Gas sensing element and a method for measuring a specific gas concentration

A gas sensing element comprising:

• a sample gas chamber into which a sample gas is introduced;
• a reference gas chamber into which a reference gas is introduced;
• a sensor cell located in both of said sample gas chamber and said reference gas chamber for detecting the concentration of a specific gas contained in said sample gas;
• an oxygen pump cell located in said sample gas chamber for pumping oxygen gas from or to said sample gas chamber;
• and
• an introducing passage including at least one pinhole provided on a surface of said oxygen pump cell for introducing said sample gas into said sample gas chamber,
• wherein said surface of said oxygen pump cell faces an outside of said gas sensing element,
• a porous diffusion resistive layer is provided on said surface of said oxygen pump cell so as to cover a portion corresponding to said introducing passage, and
• said porous diffusion resistive layer has a thickness in a range from 0.05 to 0.3 mm.

A gas sensing element comprising:

• a sample gas chamber into which a sample gas is introduced;
• a reference gas chamber into which a reference gas is introduced;
• a sensor cell located in both of said sample gas chamber and said reference gas chamber for detecting the concentration of a specific gas contained in said sample gas;
• an oxygen pump cell located in said sample gas chamber for pumping oxygen gas from or to said sample gas chamber;
• and
• an introducing passage including at least one pinhole provided on a surface of said oxygen pump cell for introducing said sample gas into said sample gas chamber,
• wherein said surface of said oxygen pump cell faces an outside of said gas sensing element,
• a porous diffusion resistive layer is provided on said surface of said oxygen pump cell so as to cover a portion corresponding to said introducing passage, and
• said porous diffusion resistive layer has a mean pore diameter in a range from 200 to 2,000 Å.

A gas sensing element comprising:

• a sample gas chamber into which a sample gas is introduced;
• a reference gas chamber into which a reference gas is introduced;
• a sensor cell located in both of said sample gas chamber and said reference gas chamber for detecting the concentration of a specific gas contained in said sample gas;
• an oxygen pump cell located in said sample gas chamber for pumping oxygen gas from or to said sample gas chamber;
• and
• an introducing passage including at least one pinhole provided on a surface of said oxygen pump cell for introducing said sample gas into said sample gas chamber,
• wherein said surface of said oxygen pump cell faces an outside of said gas sensing element,
• a porous diffusion resistive layer is provided on said surface of said oxygen pump cell so as to cover a portion corresponding to said introducing passage, and
• said porous diffusion resistive layer has a porosity in a range from 3 to 20%.

A gas sensing element comprising:

• a sample gas chamber into which a sample gas is introduced;
• a reference gas chamber into which a reference gas is introduced;
• a sensor cell located in both of said sample gas chamber and said reference gas chamber for detecting the concentration of a specific gas contained in said sample gas;
• an oxygen pump cell located in said sample gas chamber for pumping oxygen gas from or to said sample gas chamber;
• and
• an introducing passage including at least one pinhole provided on a surface of said oxygen pump cell for introducing said sample gas into said sample gas chamber,
• wherein said surface of said oxygen pump cell faces an outside of said gas sensing element,
• a porous diffusion resistive layer is provided on said surface of said oxygen pump cell so as to cover a portion corresponding to said introducing passage, and
• a relationship 0.5≦D2/(D1+D2)≦0.9 is established when D1 represents a diffusion resistance of said introducing passage and D2 represents a diffusion resistance of said porous diffusion resistive layer.

A method for measuring a specific gas concentration of a sample gas by using a gas sensing element,

• said gas sensing element comprising:
• a sensor cell including a measuring electrode and a reference electrode provided on a solid electrolytic member, said measuring electrode being located in a sample gas chamber and said reference electrode being located in a reference gas chamber;
• a pump cell including a pair of pump electrodes provided on opposite surfaces of a solid electrolytic member, one of said pump electrodes being located in said sample gas chamber, wherein said sample gas chamber is filled with a porous member that has a porosity in a range from 3-30%;
• a sensor circuit including a first ammeter and a power supplier for measuring a current flowing in said sensor cell;
• and
• a pump circuit including a second ammeter and a variable power supplier for measuring a current flowing in said pump cell, and
• said method comprising:
• measuring an oxygen gas concentration of a sample gas based on a current value measured by said second ammeter;
• controlling said variable power supplier based on a measured oxygen gas concentration value;
• and
• measuring a specific gas concentration of said sample gas based on a current value measured by said first ammeter.