A probe-like, vibration-resistant fast-heating electrical heater assembly for use in a pollution sensor of an exhaust monitoring system for internal combustion engines, which comprises an elongate metal tube having concentrically disposed therein a metal conductor rod which is insulated from the tube. At one pair of corresponding ends, the tube and rod carry a ceramic coil form having an open winding on it comprising a helical resistance coil that is disposed in a helical groove of the coil form. Ceramic cement is utilized to secure the coil form in place, and also to mount the conductor rod in the conductor tube whereby a rigid, vibration-resistant assemblage is had that can also withstand high temperatures. The conductor tube is carried in a terminal post that has an annular flange at one end for the purpose of mounting the heater assembly in the associated equipment.
Apparatus for sensing oxygen concentration using a solid electrolyte of cylindrical shape, with a heater disposed within the solid electrolyte, is disclosed. The member supporting the heater, and the leads for the heater, are integrally bonded to the heater through an inorganic bonding member such as glass. By integrally bonding the support member and leads through an inorganic bonding member, the heater length can be reduced.
A heater-incorporating oxygen sensor includes a solid electrolyte oxygen sensor element comprising a solid electrolyte provided with electrodes on both its sides and a heater, said heater being a ceramic heater formed by sintering and embedding a metallized pattern in a ceramic insulator as one solid body, said ceramic heater being disposed within a space surrounded with said oxygen sensor element.
A sensor having a working electrode, a solid electrolyte and a counter electrode forming an electrolytic cell within a protective casing is provided. The sensor is utilized for monitoring the concentration of a specific constituent within a sample fluid by measuring the electrical potential difference between the electrode exposed to the sample fluid, which is the working electrode, and the counter electrode, which is exposed to a reference fluid. A protective casing shields the electrolytic cell from the sample fluid and access to the working electrode is provided by sample fluid ports provided in the protective casing. To minimize the surface area of the working electrode exposed to the sample fluid, a restricter is placed in the channel defined by the protective casing and the working electrode. Additionally, a burn-off gas inlet port is provided to controllably supply burn-off gas to the working electrode surface to burn-off any residual film formed on the working electrode surface exposed to the sample fluid. Additionally, a control system is provided which can use the output from a potential measuring device to control the supply of burn-off gas to the working electrode surface.
