PURPOSE: To make it possible to hold constant field strength between both electrode lines, by causing its control portion to control the output voltage of its electric source in response to a voltage raising or lowering command signal from its command portion so that the output voltage is raised or lowered such as to cause the potential difference detected between both probes to equal a reference potential difference.
CONSTITUTION: A command portion 13 compares with a reference potential difference an actual potential difference detected between probes 6a, 6b both of which are arranged between electrode lines 1a, 1b and, in accordance with the result of the comparison, the command portion 13 yields and sends a voltage raising or lowering command signal to a control portion 14, which thereby controls the output voltage of an electric source 5 so that it is raised or lowered, thus causing the actual potential difference detected to equal the reference potential difference. In this way, the field strength between both electrode lines 1a, 1b can be held constant regardless of bad conductor films that may be stuck on the surface of each of electrodes 3 forming the respective electrode lines 1a, 1b, and/or fluctuations in the conductance of sea water.
ARAI HIROSHIGE
MAEHATA HIDEHIKO
TSUKAHARA MASANORI
