| 主权项 |
1. A control circuit for a gas concentration sensor comprising:
a sweep circuit for supplying a sweep current to a gas concentration sensor, a current value of the sweep current being variable with time; a current detection resistor for detecting a sensor current flowing in the gas concentration sensor; a calculation circuit for calculating an impedance of the gas concentration sensor based on the sensor current flowing in the gas concentration sensor and an inter-terminal voltage of the gas concentration sensor; protective elements for suppressing external noise from being applied to the sweep circuit and the calculation circuit; a first grounding wire connected to a first wire, which connects the sweep circuit and a first terminal of the gas concentration sensor; and a second grounding wire connected to a second wire, which connects a second terminal of the gas concentration sensor and the current detection resistor, wherein the protective elements includes a first protective element and a second protective element, the first protective element being provided in the first grounding wire and causing the sweep current supplied from the sweep circuit to be divided to flow to the first protective element and the gas concentration sensor, and the second protective element being provided in the second grounding wire and causing the sensor current flowing in the gas concentration sensor to be divided to flow to the second protective element and the current detection resistor, and wherein the calculation circuit calculates a first loss current flowing to the first protective element or a second loss current flowing to the second protective element, and calculates the sensor current flowing in the gas concentration sensor by using a calculated loss current. |
