USGS
Equipment
Data Acquisition Equipment

Seismic Source and Receiver:


Geopulse Boomer Plate (left) mounted on Huntec Catamaran (right)

Specifications for the Geopulse Boomer Plate:
(for more information, see Geoacoustics Ltd.)

Source Level: 227 dB re 1ÁP @ 1m at 280 joules
Pulse Length: <0.2 msec
Max input Energy: 280 joules
Max input Voltage: 4kV
Weight: 12.5 kg
Dimensions: 38.3 cm (W) x 41.5 cm (D) x 4.3 cm (H)

Data Collection Platform:



The DELPH2X system
(for more information, see Triton Elics International)
Krontron IP Lite Windows 95 based Pentium machine
Saves boomer data via NFS network interface or on an Iomega Jaz subsystem
Current configuration will accept up to 2 channels of data asynchronously
Serial I/O ports (i.e., for navigation)
Parallel (Centronics) ports for printing on Oyo plotter
DELPH2X-AU32 board with 2 input channels using 16-bit Delta-Sigma converters


Overview of the system:

The DELPH2X system is based on signal acquisition and processing boards inserted in an IBM-PC-type computer operating under WINDOWS95 or WINDOWS NT. Acquisition and processing are carried out using the DELPH2X-AU32 dedicated board, with 2 input channels.

The AU32 board has two input channels in the 0-20 kHz frequency bandwidth with simultaneous sampling. The converters used are 16-bit Delta-Sigma converters with built-in anti-aliasing filters whose cutoff frequency follows the sampling frequency. The maximum input noise level is 3 ÁV rms between 100 Hz and 20 kHz. Distortion is 0.01%. The AU32 board has a full 70 dB amplification chain allowing input levels to be programmed from 1 millivolt 0-peak to 5 volt 0-peak at full scale. Input connecting cables are SMB subclick coaxial cables.

Each AU32 board has two independent output channels in the 0-20 kHz frequency band. The converters used are 16-bit Delta-Sigma converters with built-in anti-aliasing filters. A micro-switch for each channel, placed on the back panel, enables selection of the type of output, either 10 dBV maximum over 600 ohms, or 10 dBV maximum over 50 ohms.


Benthos AQ-4 Hydrophone Streamer
The hydrophone streamer array is comprised of an active section containing 10 elements spaced 0.3 meters (1 foot) apart and connected in a series. A preamplifier unit is inserted between the tow cable and the active elements. Total length of the unit is 4.6 meters (15 feet) with 7.6 meter (25 foot) rope tail.
Specifications for the Benthos AQ-4 Streamer:
(for more information, see Benthos Inc.)
Acoustic Sensitivity (dBV re 1 ÁPa ▒ 1dB): -201dB
Acceleration Sensitivity (dBV/G): -70dB A / -60dB T
Frequency Response (▒ 1.5dB): 1Hz -15Hz
Directivity (▒1dB on axis): 15kHz
Sensitivity vs. Depth (loss at 1,732 meters): 0.8dB
Depth (meter--rated/destruct): 3,300/6,600
Size (cm--diameter/length): 1.30/3.30
Weight (grams--air/water): 4.0/2.9
Capacitance--(pF ▒ 25%): 2,400