Volvo Ocean Adventure Instrumentation

Ocean-i Sensor Unit

The Instrument Packages:

At Saturn Solutions, we were responsible for the core processor for the instrument package (Ocean-i sensor) including the tilt and roll sensor, and the design and production of the thermistor chain. The instruments were installed on the yachts prior to the race start whilst they were at the race village in Southampton. During the race, servicing of the equipment took place at the stopovers. This was performed by Saturn Solutions personnel and included exchanging the instrument memory cards. Data collected from the instruments onboard the yachts can be seen here.

The Ocean-i Sensor Unit

The Ocean-i Sensor Unit is based around an enhanced RSIC processor core with 32Kb of dedicated scratchpad RAM, 8Kb in-system programmable Flash RAM and a further 512 bytes of non-volatile EEROM used to store configuration and calibration information. The sensor design includes 8 RS232 sensor ports, 1 RS232 controller port, a battery-backed real-time clock and a 4Mb removable non-volatile Flash RAM module which saved all the data collected during the race. It is this memory module that was removed at the end of each leg of the race to act as a backup to the data that was been sent to the UK scientists who were coordinating the data management. During the race itself, Ocean-i collected and selected data from the various sensors every hour, processed it and sent it on to the yacht's communications module. The sampling procedure is described here.

The Optical Sensors

radiometers on the yacht stern mast

The vessels were equipped with two Ramses-ARC radiance sensors which measured the upwelling radiance from the sea surface, and one Ramses-ACC incoming radiance sensor which measured the ambient light. These were fitted to the yachts as shown.

The sensors have darkened channels from 950 - 1100 nm. The typical spectral range is from 350 - 950 nm over 183 channels of 3.3 nm.

The downwelling irradiance sensor is fitted with a cosine collector.
The two radiance sensors have an angular field of view of 7^o to measure upwelling radiance above the sea surface (water leaving radiance plus specular reflection). Measurements from one of these sensors were selected for storage based on quality control criteria.

Pdf files can be downloaded for more information on the radiance and irradiance sensors.

The Tilt/Roll Sensor

This is a stand alone EZ-Tilt 2045 two axis inclination module with an RS232 interface from Advanced Orientation Systems. The Tilt/Roll sensor was incorporated into the Ocean-i Sensor unit by mounting it on a specially made bracket on top of the Ocean-i pcb. This required the Ocean-i Sensor unit to be mounted in a specific orientation in order for the Tilt/Roll sensor to be level and showing zero when the boat was upright. The Tilt/Roll sensor was interrogated by Ocean-i before each collection from the optical sensors to ascertain the orientation of the yacht. When the yacht was heeled for long periods the Tilt/Roll sensor helped Ocean-i to decide which optical sensor was better orientated to measure sea colour. The tilt and roll data was also transmitted back to the Race Office as part of the routine information collected from the yachts.

The Thermistor Unit

Thermistor Unit

The Thermistor Unit is a standalone sensor based on an enhanced RISC micro-controller with 2Kb of program Flash RAM and 512 bytes of scratchpad RAM. It is connected to 4 high accuracy in-system calibratable 16-bit serial Flash analogue to digital converters which convert the signal from the thermistor chain. The thermistor data was averaged over several measurements, converted to real temperatures and sent, via the RS232 output, to the Ocean-i Sensor.

The Thermistor Chain

The Thermistor Chain was manufactured on 5-core ribbon cable, used for its small profile and flexibility, using R-T (resistance-temperature) curve matched, interchangeable, high precision thermistors with a negative temperature coefficient. The thermistors themselves are protected by thin-wall heatshrink tubing and the whole assembly was bonded into the leading edge of the yacht's rudder or keel, leaving a flying lead running out of the stock. The chain has a working range of -50慢 to + 150慢 of which we used a 34慢 window from -4慢 to +30慢.