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SENSOR PRINCIPLE

SENSOR PRINCIPLE

1.Equations

1-1: Seawater density, σt and potential temperature equations
1-2: Dissolved Oxygen Concentration Equation
1-3: Equation of the Practical Scale of Salinity

 
 

2.Measurement principle

2.1: Electromagnetic flowmeter
Principle: Faraday's law of electromagnetic induction: if a conductor moves across a magnetic field, it will generate a current voltage in the conductor → electromotive force. Considering water (as a conductor) moving across a magnetic field, the electromotive force is proportional to the velocity of the fluid. The proportionality follows a linear relationship.

2.2: Temperature sensor
Principle: Thermistor ( Therm ally Sensitive Trans istor → material which electric resistance varies with temperature .

2.3: Conductivity sensor
Principle: measurement of the electric resistance, which in turn varies with seawater salinity.

2.4:Chlorophyll-a and Turbidity
Chlorophyll-a sensor principle: the sensor measures the intensity of chlorophyll-a fluorescence, which is a sub-product from the photosynthesis process.
Turbidity sensor principle: backscatter light detection. The emittance signal peak is at 880 nm (near-infrared) and the receiver detects the backscattered light from suspended particles in the water.

2.5: Dissolved Oxygen sensor (DO sensor)
Principle: the DO sensor is coated with photostimulable phosphor (PSP) on the outside of the pressure-resistant acrylic optical window, measuring the phase difference between phosphorescent time lengths.

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