Behaviour of Electrets in Difficult Climatic Conditions and Estimation of their Life

摘要

This paper describes a method of diaphragm accelerate testing for electrets microphones constructed with Teflon components,such as per-fluoro-alkoxy (PFA) and fluoro ethylene propylene (FEP).The microphone diaphragms are considered to he polarized in high electric fields,so hundreds of volts can be achieved as surface potential.Maintaining these values enough time is important for long term functioning of high stability microphones.Such tests are to be performed in laboratories for months,even years,trying to obtain the minimum loss of surface potential in time.A decreasing of the test interval can be obtained using accelerating methods,which simulates real situations through harsh climate conditions (temperature and humidity higher than normal).An empirical formula has been obtained,which allows estimation of normal lifespan of electrets: if an electrets microphone can maintain constant his surface potential for X hours at temperature T,then at T-30° C will be able to maintain it for 10X hours.This formula is useful for considerable reducing time tests.