Power supply control system for heater used in gas sensor

A heater control apparatus used for a gas concentration sensor including a gas chamber, a first cell working to pump thereinto oxygen molecules contained in gasses admitted into the gas chamber and discharge the pumped oxygen molecules, a second cell working to determine a concentration of a specified oxygen containing gas component contained in the gasses having passed through the first cell, a solid electrolyte member on which at least one of the first and second cells is disposed, and a heater heating the first and the second cells, comprising:

• a sensor element resistance value determining circuit working to applying one of a varying voltage and a varying current to the solid electrolyte member and measuring resulting changes in voltage appearing across the solid electrolyte member and current flowing through the solid electrolyte member to determine a resistance value of a sensor element including the solid electrolyte member;
• a heater control circuit controlling a power supply to the heater as a function of a difference between the resistance value determined by said sensor element resistance value determining circuit and a target resistance value;
• a heater resistance determining circuit determining a resistance value of the heater;
• and
• a correcting circuit working to determine a reference resistance value of the sensor element as a function of the resistance value determined by said heater resistance determining circuit based on a predetermined fundamental relation between a resistance value of the heater and a resistance value of the sensor element, said correcting circuit correcting the target resistance value as a function of the reference resistance value.

A heater control apparatus used for a gas concentration sensor including a gas chamber, a first cell working to pump thereinto oxygen molecules contained in gasses admitted into the gas chamber and discharge the pumped oxygen molecules, a second cell working to determine a concentration of a specified oxygen containing gas component contained in the gasses having passed through the first cell, a solid electrolyte member on which at least one of the first and second cells is disposed, and a heater heating the first and the second cells, comprising:

• a sensor element resistance value determining circuit working to applying one of a varying voltage and a varying current to the solid electrolyte member and measuring resulting changes in voltage appearing across the solid electrolyte member and current flowing through the solid electrolyte member to determine a resistance value of a sensor element including the solid electrolyte member;
• a heater control circuit controlling a power supply to the heater as a function of a difference between the resistance value determined by said sensor element resistance value determining circuit and a target resistance value;
• a sensor element temperature determining circuit determining a temperature of the sensor element;
• and
• a correcting circuit working to determine a reference resistance value of the sensor element as a function of the temperature determined by said sensor element temperature determining circuit based on a predetermined fundamental relation between a temperature of the sensor element and a resistance value of the sensor element, said correcting circuit correcting the target resistance value as a function of the reference resistance value.