| 摘要 |
PURPOSE:To prevent a sensor from entering a runaway state while maintaining a wide measurable range of gas concentration by stopping a rise in monitor voltage above a specific output current value and holding the voltage constant. CONSTITUTION:A reference power source E1 generates the sensor monitor voltage Vm to be applied to the sensor S and a reference power source E2 determines the maximum value of the sensor monitor voltage Vm. Further, operational amplifiers OP1 and OP2 convert the output current of the sensor S into a voltage signal. Then an amplifier OP2 feeds the voltage signals converted by the amplifiers OP1 and OP2 back through a circuit M to amplify the monitor voltage Vm. When the output of the amplifier OP3 is smaller than the voltage E2 of the reference power source, the output of an amplifier OP4 outputs a voltage as high as the output of the amplifier OP3 and when the output of the amplifier OP3 is larger than the voltage E2 of the reference voltage, the output of the amplifier OP4 is the voltage E2. Then the output of the amplifier OP2 is sent to an output amplifiers L and measured as the output current of the sensor S. |
