Ultra low frequency pressure transducer calibration

Abstract
This work is devoted to description of practical experience in solution of several scientific and technical problems arising in ocean environmental ultra low frequency acoustic field measurements fulfilled by means of pressure piezoelectric transducer. Ultra low frequency (ULF) range presented here lies in natural nonstationary noise field periods interval from 1000 to 10 seconds. In the course of development of measuring utility solution of following practical problems was proposed : - construction special very high capacity up to several mF piezoelectric pressure probe and special mechanical grid protecting the probe from environmental currents ; - constructing and adjusting of first stage special type charge preamplifier adequately working in ULF range with input impedance up to 10¹³ W and maximum input charge 10⁵ pC ; - construction of special mechanical and temperature calibration means providing very slow harmonic change of static pressure with amplitude accuracy from several millimeters of water gauge and temperature accuracy from 0.1°C on the surface of transducer.