DESCRIPTION
The SEAGAUGE Wave & Tide Recorder combines Sea-Bird's reliable semiconductor-memory electronics, stable time base, precision thermometer, and quartz-crystal pressure sensor to provide wave and tide recording of unprecedented resolution and accuracy, along with high-quality temperature information. A second input connector for a conductivity sensor is also standard.
The SBE 26 (shown above) is being secured in its optional mounting fixture. After installation at a mooring site, the fixture allows removal and precise repositioning by a diver. Tools are not required, and there are no loose parts to misplace.
The SBE 26 continuously integrates pressure samples to obtain water level measurements unaffected by wave action, and also independently burst-samples pressure at rates up to 4 Hz for wave amplitude calculation. Water level integration and wave burst sampling intervals and durations are programmable. The large memory permits frequent water level recording and highly detailed wave characterization. For example, with an 8M byte memory and optional lithium batteries, a 120-day deployment could include water level measurements every 15 minutes and 20-minute, 2 Hz wave-burst samples eight times a day.
The SBE 26 includes SEASOFT© for Waves, a comprehensive package of Windows and DOS programs including deployment planning, instrument setup and data retrieval, plotting, auto-spectrum and time series analysis, and statistics reporting.
The example shown at
right
is an auto-spectrum plot of surface wind waves obtained from one burst sample of 1024
pressure measurements. The error bars correspond to 90% confidence intervals.
Using SEASOFT for Waves and an IBM PC-compatible computer, the recorded data (wave, tide, temperature, and optional conductivity) is uploaded after recovery via an RS-232 interface, without opening the housing. The battery compartment is separated from the electronics by a moisture-proof seal, and contains 9 standard alkaline D-cells. Longer deployments are possible using lithium batteries.
SENSORS
The standard pressure sensor is a 45 psia Quartzonix temperature-compensated transducer (other ranges, using a Digiquartz sensor, are optional). Temperature is measured with an aged thermistor imbedded in the SEAGAUGE end cap. An SBE 4 conductivity sensor (optional) may be interfaced via the second bulkhead connector and clamped to the SEAGAUGE housing.
PROGRAMMING AND RECORDING
The tide integration time is user-programmable in minute increments over a range of 1 to 30,000 minutes. Temperature data is recorded with each tide integration. Waves are characterized by burst sampling with the number of samples per burst, burst interval, and burst integration time programmed by the user. A tide and temperature measurement consists of 4 bytes (8 bytes with optional conductivity); each sample in a wave burst uses 3 bytes.
SPECIFICATIONS
| Temperature (°C) |
Conductivity (S/m) optional |
Pressure | |
| Measurement Range | -5 to +35 | 0 to 7 | 13 ranges, from 0 to 1 m (15
psia) to 0 to 6800 m (10,000 psia) |
| Accuracy | 0.02 | 0.001 | 0.01% of full scale (3 mm for 45 psia range) |
| Resolution | 0.01 | 0.00002 |
Tide: |
| Wave: 0.4 mm (0.016 in.) for 0.25-second integration; 0.1 mm (0.004 in.) for 1-second integration |
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| Calibration | +1 to +32¹ | 1.5 - 6¹ | 0 psia to F.S. Pressure |
| Repeatability | 0.005% of full scale (1.5 mm for 45 psia range) |
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| Hysteresis | 0.005% of full scale (1.5 mm for 45 psia range) |
¹Measurements outside the specified calibration ranges will be at reduced accuracy due to extrapolation errors.
Counter time-base: ± 2 ppm stability vs. temperature (-5 to 35 °C); ± 2 ppm per year aging
Memory: 8 Mbyte static RAM; back-up battery gives 2 years data retention after main battery is exhausted
Real-time clock: 15 seconds per month stability; battery-backed
Weight, in air: 6.4 kg (14 lbs) with alkaline batteries; mounting fixture weighs 3.6 kg (8 lbs)
Housing: Acetal Copolymer Plastic to 680 meters; titanium to 6800 meters
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