Gas detection apparatus, gas-sensor control circuit used for gas detection apparatus, and inspection method for gas detection apparatus

A gas-sensor control circuit for controlling a gas sensor element which comprises at least one sensor cell including a solid electrolyte member and a pair of electrodes provided on opposite sides of the solid electrolyte member, and a plurality of external connection terminals electrically connected to the electrodes of the sensor cell, the gas-sensor control circuit comprising:

• a plurality of control terminals electrically connected to respective external connection terminals of the gas sensor element;
• an inspection current supply circuit for supplying an inspection current to an inspected terminal, which is a control terminal to be inspected for presence or absence of a short circuit to a predetermined potential;
• an inspection potential measurement circuit for measuring the potential of the inspected terminal;
• and
• an uninspected terminal impedance increasing circuit for increasing the impedance of the gas-sensor control circuit as viewed from an uninspected terminal, which is a control terminal other than the inspected terminal.

A method for inspecting a gas detection apparatus which includes a gas sensor element which comprises at least one sensor cell including a solid electrolyte member and a pair of electrodes provided on opposite sides of the solid electrolyte member, and a plurality of external connection terminals electrically connected to the electrodes of the sensor cell;

• and a gas-sensor control circuit for controlling the gas sensor element, the gas-sensor control circuit comprising a plurality of control terminals electrically connected to respective external connection terminals of the gas sensor element, an inspection current supply circuit for supplying an inspection current to an inspected terminal, which is a control terminal to be inspected for presence or absence of a short circuit to a predetermined potential, an inspection potential measurement circuit for measuring the potential of the inspected terminal, and an uninspected terminal impedance increasing circuit for increasing the impedance of the gas-sensor control circuit as viewed from an uninspected terminal, which is a control terminal other than the inspected terminal, the method comprising:
• increasing the impedance of the gas-sensor control circuit as viewed from the uninspected terminal by means of the uninspected terminal impedance increasing circuit;
• supplying an inspection current to the inspected terminal by means of the inspection current supply circuit;
• and
• determining, on the basis of the potential of the inspected terminal, whether or not the inspected terminal is short-circuited to the predetermined potential.

A method for inspecting a gas detection apparatus which includes a gas sensor element which comprises at least one sensor cell including a solid electrolyte member and a pair of electrodes provided on opposite sides of the solid electrolyte member, and a plurality of external connection terminals electrically connected to the electrodes of the sensor cell;

• and a gas-sensor control circuit for controlling the gas sensor element, the gas-sensor control circuit comprising a plurality of control terminals electrically connected to respective external connection terminals of the gas sensor element;
• a first inspection current supply circuit for supplying to an inspected terminal a first inspection current flowing in a first direction, the inspected terminal being a control terminal to be inspected for presence or absence of a short circuit to first and second predetermined potentials;
• a second inspection current supply circuit for supplying to the inspected terminal a second inspection current flowing in a second direction opposite the first direction;
• an inspection potential measurement circuit for measuring the potential of the inspected terminal;
• and an uninspected terminal impedance increasing circuit for increasing the impedance of the gas-sensor control circuit as viewed from an uninspected terminal, which is a control terminal other than the inspected terminal, the method comprising:
• increasing the impedance of the gas-sensor control circuit as viewed from the uninspected terminal by means of the uninspected terminal impedance increasing circuit;
• supplying the first inspection current to the inspected terminal by means of the first inspection current supply circuit;
• determining in a first diagnosis step, on the basis of the potential of the inspected terminal to which the first inspection current has been supplied, whether or not the inspected terminal is short-circuited to the first predetermined potential;
• supplying the second inspection current to the inspected terminal by means of the second inspection current supply circuit;
• and
• determining in a second diagnosis step, on the basis of the potential of the inspected terminal to which the second inspection current has been supplied, whether or not the inspected terminal is short-circuited to the second predetermined potential.