DATA ACQUISITION EQUIPMENT 
U.S. GEOLOGICAL SURVEY
WOODS HOLE FIELD CENTER (WHFC)


Seismic Source and Receiver:

   Seismic Systems Inc. 15 In3 Water Gun

Benthos AQ-4 Hydrophone Streamer

Data Collection Platform:

  The DELPH2X system - Triton Elics International (TM)

Krontron IP Lite Windows 95 based Pentium machine
Saves water gun 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 EQUIPMENT

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 one or more dedicated boards supplied with: DELPH2X-AU32 in the basic package, and DELPH2X-MV32 as optional equipment.

The DELPH2X system has been designed in a modular fashion, enabling the acquisition of 1, 2, 6, 12 and up to 24 channels. The basic system includes a DELPH2X-AU32 board with 2 input channels. By adding the MV32 board, the number of channels can be increased by groups of six. A maximum of four MV32 boards can be linked to an AU32 board, giving a system 24 channels capacity.

ANALOG STAGE INPUTS OF THE AU32 BOARD

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.

ANALOG STAGE OUTPUTS OF THE AU32 BOARD

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.

SAMPLING OF THE AU32 BOARD

The sampling frequency is the same for inputs and outputs.

The sampling frequency is obtained by division of one of the base frequencies (48 kHz, 40 kHz, 32 kHz) by a factor ranging from 1 to 16

DIGITAL STAGE PROCESSOR

The AU32 board has a TMS320C31 (Texas Instruments) dedicated signal-processing processor with floating-point over 32-bit words. The clock frequency is 33 MHz, the processor base cycle is 60 nanoseconds, the computing power is 33 Mflops.
 

DIGITAL STAGE MEMORY

The AU32 board has 1 Mb, that is 256 kwords, of double access memory, without wait state, which is shared with the PC.

The memory can be expanded to 16 Mb with a daughter board.

DIGITAL STAGE INPUTS/OUTPUTS

The AU32 board has 4 logical inputs and 2 logical outputs at the TTL logic levels.

An external trigger input with programmable threshold is also available.

DIGITAL STAGE SERIAL LINK

The I/O bus of the TMS320C31 is available via an external cable. The serial link allows the linkage of several DELPH2X-AU32 boards or connection of external peripherals. The maximum possible throughput with the serial link is 8.33 Megabit/second.

DIGITAL STAGE PC INTERFACE

Communication with the PC is ensured by 8 registers placed in the input-output address space of the PC. The base address of the communications registers can be configured by micro-switches.

The DELPH2X-AU32 board is fitted in a PC/AT with an 16 bit ISA bus.

The PC can access all the TMS320C31 memory space; exchange between the two processors uses 16-bit words with an instantaneous throughput of 4Mb/s (depending on the PC type).

EXPANSIONS

Memory capacity can be expanded up to 16 Mb with a daughter board. Adding a daughter board does not require an extra slot.

A DELPH2X-MV32 expansion board with 6 extra synchronously sampled input channels can be connected to the AU32 board.

The analog characteristics of these 6 channels are identical to those of the DELPH2X-AU32 board.

A maximum of four MV32 boards can be connected, to obtain 26 input channels.

A dedicated clock board can be connected.


Return to  ALPH 98013 read-me  page

Return to  ALPH 98013 Index page