초록 ▼

Using a sole Nox sensor Nox concentration and oxygen concentration are measured accurately. A measurement device for measuring NOx concentration and oxygen concentration comprises an NOx sensor 2 having a first measurement chamber 20 communicating via a diffusion rate regulating layer 4d with the ga

Using a sole Nox sensor Nox concentration and oxygen concentration are measured accurately. A measurement device for measuring NOx concentration and oxygen concentration comprises an NOx sensor 2 having a first measurement chamber 20 communicating via a diffusion rate regulating layer 4d with the gas under measurement and a second measurement chamber 26 communicating with the first measurement chamber 20 via diffusion rate regulating layers 6d, 22d. A first pump cell 4 and an oxygen concentration measurement Vs cell 6 are formed on the first measurement chamber 20, while a second pump cell 8 is formed on the second measurement chamber 26. Inside of the first measurement chamber 20 is controlled to a constant low oxygen concentration by controlling the first pump current IP1 so that output of Vs cell 6 will equal a reference voltage VC0. By applying a constant voltage across the second pump cell 8 NOx in the second measurement chamber 26 is decomposed to pump out oxygen. Thus NOx concentration and oxygen concentration are measured from the second pump current IP2 and from the first pump current IP1, respectively. During measurement, sensor temperature is detected from the internal resistance of the Vs cell for controlling heater current supplied to heaters 12, 14 to maintain a constant sensor temperature.

대표청구항 ▼

[ What is claimed is:] [1.]1. A method for measuring an oxygen concentration and a nitrogen oxide concentration in a gas under measurement comprising:(a) providing a NOx sensor comprising a first measurement chamber, a second measurement chamber, a first oxygen pumping cell, a second oxygen pumping

[ What is claimed is:] [1.]1. A method for measuring an oxygen concentration and a nitrogen oxide concentration in a gas under measurement comprising:(a) providing a NOx sensor comprising a first measurement chamber, a second measurement chamber, a first oxygen pumping cell, a second oxygen pumping cell and a heater,said first measurement chamber comprising said first oxygen pumping cell and an oxygen concentration measuring cell and communicating with the gas under measurement via a first diffusion rate regulating portion, said first oxygen pumping cell comprising an oxygen ion conductive solid electrolyte layer sandwiched between a pair of porous electrodes, said second oxygen pumping cell comprising another oxygen ion conductive solid electrolyte layer sandwiched between another pair of porous electrodes, said second measurement chamber communicating with the first measurement chamber via a second diffusion rate regulating portion, and said heater being adapted for heating the cells, said solid electrolyte layers being disposed in lamination;wherein an oxygen concentration measurement cell for measuring the oxygen concentration of the gas under measurement supplied to the second measurement chamber is disposed between said first and second oxygen pumping cells in a laminating direction of said solid electrolyte layers;(b) causing a current flow in said first oxygen pumping cell so that a deviation from a target value of an output voltage of the oxygen concentration measurement cell will be zero, thereby controlling an oxygen concentration in the first measurement chamber to a constant value;(c) applying a constant voltage across said second oxygen pumping cell in a direction of pumping oxygen out of the first measurement chamber;(d) measuring a value of a current flowing in the second oxygen pumping cell which is indicative of the nitrogen oxide concentration in the gas under measurement;(e) simultaneously measuring a value of the current flowing in the first oxygen pumping cell which is indicative of the oxygen concentration in the gas under measurement and(f) measuring a temperature of the oxygen concentration measuring cell and correcting the current flowing in the second pumping cell based on said measured temperature.