Electrochemical membrane sensor

Claim 1

An electrochemical membrane sensor adapted to be immersed in a test fluid so as to sense desired chemical species within the test fluid, said sensor comprising: an open housing that defines a chamber, a membrane sealing the chamber from said test fluid, said chamber adapted to be filled with an electrolytic medium, said membrane being selectively permeable so as to allow said desired chemical species from the test fluid to permeate into the electrolytic medium, an anode and a cathode spaced apart within the chamber and each adapted to be electrically connected to a measurement transducer that responds to current between the anode and cathode, said current being proportional to the concentration of said desired chemical species within the test fluid, and an acoustic transduction element which is adapted to stir the test fluid adjacent the membrane so that the concentration of said desired chemical species permeating into the electrolytic medium is representative of the concentration of the desired chemical species in the test fluid as a whole, and which is also adapted to clean contaminants from the outer surface of the membrane exposed to the test fluid, said acoustic transduction element including said membrane as a mechanical component thereof, wherein said membrane is a piezoelectric film transducer so that sonic and ultrasonic energy transmitted by the piezoelectric action of said membrane will cause the membrane to be excited to separately produce low frequency vibration modes and high frequency ultrasonic modes according to the energy transmitted and to stir the test fluid adjacent the membrane and clean any contaminants from the outer surface of the membrane and to cause circulation of electrolytic medium within the chamber.