Research often means coping with ex-treme conditions to retrieve the right data. Marine research is a case in point. Underwater sensors that plumb the depths of the world’s ocean have to withstand not only temperature differences but also extreme pressures, yet still deliver reliable readings. Up until now, measuring devices secured to cables or hawsers have generally been used to record such data. This technique is proven and reliable, but the disadvantage is that the data does not become available until after the devices have been recovered. A different concept used in conjunction with state-of-the-art microdrive systems now allows completely independent recording by free-ranging underwater sensors and virtually online data transmission.
As part of the international Argo project to monitor the oceans of the world, around 2,500 free-ranging floats have been deployed so far. In the final phase of the research project, the aim is to have 3,000 permanently deployable floats. The main job of all the sensors is to measure water temperature and salt levels at different depths. Other readings such as clouding of the water and plankton content can be added at a later stage as required. German sensor manufacturer Optimare Sensorsysteme AG, Bremerhaven, is responsible for building and servicing the NEMO floats contributed by Germany. To make the floats as universally produc-tive as possible, they were designed as independently operating units. This means they are free-ranging, driven only by the currents of the ocean, and capable of recording data below ice as well as from a range of configurable depths. In order to transmit the data via satellite, they come to the surface at pre-deter-mined intervals. To achieve the necessary level of reliability and absolutely maintenance-free depth control, Optimare works with German compact drive systems manufacturer FAULHABER. This is how they managed to come up with a robust, compact system for precise depth control of the underwater sensors.