Exhaust gas toxicity monitor - with electrochemical diffusion cell using measuring and reference electrode, amplifier and signal lamp

摘要

An electrochemical cell to detect the presence of toxic constituents in the exhaust gases of internal combustion engines uses as the measuring electrode, which is exposed to one side to the exhaust gases, a diffusion electrode with a hydrophobic backing plate. A loaded reference electrode and an auxiliary charging electrode are arranged in the same electrolyte. The oxidation flow between measuring and reference electrode is used as a measure for the toxic concentration. The potential of the reference electrode is kept constant by forming in conjunction with the auxiliary electrode and a voltage source. This is a simple device which indicates to any car driver that his catalytic filter has reached the end of its useful life. The device needs no maintenance and is easy to instal. The electrode consists of porous platinum black (20 mg Pt/cm2) with a PTFE bond (40%); the coating consists of a hydrophobic PTFE layer. The reference electrode is a PbO2 layer with Pb contacts and the auxiliary electrode consists of Pb. A switch can be turned from the measuring position to the charging position.