Technology Groups > Marine Sensor Systems > Performance

A Low cost portable echo sounder integrated with a GPS and a telemetry systems was designed, developed and tested up to 80m water depth off-chennai with indigenously made transducer.

200 kHz Integrated portable echo sounder

GPS interface and RF telemetry were provided in the echo sounder to enable the user to note the position of the vessel and water depth at any location in the boat and is given in FiG.9. The remote hand held display for the echo sounder makes it convenient for the fishing trawlers and small boats to see the depth and location of the boat during their voyage.

Pressure testing of semiconductor devises

Very few electronic components are directly exposed to the hydrostatic pressure exerted by the water column above them. Most of the components and PCBs are housed in either in pressure casing, which can withstand the pressure or in a pressure compensated chamber. In the former case the chamber is tested for the pressure rating in a hyperbaric chamber. However all the components which are to be placed inside the pressure compensated casing can be qualified by testing in a pressure chamber with suitable connectors and bulkheads. Hence Marine Sensors and Electronic group had taken-up the task of developing the semiconductor devices that are used in the underwater power supplies. As a first step, the group started testing commercially available diodes, transformers and other devices at high pressure to under stand their behaviour at higher hydrostatic pressures.

High pressure testing chamber facility

With the available pressure chamber at NIOT the V-I characteristics of a commercially available diode were studied at 50 bar pressure for one month. A change in temperature and pressure inside the pressure case was noticed during the study and this was correlated with the power and the properties of the oil used. These studies provided a valuable input for designing the underwater pressure cases and pressure compensators.

V-I characteristics of a diode in air & oil under 50 bar pressure

In addition to diodes, locally available transformers were procured and were tested under high pressures up to 50 bar for a prolonged period of 1 month.  The variation of insulation and resistance of the transformer, placed in a hydraulic oil bath with BDV {20kV at distance of 2.5 mm}, was studied and the typical results obtained are shown in figure 12. Only less than 10% variation in the insulation resistance values of the transformer was noticed under 50 bar constant pressure for 1month.

Insulation resistance  variation with pressure