High Tech, Inc. has recently developed a deep water passive marine hydrophone. The technology is based on a pressure compensation technique, developed by High Tech, that extends the depth capability of conventional flexural disc hydrophones. This product has been in development over the last few years and a patent recently applied for. This technology can be applied to both acoustic receivers and acoustic sources.
| HTI-99-PCFD1 | HTI-99-PCFD2 | |
|---|---|---|
| Sensitivity | ||
| dB re: 1V/uPa | -192 | -180 |
| Volts/Bar | 25 | 100 |
| Capacitance (uFarads) | 0.15 | 0.02 |
| Bandwidth | 0.01 Hz to 900 Hz | 0.01 Hz to 1800 Hz |
| Size (diameter X length) | 0.9 in. X 0.54 in. | 2.25 in. X 0.77 in. |
| (2.28 cm X 1.37 cm) | (5.72 cm X 1.96 cm) | |
| Operational Depth | 6000 meters | 6000 meters |
At this time prototype units have been assembled and tested at pressure in laboratory conditions. Future plans involve testing in boreholes with applications to crosswell tomography.
TVR of 98 Element Prototype
The HTI Digital Array System is designed for use in 3-D, 4-C, 4-D, and bottom cable surveys. The system operates in water depths up to 3000 m. The system can accommodate up to 64 channels at a sample rate of 2 msec. The total system consists of a vertical hydrophone cable anchored to the sea floor and connected by an S-tether to the autonomous recording buoy. The recording buoy communicates with the shipboard interface via radio telemetry.
Each of the nodes, or channels, in the digital vertical cable is made up of a hydrophone and a Delta-Sigma A/D converter electronics module. Nodes are interchangeable and designed to be easily replaced in the field.
An acoustic positioning system is integrated into each node. The spacing between nodes and overall cable length is determined by the user. Power consumption by each node has been minimized to facilitate power transmission down the cable from the buoy battery pack.
The buoy system electronics supplies all the power for the system. The buoy system battery can power the system continuously for up to 72 hours. The buoy electronics receives and executes commands from the shipboard control system and transmits QC data and status information back to the ship. The buoy can either record continuously or accept time break from a shipboard navigation system and record shot records.
Cable Node
converter ..................... 24 bit Delta-Sigma
instantaneous dynamic range ..................... >118 dB
total dynamic range ..................... >132 dB
converter input level ..................... +/- 4.5 V
low cut filter (-3 dB) ..................... 4 Hz, -12 dB/octave
high cut filter (-3 dB) ..................... 205.9 Hz
preamplifier gain ..................... selectable via downlink: 0, 12, 24, or
48 dB
channel gain matching ..................... +/- 1%
sample interval ..................... 2 milliseconds
total harmonic distortion ..................... -90 dB at -3 dB input
number of data channels ..................... 1 to 64
Environmental
operating temperature ..................... 0 degrees C to 40 degrees C
storage temperature ..................... -40 degrees C to 85 degrees C
shock (operating) ..................... 3 g @ 5 milliseconds, 2 g @ 11
milliseconds, 1 g @ 20 milliseconds
shock (non-operating) ..................... 40 g @ 30 milliseconds
humidity ..................... 5% to 95%, non-condensing
Buoy Electronics
record length ..................... 1 to 15 seconds
data recorder ..................... Exabyte 8505
tape capacity ..................... 5 Gbytes
data recorder interface ..................... SCSI
power supply ..................... rechargeable lead-acid gel cell pack
battery capacity ..................... 3000 watt-hours
battery life ..................... 72 hours record, 15 day standby
communication link ..................... VHF FM, 1200 baud receive, 9600
baud xmit
radio power ..................... 4 watts