DETECTING DEVICE OF OXYGEN CONCENTRATION

• Main Authors: NAKAJIMA TOYOHEI, MIENO TOSHIYUKI
• Format: Patent
• Language: English
• Published: 19.06.1989
• Subjects: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIRCHEMICAL OR PHYSICAL PROPERTIES; MEASURING; PHYSICS; TESTING

PURPOSE:To keep a heater element at a target temperature, by constituting a bridge circuit of a correction resistor having a resistance value corresponding to a resistance value of the heater element at the target temperature and of the heater element, and by controlling the quantity of electricity fed to a heater by a potential balance retaining means. CONSTITUTION:When a resistance value RH of a heater element 20 lowers below a prescribed value with the lowering of the temperature of an oxygen concentration detecting element, a partial pressure V0 rises in relation to a partial pressure V1 and an output level of a comparator circuit 28 turns to be H. A transistor (Tr) 29 turns ON, a voltage VB is impressed on a series circuit of the element 20 and a reference resistor 27, a heater current flows through the element 20, and the temperature of the oxygen concentration detecting element rises. When the temperature of the element 20 rises with the rise in the temperature of the oxygen concentration detecting element and the resistance value RH thereof exceeds a prescribed value, on the other side, V0 lowers in relation to V1, the output level of the circuit 28 turns L, the feeding of electricity to the element 20 is broken by the Tr 29 turning OFF, and the temperatures of the element 20 and the oxygen concentration detecting element become low. By the repetition of this operation, a heater current is controlled so that the resistance value of the element 20 be a prescribed value.