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From: Tony Limson on 8 Sep 2005 09:25
(a) Imagine an 5-100kg (we do not know exact weight) object is hanged with a
piece of string/rope/wire and swings randomly.
(b) We do not have access to either end of this string.
(c) How can we measure, electronically,em the stress/tension on the string?



From: larwe on 8 Sep 2005 09:12

> (c) How can we measure, electronically,em the stress/tension on the string?

Study catenary curves. Apply some high school physics and algebra.

From: John Devereux on 8 Sep 2005 09:13
"Tony Limson" <tl(a)abcde.com> writes:

> (a) Imagine an 5-100kg (we do not know exact weight) object is hanged with a
> piece of string/rope/wire and swings randomly.
> (b) We do not have access to either end of this string.
> (c) How can we measure, electronically,em the stress/tension on the string?

I think you need to say if you are allowed to cut the rope in order to
insert a transducer (load cell etc).

Also the question appears a bit homework-like! So if it isn't, perhaps
you should tell us a bit more about the application so that people are
not put off replying.


--

John Devereux
From: Hans-Bernhard Broeker on 8 Sep 2005 09:14
In comp.arch.embedded Tony Limson <tl(a)abcde.com> wrote:

> (b) We do not have access to either end of this string.
> (c) How can we measure, electronically,em the stress/tension on the string?

Without access to the string, it can't be done in any way that could
justifiably be called "electronically". You're talking about doing
some serious physics here. Like: shoot a lot of x-ray intensity at it
and have an expert interpret the diffraction pattern for you to
determine the lattice length of the string, from that (assuming you at
least know the material) the deformation and from that, in turn, the
tension. Or shoot acoustic energy at it over a wide spectrum and try
to find its resonance frequency.

--
Hans-Bernhard Broeker (broeker(a)physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.
From: Robert Scott on 8 Sep 2005 08:17
On Thu, 8 Sep 2005 23:25:13 +1000, "Tony Limson" <tl(a)abcde.com> wrote:

>(a) Imagine an 5-100kg (we do not know exact weight) object is hanged with a
>piece of string/rope/wire and swings randomly.
>(b) We do not have access to either end of this string.
>(c) How can we measure, electronically,em the stress/tension on the string?
>

Without breaking the string, you can insert an in-line tension sensor
composed of three pulleys. The middle pulley is supported by a force
sensor. By knowing the angle of deflection of the string and the
force on the sensor, you can calculate the tension in the string.


-Robert Scott
Ypsilanti, Michigan
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