Polargraphic oxygen sensor for gas operated water heater - contains element acting as probe and second element acting as limiting probe for safety circuit

摘要

A polargraphic oxygen detector is located downstream of a heat exchanger located in the combustion gas flow. The detector provides an output for an electronic regulator to control speed of an exhaust fan in the top of the heater. The detector comprises two detecting elements with ceramic plates at the base which conduct oxygen ions. Measuring electrodes are deposited on the front of the plates and conductors extend to a contact. These electrodes are covered with a diffusion barrier. On the rear of the plates is fixed via an isolating layer a thin metallic heating conductor from which conductor channels extend to the contact. One detector element acts as a probe while the other acts as a limit flow probe. This provides a signal to cut off the fuel inlet when the oxygen level exceeds a limit valve.