Dissolved oxygen (DO)

RBR standard instruments with a "DO" in the name, such as RBRconcerto3 C.T.D.DO.PAR (Fig. 12), use third-party dissolved oxygen sensors.

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Fig. 12.    An RBRconcerto³ C.T.D.DO.PAR with an OxyGuard DO sensor

Overview
Galvanic dissolved oxygen sensors (OxyGuard) generate an electrical current proportional to the amount of oxygen dissolved in seawater and are rated for depths of up to 1700m.

Optical dissolved oxygen sensors (Rinko®, Aanderaa®) measure the drop in luminescence of a chemical dye in the sensor cap, caused by interacting with the oxygen dissolved in seawater. Being based on phosphorescence, their scientific concept is similar to the ODO sensor manufactured by RBR.

OxyGuard

During deployments, always orient the sensor downwards to reduce debris collecting at the aperture.
Store the DO sensor in the dedicated storage cap, included with the instrument.

Parameter Value

Range

0 to 600%

Initial accuracy

±2% oxygen saturation

Resolution

1% of saturation

Time constant

~10s, 90% step change at 20°C

Galvanic dissolved oxygen sensors need refurbishment if you observe any of the following:

  • There is salt build-up around the aperture

  • Protective membrane is damaged

  • Electrolyte solution inside the storage cap is cloudy

  • Sensor readings are out of range

Derived parameters: oxygen concentration

Rinko

RBR standard instruments support the Rinko optical dissolved oxygen sensor (Rinko III), shown in Fig. 12.

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Fig. 13.    A Rinko optical dissolved oxygen sensor.

During deployments, always orient the sensor downwards to reduce debris collecting at the aperture and minimise direct sunlight. Store the sensor in the dedicated storage cap, included with the instrument.

Parameter Value

Range

0-200% O2 saturation

Resolution

0.01-0.04%

Accuracy

Non-linearity ±2% full scale

Depth rating

7000m

Derived parameters: oxygen concentration

Aanderaa

RBR standard instruments support the Aanderaa optical dissolved oxygen sensors Optode 4531 (Fig. 14) and Optode 4831F(Fig. 15).

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Fig. 14.    The Aanderaa optode 4531
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Fig. 15.    The Aanderaa optode 4831F
Parameter O2 concentration O2 saturation

Measurement range

0-1000μmol/L

0-300%

Resolution

<0.1μmol/L

0.05%

Accuracy
Optode 4531
Optode 4831F

 
<8μmol/L
<2μmol/L

 
<5%
<1.5%

Depth rating
Optode 4531
Optode 4831F

 
100m
300m / 3000m/ 6000m

Derived parameters: oxygen saturation or oxygen concentration