Title: Autonomous Instrumentation for Oceanography

Autonomous Sea Level Gauges (SLG)

Parameters measured

• Sea Level elevation

• Sea Water temperature

Operating Principle

• The gauge is a pressure based device
• The pressure sensing element is a single-crystal silicon thin-diaphragm.
• The silicon wafer, which is the piezo-resistive pressure sensing element of the transducer, exhibits change in its resistivity when subjected to stress induced by the pressure of the overlying sea water.
• Pressure is translated to sea level elevation either by dynamic calibration or using water density and acceleration due to earth's gravity.

Measurement Accuracy

• 0.1% of full-scale range

Main Components of the Gauge

The gauge consists essentially of the following two elements:

• Sea unit that houses the transducer
• Shore unit that houses the logger

Data Storage

• Data is stored in the onboard flash memory of the logger
• Data recording interval is programmable (usually set at 15 minutes).
• The memory capacity is 512 kbyte, capable of storing approximately 5 months' data

Data Retrieval

• Data is read from the logger through a menu-driven program that resides in a Windows-based computer

NIO Sea Level Gauge operational at Tokkaradi harbour, Ghana (West Africa)