Sensor impedance measuring apparatus for improving measurement accuracy of gas sensor
First Claim
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1. A sensor impedance measuring apparatus comprising:
- a circuit line extending through a gas sensor equipped with a sensor element which includes a solid electrolyte body and a pair of electrodes affixed to opposed surfaces of the solid electrolyte body, the sensor element working to produce an electromotive force as a function of concentration of oxygen contained in a gas;
an ac applying circuit disposed in a current path that is a portion of said circuit line and leads to one of the electrodes of the sensor element, said ac applying circuit working to applying one of an alternating voltage and an alternating current swept in level to a positive and a negative side to the sensor element;
a storage device installed in said ac applying circuit, said storage device working to block a flow of direct current and store charges therein;
a voltage sampling circuit working to sample a voltage developed between the sensor element and said ac applying circuit; and
an impedance determining circuit working to determine an impedance of the sensor element as a function of a value of the voltage sampled by said voltage sampling circuit while the one of the alternating voltage and the alternating current is being applied by said ac applying circuit to the sensor element.
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Abstract
A sensor impedance measuring apparatus is provided which is designed to apply one of an alternating voltage swept in level to a positive and a negative side to a sensor element of a gas sensor such as an O2 sensor or an A/F sensor and sample the voltage developed at an end of the sensor element to determine the impedance of the sensor element. The determined impedance is, for example, used to control energization of a heater built in or affixed to the sensor element to control the activation of the sensor element for ensuring the accuracy in measuring the concentration of a gas.
47 Citations
25 Claims
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1. A sensor impedance measuring apparatus comprising:
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a circuit line extending through a gas sensor equipped with a sensor element which includes a solid electrolyte body and a pair of electrodes affixed to opposed surfaces of the solid electrolyte body, the sensor element working to produce an electromotive force as a function of concentration of oxygen contained in a gas;
an ac applying circuit disposed in a current path that is a portion of said circuit line and leads to one of the electrodes of the sensor element, said ac applying circuit working to applying one of an alternating voltage and an alternating current swept in level to a positive and a negative side to the sensor element;
a storage device installed in said ac applying circuit, said storage device working to block a flow of direct current and store charges therein;
a voltage sampling circuit working to sample a voltage developed between the sensor element and said ac applying circuit; and
an impedance determining circuit working to determine an impedance of the sensor element as a function of a value of the voltage sampled by said voltage sampling circuit while the one of the alternating voltage and the alternating current is being applied by said ac applying circuit to the sensor element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A sensor impedance measuring apparatus comprising:
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a circuit line extending through a gas sensor equipped with a sensor element which includes a solid electrolyte body and a pair of electrodes affixed to opposed surfaces of the solid electrolyte body, the sensor element working to produce an electromotive force as a function of concentration of oxygen contained in a gas;
an ac applying circuit disposed in a current path that is a portion of said circuit line and leads to one of the electrodes of the sensor element, said ac applying circuit working to applying one of an alternating voltage and an alternating current to the sensor element;
a voltage sampling circuit working to sample a voltage developed between the sensor element and said ac applying circuit; and
an impedance determining circuit working to determine an impedance of the sensor element as a function of a value of the voltage sampled by said voltage sampling circuit while the one of the alternating voltage and the alternating current is being applied by said ac applying circuit to the sensor element. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A gas concentration measuring apparatus comprising:
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a circuit line extending through a gas sensor equipped with a sensor element which includes a solid electrolyte body and a pair of electrodes affixed to opposed surfaces of the solid electrolyte body;
an ac applying circuit disposed in a current path that is a portion of said circuit line and leads to one of the electrodes of the sensor element, said ac applying circuit working to applying one of an alternating voltage and an alternating current to the sensor element;
a voltage sampling circuit working to sample a voltage developed between the sensor element and said ac applying circuit;
an impedance determining circuit working to determine an impedance of the sensor element as a function of a value of the voltage sampled by said voltage sampling circuit while the one of the alternating voltage and the alternating current is being applied by said ac applying circuit to the sensor element;
a voltage applying circuit disposed in said circuit line, said voltage applying circuit working to apply a voltage to the sensor element;
a current measuring circuit disposed in said circuit line, said current sampling circuit working to measure a current flowing therethruogh which arises from application of the voltage to the sensor element by said voltage applying circuit; and
a controller working to determine a concentration of oxygen in a gas using the current, as measured by said current measuring circuit, said controller working to block the application of the voltage to the sensor element when said ac applying circuit is required to apply the one of the alternating voltage and the alternating current to the sensor element, said controller also working to control the gas sensor using the impedance, as determined by said impedance determining circuit. - View Dependent Claims (20, 21, 22, 23, 24, 25)
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Specification