Experiences and results of an experiment lasting more than four years with a mercury in-situ sensor for measuring of the depth in the sea with a precision of 0.3 db which is free from drift and qualified to applicate in-situ as well as a secondary standar

A pressure sensor is described by which the pressure is measured through the electric resistance of a mercury leader in a small quartz-capillary tube. With this sensor can be realized a precision of 0.1 db independent of the pressure in the range of 0-600 bar and more. It was possible to prove that this sensor is free from drift for more than 4 years. Some years ago the first named author undertook researches with the aim to prove that it would be possible to realize a marine depth sensor which could have a sufficient quality in respect of its precision and which would have no drift. One of the solutions for this problem led to a sensor type based on the dependence of the pressure as a function of the electric resistance of a mercury filament. These researches were successful and the results could, be presented on the OCEANS´87. With this presentation the author could show that the realization of such a sensor type for an application in marine research is possible with the specifications required at that time, because a precision of about 0.5 db in the range of 0 to 500 bar was achieved