Sea-Bird Electronics SBE 38 Bedienungsanleitung PDF herunterladen (Seite 74)

Manual revision 006 Section 4: Deploying and Operating SBE 19plus V2 SBE 19plus V2

Optimizing Data Quality for Profiling Applications

Our deployment recommendations are only general guidelines, and are

focused primarily on maximizing data quality. Actual sea state conditions, and

winch and deck gear configurations, may require some adaptation in order to

achieve best data quality and avoid mechanical problems.

The SBE 19plus V2 is optimized for profiling rates of 0.5 to 2 meters/second,

with 1 meter/second generally providing the best compromise between data

quality and profile resolution. The 19plus V2 pump maintains a constant and

optimum flow rate, which ensures that the sensor response times are not

dependent on the profiling rate. Adjust the profiling rate of the 19plus V2

based on the amount of ship motion (i.e., sea state) imparted to the cable, and

the size, weight, and drag of the underwater package at the end of the cable.

Generally, use a faster rate in rougher seas, allowing the 19plus V2 to stay

clear of turbulent wakes that are shed downward when the ship heaves up;

shed wakes are an error source from which all CTDs suffer. When the sea is

very calm, the 19plus V2 can be lowered more slowly (for example,

10 to 20 cm/second) to give greater vertical resolution.

Like for other CTDs, the common configurations of the 19plus V2 are

intended for obtaining downcast data, because the sensors are oriented so that

the T-C Duct inlet passes through relatively undisturbed water as the CTD is

lowered. As the CTD is raised (upcast), the sensors sample the turbulent wake

of the package, resulting in lower quality data. If planning to sample on the

upcast, consider the following:

• Vertical orientation – In the typical, sensors-down configuration, the

sensors are in the wake of the housing on the upcast, providing poor data

quality. If you must have good quality upcast data, invert the 19plus V2 so

that the T-C Duct is at the top (ignore the downcast data for this

configuration).

• Horizontal orientation (for example, under SBE 32 Carousel Water

Sampler) - Position other instruments, sample bottles, etc. so that they are

not directly above the T & C sensors and do not thermally contaminate the

water that flows to the sensors at the T-C Duct inlet.

When a 19plus V2 is installed on a water sampler, good conductivity and

optional dissolved oxygen data can be collected, even when stopped to collect

a water sample, because water continues to flow through the sensors at a fixed

and optimal rate.

Whether sampling on the upcast and/or downcast, position the T-C Duct

inlet so that other instruments, sample bottles, etc. do not thermally

contaminate the water that flows past the sensors.

Where the water temperature is very different from the temperature at which

the 19plus V2 has been stored, better results are obtained if the 19plus V2 is

allowed to equilibrate to the water temperature at the surface (soak) for several

(3 – 5) minutes before beginning the profile. The reason is not that the

electronics are temperature sensitive - they are not - but that the thermal

influence of the instrument housing on the water entering the cell will be

reduced. If the difference between water and storage temperature is extreme,

allow more soak time.

Note:

See Pump Operation – Profiling

Mode for information on the minimum

soak time required to ensure proper

pump operation.

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