Re: [PSUBS-MAILIST] water present alarm

["Jens Laland" <laland@artematrix.org>]

David

I just came over a document called "A sensor for water detection in
aircraft adhesive bondlines" (see quoted summary below):

<BEGIN QUOTE>

A simple and low cost sensor for detecting the water ingress in the
adhesive bond line was designed.

A compressed polypyrrole (PPy) powder was embedded in an epoxy adhesive
sandwiched between two aluminium (2024) substrates.

Interactions between PPy and water resulted in a rapid increase in
resistivity. The DC resistivity increased more than 20 times the initial
value when the PPy was contacted by water.

The increase was consistent with AC impedance at low frequencies which
showed 10 times increase if one PPy disc (3 mm diameter) was embedded or
100 times increase if there were 3 PPy disc embedded when the cell was
immersed in a brine solution for approximately 1000 h.

The resistivity of compressed PPy embedded in the bondline was unchanged
after 2000 h ageing at 100 C.

This indicates a good thermal stability. An initial test indicated that
the inclusion of a single 5mm diameter PPy disc in a 25mm diameter bonded
joint did not significantly decrease the dry adhesive strength of the
adhesive joint.

These results indicate that the sensor could potentially meet the
requirements of a bond degradation sensor in terms of

(1) low cost (few cents for one PPy disc)
(2) sensitivity to water
(3) long-term stability
(4) ease of monitoring and
(5) sustaining the dry bond strength.

<END QUOTE>

The entire document can be downloaded here:

http://dspace.dsto.defence.gov.au/dspace/bitstream/1947/3293/1/DSTO-RR-0172%20PR.pdf

Best regards,
Jens Laland

**
** To all:
**
**    I am in need of a very simple water detection sensor for use within
** hydrophone enclosures now under development. This could be as simple as
** two wires in close proximity to each other and are going to be used to
** alarm me to the presence of water that has leaked into the hydrophones
** air resonance chamber.
**
**    Sensors of this type could be installed in various electronic
** enclosures and battery storage compartments and could be a great way to
** be notified of undesired leaks. A simple 9 volt dc battery and remote
** buzzer are all I'm looking for.
**
**    Got any ideas? what do you use?
**                                                                        
 ** David Bartsch





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