Remote Health Monitoring for Asset Management

the sensor is implemented in this project. The manufacturer does not recommend the use of
parasite power for temperatures over 100°C due to high leakage currents, and encourages the use
of the V DD pin for power connection in applications where the extra wire connection is possible.
Using parasite power makes operation much more difficult because the bus must always be held
high during any 1-Wire device function. This causes complications with the timing and voltage
requirements for reading the data.
For this project, it was decided to use a 3-wire connection to power and read the sensor. This
included a ground wire, a data wire and separate power wire. The arrangement was selected to
provide long-term durability and to simplify software development. Additionally, there was little
disadvantage to using three wires within the instrumentation cable. Developing this technology
allowed for a single cable containing three wires to be utilized as the only data acquisition cable,
greatly simplifying the system overall and providing improved reliability over a thermocouple
system that would require a large number of wire pairs.
One significant advantage of the 1-wire sensors is the low cost of the sensor. In small quantities,
the sensor cost ~$2.00 each, but when purchased in large numbers the cost decreases. The low
cost of the sensor makes it practical to envision a large number of sensors being implemented in
the field. Additionally, the sensors consume very little power, such that a large number of
sensors can be powered from a common battery for long periods of time. The low power
requirement of the sensor could enable the development of a battery or solar powered system for
final implementation of the technology.
Array Design and Manufacture
To implement these unique sensors within the instrumented pile designed for this project, it was
necessary to develop a system by which a multitude of sensors could be connected along a single
set of wires, and subsequently installed along the length of a pile. Initial testing utilized
individual wires to test the sensors and develop software necessary to read and store data. This
requires that the insulation of the wires be breached at each sensor location, and three solder
joints applied to connect the sensor to the wire. However, it became apparent that there were
several challenges to implementing this design in the field. The primary disadvantage stemmed
from the reliability of the wire connections. Attaching a loose wire to the pile, and expecting the
high number of individual solder joints to remain reliable over long time periods was unrealistic.
Therefore, an alternative to this configuration was sought.
A literature search and discussions with manufacturing experts illuminated an alternative to
using a three wire configuration. Printable circuit boards, widely used in a variety of electronic
devices, provided an alternative that would enable the sensors to be secured to a rigid polymer
backplane, and this rigid backplane can then be connected to a suitable housing for installation in
the stream bed. Three “trunk lines” printed onto the polymer backplane would improve the
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