Externally Powered / Compressibility Compensated Yoyo

The EP/CC-Yoyo is a moored profiler designed for special applications.

It is originally developed to monitor changes caused by winter convective events in the polar regions (Greenland Sea).

Basic demands were
- deep profiles (typically 4000 m)
- many profiles (typically 360, i.e. 1 profile each day for 1 year)
- self contained vehicel (internal data storage to avoid problems with
  ice in arctic regions)
- measure C,T and p with precision high enough to indicate convective events
  in polar regions
- light construction for easy handling.

These requirements have a number of implications with respect to the construction.
First, the vehicel has to be pressure resistant to withstand 400 bar, leading to a basic weight of the instrument. Floation used to balance the instrument in the water has also to be resistant to this pressure.
Second, the energy supply must suffice for the many and deep casts. It is not practical to use a construction in which all the energy that is needed for the vertical movement is carried within the vehicel itself. This energy, say in form of batteries, would be associated with increasing weight that would have to be balanced in water, thus increasing also the volume of the vehicel. By a big volume, however, the energy needed to achieve a certain speed is increased.