Apparatus for monitoring impurities in a gas stream.

摘要

A device is provided comprising a piezoelectric material and at least one coating reactive with trace quantities of oxygen and/or water in reactive and inert gases. The piezoelectric material is bonded to a conductor for delivering an alternating electric current and to a conductor for transmitting resonant vibration frequency of the crystal. The reactive coating has an effective thickness which provides a serviceable life for the coating while not being so thick as to prevent vibration of the piezoelectric material.