Method and sensing device for measuring predetermined gas component in measurement gas

A method of measuring a predetermined measurement gas component in a measurement gas, comprising the steps of:

• introducing said measurement gas containing said measurememt gas component having bonded oxygen to be measured, from an external measurement gas space into a first processing zone under a predetermined diffusion resistance;
• pumping out oxygen in said first processing zone by the aid of an oxygen-pumping action effected by a first electrochemical pumping cell so that a partial pressure of oxygen in an atmosphere in said first processing zone is lowered to a degree sufficient to control a partial pressure of oxygen in a subsequent second processing zone;
• introducing said atmosphere into said second processing zone under a predetermined diffusion resistance, said second processing zone being in serial communication with said first processing zone;
• pumping out oxygen in an atmosphere in said second processing zone by the aid of a second electrochemical pumping cell so that said partial pressure of oxygen in said atmosphere is controlled to have a low value of partial pressure of oxygen which does not substantially affect measurement of an amount of said measurement gas component;
• introducing said atmosphere into a third processing zone under a predetermined diffusion resistance, said third processing zone being in serial communication with said second processing zone;
• reducing or decomposing said measurement gas component introduced from said second processing zone, in an atmosphere in said third processing zone;
• and
• outputting, with the use of an electrochemical sensor cell, an electromotive force corresponding to a partial pressure of oxygen in said atmosphere in said third processing zone, defined by oxygen produced in said reducing or decomposing step to obtain a detected output value from which said amount of said measurement gas component in said measurement gas is determined.

A sensing device for measuring an amount of a predetermined measurement gas component in a measurement gas by measuring an amount of oxygen produced by reducing or decomposing said measurement gas component having bonded oxygen in said measurement gas, said sensing device comprising:

• a first processing zone comparted from the outside, said first processing zone communicating with an external measurement gas space;
• a first diffusion rate-determining means for introducing said measurement gas containing said measurement gas component, from said measurement gas space into said first processing zone under a predetermined diffusion resistance;
• a first electrochemical pumping cell comprising a first oxygen ion-conductive solid electrolyte and a pair of electrodes provided in contact therewith, for pumping out oxygen from said first processing zone by applying a current between said pair of electrodes so that a partial pressure of oxygen in an atmosphere in said first processing zone is lowered to a degree sufficient to control a partial pressure of oxygen in a subsequent second processing zone;
• said second processing zone comparted from the outside, said second processing zone communicating serially with said first processing zone;
• a second diffusion rate-determining means for introducing said atmosphere in said first processing zone having said lowered partial pressure of oxygen into said second processing zone under a predetermined diffusion resistance;
• a second electrochemical pumping cell comprising a second oxygen ion-conductive solid electrolyte and a pair of electrodes provided in contact therewith, for pumping out oxygen from said second processing zone by applying a current between said pair of electrodes so that a partial pressure of oxygen in an atmosphere in said second processing zone is controlled to have a low value of partial pressure of oxygen which does not substantially affect measurement of said amount of said measurement gas component;
• a third processing zone comparted from the outside, said third processing zone communicating serially with said second processing zone, for reducing or decomposing said measurement gas component in an atmosphere introduced from said second processing zone;
• a third diffusion rate-determining means for introducing said atmosphere in said second processing zone having said controlled partial pressure of oxygen into said third processing zone under a predetermined diffusion resistance;
• a third electrochemical pumping cell comprising a third oxygen ion-conductive solid electrolyte and a pair of electrodes provided in contact therewith, for pumping out oxygen produced by reducing or decomposing said measurement gas component in said third processing zone, by applying a current between said pair of electrodes;
• and
• a current-detecting means for detecting said pumping current allowed to flow by the aid of an pumping action effected by said third electrochemical pumping cell.

A sensing device for measuring an amount of a predetermined measurement gas component in a measurement gas by measuring an amount of oxygen produced by reducing or decomposing said measurement gas component having bonded oxygen in said measurement gas, said sensing device comprising:

• a first processing zone comparted from the outside, said first processing zone communicating with an external measurement gas space;
• a first diffusion rate-determining means for introducing said measurement gas containing said measurement gas component, from said measurement gas space into said first processing zone under a predetermined diffusion resistance;
• a first electrochemical pumping cell comprising a first oxygen ion-conductive solid electrolyte and a pair of electrodes provided in contact therewith, for pumping out oxygen from said first processing zone by applying a current between said pair of electrodes so that a partial pressure of oxygen in an atmosphere in said first processing zone is lowered to a degree sufficient to control a partial pressure of oxygen in a subsequent second processing zone;
• said second processing zone comparted from the outside, said second processing zone communicating serially with said first processing zone;
• a second diffusion rate-determining means for introducing said atmosphere in said first processing zone having said lowered partial pressure of oxygen into said second processing zone under a predetermined diffusion resistance;
• a second electrochemical pumping cell comprising a second oxygen ion-conductive solid electrolyte and a pair of electrodes provided in contact therewith, for pumping out oxygen from said second processing zone by applying a current between said pair of electrodes so that a partial pressure of oxygen in an atmosphere in said second processing zone is controlled to have a low value of partial pressure of oxygen which does not substantially affect measurement of said amount of said measurement gas component;
• a third processing zone comparted from the outside, said third processing zone communicating serially with said second processing zone, for reducing or decomposing said measurement gas component in an atmosphere introduced from said second processing zone;
• a third diffusion rate-determining means for introducing said atmosphere in said second processing zone having said controlled partial pressure of oxygen into said third processing zone under a predetermined diffusion resistance;
• an electrochemical sensor cell comprising a fourth oxygen ion-conductive solid electrolyte and a pair of electrodes provided in contact therewith, for outputting an electromotive force corresponding to a partial pressure of oxygen in said atmosphere in said third processing zone, defined by oxygen produced by reducing or decomposing said measurement gas component;
• and
• a voltage-detecting means for detecting said electromotive force outputted from said electrochemical sensor cell.