jun 2013 18:27:55 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

> >>As far as some sort of accuracy... It's hail... can there be that much =
accuracy? =20
> >IEC 61215 10.17 comes from a committee of interested parties, that >probably have investments in companies that manufacture the required >test equipment. It is therefore to their benefit to make the accuracy >requirement as expensive as possible.
Typical standards comities are composed of vendors / manufacturers, end users, test equipment manufacturers, academics, and others with an economic interest (or compliance interest) in the outcome. Take LEED standards for an example: http://www.usgbc.org/leed I could just as easily selected ASTM, TIA, IEEE, NEMA, UL, or over a hundred others. ?-)