Aloha Proof Module Design

Cabled Observatory Presentation

School of Ocean and Earth Science and TechnologyFebruary 2006

Purpose

• Proof of Concept

• Long term testing of data communications capabilities.

• Prepare for full observatory phase 2 deployment:– Any modifications learn from phase 1– H4 cable cut and emplacement– Cable termination emplacement

Proof Module Overview

• The proof module has no supervisory command and control.

• The proof module monitors engineering status, data communications, and system operation.

• The proof module has no customers, but includes two internal instruments:– Wide amplitude and frequency range hydrophone– Digiquartz pressure sensor– Continuous pressure spectrum from DC to 40KHz

• The proof module has no time stamp capability, but timing will be accomplished at the shore station.

End Cap w/ DQ and HYD

Microcontroller Power Supply DigiquartzDQ (under) .

Hydrophone ADC Manchester

Top ViewManchester ADC Hydrophone

Microcontroller& DQ Power Supply Digiquartz

Power Supply

• The proof module has a shunt regulator- based power supply consisting of three sections:

– Linear Shunt Regulator

– DC/DC converters

– Filtering

Shut Regulator Section

• Input power to the shunt regulator is 12 VDC at 1.6 amps (20 watts).

• This provides the input voltage to the DC/DC converters.

• All power not used by the DC/DC converters is dissipated in the shunt regulator.

DC/DC converter Section

• The digital and analog electronic circuitry operate from two DC/DC converters:– 5 VDC @ 2 Amps Max– +/- 12 VDC @ .33 Amps Max

• Due to the switching characteristic (noise) of DC/DC converters this section is enclosed in the emission-shielding metal box.

• Box penetration feed-thru capacitors are used for all DC voltage and return wires.

• Temperatures are monitored and also penetrate the box using feed-thru capacitors.

Filter Section

• A final section inductor/capacitor filter is used to provide clean noise free power.

• The hydrophone is being operated with a wide amplitude dynamic range of 24 bit ADC capability.

• The power supply filtering is for the analog sections:– hydrophone preamplifier, and – hydrophone analog to digital converter.

Communication

• The instrument data is provided over 12.288 MHz, Manchester encoded/decoded data stream.

• This is 96,000 – 64-bit frames/second.• Within each frame are:

– Two 24 bit digitized analog channels of the hydrophone.

– Two single bit RS232 embedded serial communications 9600 baud. One primary and a secondary backup.

– Six bits for frame synchronization.– Eight unused (zeroed) bits.

Digiquartz

• The Digiquartz is a digital pressure gauge.• 32 bit counters

– Raw count (for high resolution with long periods)– Period count (for quick updates at lower resolution)

• Depth is calculated from the 32kHz variable pressure sensor where frequency is directly proportional to depth.

• Resolution is directly proportional to the integration time.• Temperature compensation is calculated from the

170kHz variable temperature sensor where frequency is directly proportional to temperature.

• The Digiquartz is the same used in NOAA DART buoys to detect tsunami

Hydrophone & ADC

• The analog signal from the hydrophone is digitized with a two channel 24 bit ADC.

• Channel 1 (seismic) is a wide frequency range from 100 seconds to 40 kHz.

• Channel 2 (audio) is a narrow frequency range from 10 Hz to 40 kHz.

• With digital sampling is 96,000 samples per second the analog is low pass filtered at 40 kHz to minimize aliasing.

Serial Data Stream

• The serial data stream provides both engineering and Digiquartz data.

• Engineering data:– 5 DC/DC power supply voltages– 2 cable and sea water return voltages – 1 current of H4 cable– 4 temperatures

• Diqiguartz data:– 2 depth & temperature period counts– 2 depth & temperature free run counts– Calculations of depth with temperature compenstaion

Sample Serial Stream