# US 2008/0185289 A1 · Sensor control device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2008/0185289 A1 - Document ID: US20080185289A1 - Status: Published application - Kind: A1 - Application number: 12/010,682 - Filed: 2008-01-29 - Published: 2008-08-07 - Earliest claimed: 2007-02-05 - Assignees: Denso Corporation - Inventors: Mikiyasu Matsuoka; Tomoo Kawase; Eiichi Kurokawa - Web page: https://patentgrep.com/patent/US20080185289A1 ## CPC - G01N 27/4065: {Circuit arrangements specially adapted therefor} - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract A current detection resistance in a sensor control device is connected to a sensor element. The current flowing in the sensor element is detected through the current detection resistance. The current detection resistance is connected to an inverting amplification circuit for outputting an air/fuel output voltage to be transferred to a microcomputer. An offset setting circuit is connected to one input terminal of an operational amplifier in the inverting amplification circuit. The offset setting circuit is comprised of a switching element, a resistance connected in series to the switching element, and two dividing voltage resistances whose common node is connected to the resistance. The offset setting circuit generates and gives an offset to the A/F output voltage. The switching element is turned ON and OFF based on an offset switching signal transferred from the microcomputer. ## Claims ### Claim 1 A sensor control device for controlling the operation of a sensor element made up of solid polymer electrolyte capable of detecting a concentration of a specific gas component contained in a target gas in a wide detection range, comprising: a current detection resistance for detecting a current flowing in the sensor element and generating an element current signal; an amplification circuit for inputting the element current signal through one of positive and negative input signal terminals thereof, and for amplifying the element current signal; an offset setting circuit for setting an offset, connected to a middle node between an input resistance and a feedback resistance in a feedback line for the amplification circuit; and offset switching means for switching the offset determined by the offset setting circuit according to the element current signal, which is continuously supplied from the sensor element, regarding the concentration of the specific gas component contained in the target gas. ### Claim 2 (depends on 1) The sensor control device according to claim 1, wherein the offset switching means switches the offset, which is generated by the offset setting circuit, by connecting/disconnecting the middle node between the input resistance and the feedback resistance in the feedback line of the amplification circuit to/from the offset setting circuit. ### Claim 3 A sensor control device for controlling the operation of a sensor element made up of solid polymer electrolyte capable of detecting a concentration of a specific gas component in a target gas in a wide detection range, comprising: a current detection resistance for detecting a current flowing in the sensor element and generating an element current signal; an amplification circuit of one of an inverting type and non-inverting type for inputting the element current signal through one input signal terminal thereof, and for amplifying the element current signal; an offset setting circuit for setting an offset, which is connected to one of the one input signal terminal for receiving the element current signal and the other input signal terminal of the amplification circuit; and offset switching means for switching the offset determined by the offset setting circuit according to the element current signal regarding a concentration of the specific gas component contained in the target gas. ### Claim 4 (depends on 3) The sensor control device according to claim 3, wherein the offset switching means switches the offset, which is determined by the offset setting circuit, by connecting/disconnecting the one input signal terminal of the amplification means to/from the offset setting circuit. ### Claim 5 (depends on 3) The sensor control device according to claim 3, wherein the offset setting circuit sets a plurality of offset values, and the offset switching means selectively selects one of the plurality of offset values. ### Claim 6 (depends on 3) The sensor control device according to claim 3, wherein the target gas is an exhaust gas emitted from an internal combustion engine, and the sensor control device detects an air/fuel (A/F) ratio of the exhaust gas in an A/F ratio detection range, and the A/F ratio detection range comprises: a stoichiometry detection range for use in a stoichiometry combustion control, which is as a part of the whole A/F ratio detection range detectable by the sensor element: and a lean detection range for use in a lean combustion control, which is as a part of the whole A/F ratio detection range detectable by the sensor element, wherein the offset switching means judges whether the A/F ratio detection is performed under the stoichiometry detection range or the lean detection range according to the A/F ratio control, and the offset switching means switches the offset according to the judgment result. ### Claim 7 (depends on 6) The sensor control device according to claim 6, wherein the A/F ratio detection rage includes a rich detection range for use in a rich combustion control as a part of the whole A/F ratio detection range, the offset switching means selects one of the stoichiometry detection range, the lean detection range, and the rich detection range in order to detect the A/F ratio using the selected one, and switches the offset based on the judgment result. ### Claim 8 (depends on 6) The sensor control device according to claim 6, wherein each of the stoichiometry detection range, the lean detection range, and the rich detection range includes a stoichiometry value. ### Claim 9 (depends on 8) The sensor control device according to claim 8, further comprising a circuit characteristic detection means configured to detect a circuit characteristic error based on an output signal of the amplification circuit at the time when the current flowing in the sensor element is forcedly halt. ### Claim 10 (depends on 1) The sensor control device according to claim 1, further comprising a plurality of resistances for amplification to determine the amplification factors for the amplification circuit; and amplification factor switching means for switching the resistances for amplification so that one of the resistances for amplification are used as an input resistance and the remaining resistances for amplification are used as a feedback resistance. ### Claim 11 (depends on 10) The sensor control device according to claim 10, wherein the wide detection range for detecting the gas concentration of the specific gas component contained in the target gas is divided into different detection ranges in advance, the amplification factor switching means switches the resistances for amplification so that the amplification factor of the amplification circuit is increased when the gas concentration of the specific gas component contained the target gas is detected in a narrow detection range in the different detection ranges, and switches the resistances for amplification so that the amplification factor of the amplification circuit is decreased when the gas concentration of the specific gas component contained in the target gas is detected in a wide detection range in the different detection ranges. ### Claim 12 (depends on 10) The sensor control device according to claim 10, wherein the target detection gas is an exhaust gas emitted from an internal combustion engine, the sensor control device detects an A/F ratio of the exhaust gas in an A/F ratio detection range, and the A/F ratio detection range comprises: a whole A/F ratio detection range in which the sensor element is detectable; a stoichiometry detection range, which is a part of the whole A/F ratio detection range, for use in a stoichiometry combustion control; and a lean detection range, which is a part of the whole A/F ratio detection range, for use in a lean combustion control in a part of the whole A/F ratio detection range, the sensor control device so controls that: the offset switching means does not give any offset to the amplification circuit when the sensor element detects the A/F ratio of the exhaust gas under the whole A/F ratio detection range, and the amplification factor switching means selects the resistances for amplification so that the amplification factor is decreased; the offset switching means does not give any offset when the sensor element detects the A/F ratio of the exhaust gas under the stoichiometry detection range, and the amplification factor switching means selects the resistances for amplification so that the amplification factor is increased; and the offset switching means gives an offset when the sensor element detects the A/F ratio of the exhaust gas under the lean detection range, and the amplification factor switching means selects the resistances for amplification so that the amplification factor is increased. ### Claim 13 (depends on 11) The sensor control device according to claim 11, wherein the target detection gas is an exhaust gas emitted from an internal combustion engine, the sensor control device detects an A/F ratio of the exhaust gas in an A/F ratio detection range, and the A/F ratio detection range comprises: a whole A/F ratio detection range in which the sensor element is detectable; a stoichiometry detection range, which is a part of the whole A/F ratio detection range, for use in a stoichiometry combustion control; and a lean detection range, which is a part of the whole A/F ratio detection range, for use in a lean combustion control in a part of the whole A/F ratio detection range, the sensor control device so controls that: the offset switching means does not give any offset to the amplification circuit when the sensor element detects the A/F ratio of the exhaust gas under the whole A/F ratio detection range, and the amplification factor switching means selects the resistances for amplification so that the amplification factor is decreased; the offset switching means does not give any offset when the sensor element detects the A/F ratio of the exhaust gas under the stoichiometry detection range, and the amplification factor switching means selects the resistances for amplification so that the amplification factor is increased; and the offset switching means gives an offset when the sensor element detects the A/F ratio of the exhaust gas under the lean detection range, and the amplification factor switching means selects the resistances for amplification so that the amplification factor is increased. ### Claim 14 (depends on 12) The sensor control device according to claim 12, wherein the sensor control device detects the A/F ratio of the exhaust gas in the A/F ratio detection range, and the A/F ratio detection range is further comprised of a rich detection range, which is a part of the whole A/F ratio detection range, for use in a rich combustion control, and the sensor control device so controls that the offset switching means gives an inverted offset, which is obtained by inverting the offset for use in the lean detection range, when the sensor element detects the A/F ratio of the exhaust gas under the rich detection range, and the amplification factor switching means selects the resistances for amplification so that the amplification factor is increased. ### Claim 15 (depends on 1) The sensor control device according to claim 1, wherein the amplification circuit comprises one of a constant current source and a pull-down resistance at an output stage thereof.