An eight-element oil-filled hydrophone array is
used to measure the acoustic field in littoral waters. This
prototype array was deployed during an experiment between
Jeffrey’s Ledge and the Stellwagen Bank region off the coast of
Rockport, Massachusetts USA. During the experiment, several
humpback whale vocalizations, distant ship tonals and high
frequency conventional echosounder pings were recorded.
Visual confirmation of humpback moving in bearing relative to
the array verifies the directional sensing from array
beamforming. During deployment, the array is towed at speeds
varying from 4-7 kts in water depths of roughly 100 m with
conditions at sea state 2 to 3. This array system consists of a
portable winch with array, tow cable and 3 water-resistant
boxes housing electronics. This system is deployed and operated
by 2 crew members onboard a 13 m commercial fishing vessel
during the experiment.
Non-acoustic sensor (NAS) information is obtained to
provide depth, temperature, and heading data using
commercial off the shelf (COTS) components utilizing
RS485/232 data communications. Acoustic data sampling was
performed at 8 kHz, 30 kHz and 100 kHz with near real-time
processing of data and enhanced Signal to Noise Ratio (SNR)
from beamforming. The electrical system components are
deployed with 3 stacked electronics boxes housing power, data
acquisition and data processing components in water resistant
compartments. A laptop computer with 8 TB of external storage
and an independent Global Positioning System (GPS) antenna
is used to run Passive Ocean Acoustic Waveguide Remote
Sensing (POAWRS) software providing beamformed
spectrogram data and live NAS data with capability of
capturing several days of data. The acquisition system consists
of Surface Mount Device (SMD) pre-amplifiers with filter to an
analog differential pair shipboard COTS acquisition system.
Pre-amplifiers are constructed using SMD technology where
components are pressure tolerant and potting is not necessary.
Potting of connectors, electronics and hydrophones via 3D
printed molding techniques will be discussed.
Array internal components are manufactured with
Thermoplastic Polyurethane (TPU) 3D printed material to
dampen array vibrations with forward and aft vibration
isolation modules (VIM). Polyurethane foam (PUF) used to
scatter breathing waves and dampen contact from wires inside
the array without attenuating high frequencies and allowing for
significant noise reduction. A single Tygon array section with a
length of 7.5 m and diameter of 38 mm contains 8 transducer
elements with a spacing of 75 cm (1 kHz design frequency). Pre-
amplifiers and NAS modules are affixed using Vectran and steel
wire rope positioned by swaged stops along the strength
member. The tow cable length is 100 m with a diameter of 22
mm that is potted to a hose adapter to break out 12 braided
copper wire twisted pair conductors and terminates the tow
cable Vectran braid.
This array in its current state of development is a low-cost
alternative to obtain quality acoustic data from a towed array
system. Used here for observation of whale vocalizations, this
type of array also has many applications in military sonar and
seismic surveying. Maintenance on the array can be performed
without the use of special facilities or equipment for dehosing
and conveniently uses castor oil as an environmentally safe
pressure compensating and coupling fluid. Array development
including selection of transducers, NAS modules, acoustic
acquisition system, array materials and method of construction
with results from several deployments will be discussed. We also
present beamformed spectrograms containing humpback whale
downsweep moans and underwater blowing (bubbles) sounds
associated with feeding on sand lance (Ammodytes dubius).
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Development of a 3D-printed force sensor with carbon paste
Force sensors play an important role in the biomedical devices industry, especially in motion- and pressure-related devices. Such sensors are designed to collect force or pressure data by converting it into electrical signals. The data can then be sent to and analyzed by a local or cloud-based processing unit. It is vital that the sensors can be fabricated in a way that time efficiency, cost efficiency, and quality are all maximized. The advent of three-dimensional (3D) printing has greatly facilitated prototyping and customized manufacturing, as compared to older crafting methods (such as welding and woodworking), 3D printing requires less skill and involves less costly materials making it much more time- and cost-efficient. Technological advancements have also improved the quality of the actual sensing materials used in sensor-based devices, and notably, carbon-based materials have become increasingly favored for use as sensing elements. In the presented sensor, the modern sensor fabrication methods of 3D printing and using carbon materials as sensing elements are combined.
The sensor presented as a proof of the above concepts is a cantilever flex sensor. The sensor consists of a 30 mm-long cantilever extending from a 2.5 mm-thick wall, with a second wall of the same thickness parallel to the cantilever. After designing this structure and printing it using a 3D printer, the top surface of the cantilever was coated with a thin layer of conductive carbon paste and two copper wires were stripped and soldered to a pair of copper alligator clips, to be used for testing purposes. To test the sensor, the two copper wires were clipped onto the sensor (Figure 1A) and each wire was connected to a multimeter probe on the end opposite of the alligator clip. Then, using a set of four through holes in the parallel wall (along with a slotted rod), the tip of the cantilever was pressed down to an angle of 5, 10, 15, or 20 degrees (Figures 1B, 1C, 1D, and 1E, respectively) below the original plane of the cantilever and held there for 2 minutes. The resistance between the ends of the cantilever was measured throughout each trial by the multimeter, and the results (Figure 1F) for each angle were compiled and analyzed to determine the effect of each depression angle on impedance change, and thus, the overall effectiveness of the sensor. In the future, a notable improvement would be miniaturizing the sensor to facilitate in integration of the sensor in wearable and biomedical devices.
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- Award ID(s):
- 1827173
- NSF-PAR ID:
- 10124515
- Date Published:
- Journal Name:
- 236th Electrochemical Society Meeting Abstracts
- ISSN:
- 2151-2043
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
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