addition, an experimental ice motion detector
bridge on the upper St. John River. Each sensor
was installed at the USGS stream gaging station
consisted of two pairs of electrical wires. Each
at Nine Mile reach on the upper St. John to see if
pair, of different length, is joined at one end by a
such an early warning system could assist the
waterproof connection and at the other end is
existing forecast models used by the National
connected to a series of resistors, which in turn
Weather Service and the New Brunswick Fore-
are connected to the USGS Nine Mile stream
cast Center. This simple apparatus, described
gaging station's Data Collection Platform (DCP).
below, successfully transmitted the exact time of
An electrical diagram for the system is shown in
the first ice movement at the Nine Mile reach.
Figure 3. The voltage measured by the DCP de-
termines if both pairs of wires are intact, if one
or the other pair has broken, or if both pairs
ICE MOTION DETECTOR
have broken.
On 2426 February 1992, two experimental ice
A 4- to 6-in. deep groove was cut into the ice
motion detectors were installed at Nine Mile
cover from the bank perpendicular to the river
flow. Both pairs of wires were laid into the
groove and covered with packed snow and ice
chips (Fig. 4). One pair extended 100 ft outward,
Black
4.7 kΩ
Green
White
2.2 kΩ
Red
T 1 (J 1)
White
20 0-5 Volt Input
Red
2.2 kΩ
T 2 (J 2)
Connected to
Red
Met Board
16 SWD 5 Volts
White
14 0-5 Volt Input
Black
12 Common Ground
Black
Red
4.7 kΩ
White
Green
Handar 570A DCP
2.2 kΩ
Black
Figure 3. Ice motion detector.
2.2 kΩ
Figure 4. Installation of ice motion detec-
tor at Nine Mile, St. John River, Maine.
8
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