A Study of the stability exhibited by hydrophones when exposed to variations in temperature and hydrostatic pressure

• Main Authors: Ford, Benjamin, Robinson, Stephen, Ablitt, Justin
• Format: Conference Proceeding
• Language: English
• ISSN: 1939-800X
• DOI: 10.1121/2.0001491

Inter-laboratory testing is often undertaken between different National Metrology Institutes (NMIs) by comparison exercises with laboratories calibrating the same hydrophones. The expectation is that results will be within a small tolerance with each other, ensuring consistency among the different laboratories. Hydrophone performance can vary when devices are exposed to different temperatures and hydrostatic pressures, and the degree of variance is different for each model. This can cause sensitivity discrepancies in the data being measured from different NMIs if the environmental conditions are not controlled. NPL has a history of calibrating a variety of hydrophones, additionally NPL operates facilities where temperature and pressure can be controlled, resulting in an ability to calibrate hydrophones in different environmental conditions. In this paper the methodology for characterizing a hydrophone's response at different temperatures and pressure is explained. Additionally a study has been undertaken looking at the stability of commercially available hydrophones in order to determine which hydrophones are stable when transferred between different environments. It was found that some hydrophones exhibit better stability against variations of temperature and pressure than others. Devices constructed with a simple sensor element that consists of a sphere of ceramic exhibit higher stability on average than more complex designs.