Abstract: An analog input signal obtained from an analog sensor group 104A and first and second calibration voltages obtained by high-precision voltage-dividing resistors are successively selected by a multiplexer, digitally converted through an AD converter and then input to a microprocessor. The microprocessor calculates a collinear approximate coefficient based on the first and second calibration voltages in cooperation with a program memory, and corrects the digital conversion value to the analog input signal by using the approximate coefficient, thereby correcting a linear error of the conversion characteristic of the AD converter. In the calculation of the approximate coefficient, upper and lower limit check is executed on measurement values and calculation coefficients, and also plural calculation results are averaged to enhance the precision.

Abstract: Respective positive terminal electric potentials of exhaust gas sensors are sequentially selectively inputted to an analog input terminal of a multi-channel AD converter through a multiplexer. An offset voltage is applied to respective negative terminals of the exhaust gas sensors. This offset voltage is inputted to another input terminal of the multi-channel AD converter. A microprocessor detects a generating voltage of the exhaust gas sensors by the difference between a digital converting value of the positive terminal electric potential and a digital converting value of the negative terminal electric potential. The microprocessor also individually judges that each of the digital converting values is excessively small and excessively large. Thus, the microprocessor judges the existence of ground, sky short circuit and disconnection abnormalities of the negative terminal and the positive terminal.

Abstract: Respective positive terminal electric potentials of exhaust gas sensors are sequentially selectively inputted to an analog input terminal of a multi-channel AD converter through a multiplexer. An offset voltage is applied to respective negative terminals of the exhaust gas sensors. This offset voltage is inputted to another input terminal of the multi-channel AD converter. A microprocessor detects a generating voltage of the exhaust gas sensors by the difference between a digital converting value of the positive terminal electric potential and a digital converting value of the negative terminal electric potential. The microprocessor also individually judges that each of the digital converting values is excessively small and excessively large. Thus, the microprocessor judges the existence of ground, sky short circuit and disconnection abnormalities of the negative terminal and the positive terminal.

Abstract: A single state detector circuit can quickly detect short-circuit and open-circuit abnormalities of a load controlled by a power transistor. A DC power supply, the load and the power transistor are serially connected with one another, so that a switching terminal voltage of the power transistor is binarized into high and low levels by the state detector. The power transistor is linearly controlled by a constant-current control circuit so as to suppress an excessive current, and power supplied to the power transistor is interrupted by an overheat interruption circuit. Upon occurrence of a short-circuit in the load during generation of an energization command, a switching terminal voltage of the power transistor becomes stabilized at a high level without intermittent operation, which is detected by the state detector. Upon occurrence of an open-circuit during generation of a deenergization command, a low switching terminal voltage is detected by the state detector.

Abstract: A single state detector circuit can quickly detect short-circuit and open-circuit abnormalities of a load controlled by a power transistor. A DC power supply, the load and the power transistor are serially connected with one another, so that a switching terminal voltage of the power transistor is binarized into high and low levels by the state detector. The power transistor is linearly controlled by a constant-current control circuit so as to suppress an excessive current, and power supplied to the power transistor is interrupted by an overheat interruption circuit. Upon occurrence of a short-circuit in the load during generation of an energization command, a switching terminal voltage of the power transistor becomes stabilized at a high level without intermittent operation, which is detected by the state detector. Upon occurrence of an open-circuit during generation of a deenergization command, a low switching terminal voltage is detected by the state detector.