Aloha Proof Module Design Cabled Observatory Presentation School of Ocean and Earth Science and Technology February 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 Digiquartz DQ (under).

Hydrophone ADC Manchester

Top View Manchester 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 2 Amps Max –+/- 12 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 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