Sensors in use // University of Oldenburg

Sensors in use: CTD

The use of the CTD rosette on the FS Heincke

CTD is the abbreviation for:

The CTD rosette consists of the CTD probe, which contains the three The CTD rosette consists of the CTD probe, which contains the three different sensors, and the rosette / water sampler, a metal frame to which the 12 water samplers are attached.

The CTD probe is used to

Measure water properties (temperature, conductivity, water pressure)
obtain information about specific water areas (density, salinity, water depth)

The probe can be used in deep waters such as lakes or oceans.

The CTD and rosette are lowered from a ship into the water using a cable and then collect data separately. These measured values are transmitted to a computer on the ship and stored. The data collected at
can then be used to create "profiles" of the water depths.

Preparing the CTD for use

Folding the CTD rosette

The CTD rosette is slowly lowered on a winch; it is "lowered". It is attached to a cable that allows data from the probe to be viewed in real time on the ship.

The CTD rosette of the FS Heincke can be deployed at depths of up to 600 metres. As the FS Heincke is mainly travelling in the North Sea, the depth is sufficient. A dive here takes about 10 minutes.

However, some CTD rosettes are also used in deeper waters and can sink to depths of up to 8,000 metres. In such cases, the dive can last several hours.

Most sensors, e.g. for pressure or salt content, are available multiple times. The measurements are constantly compared in order to avoid errors.
During a measurement, the CTD rosette is only lowered to a few metres above the seabed to prevent the devices from touching the bottom.

Measurement data

The sensors record measurement data during descent and ascent.
During the descent, the CTD rosette penetrates the different water layers for the first time.
The previously still water layers are now swirled up.
For this reason, the data taken during the ascent can be falsified. As a rule, they are not used.

Other values can be calculated from various measured values. For example, the measured water temperature and the conductivity of the water can be used to determine the salt content.