| 摘要 |
PROBLEM TO BE SOLVED: To provide an analog output circuit that reliably detects abnormality in a digital/analog converter and the like and is inexpensive, and to provide a mass flow rate control device that uses it. SOLUTION: The circuit is an analog output circuit that outputs an analog signal based on a digital output signal from a digital arithmetic circuit, via a digital/analog converter and a gain circuit. The digital arithmetic circuit incorporates a pulse wide modulator and an analog/digital converter. A DAC output signal from the digital/analog converter and a PWM signal having been made at a constant voltage via a low-pass filter based on an output of the pulse wide modulator are input into an addition-subtraction circuit. The addition-subtraction circuit outputs the addition-subtraction result of the DAC output signal and the PWM signal to the analog/digital converter. The digital arithmetic circuit outputs an abnormality signal, on the basis of the addition-subtraction result. COPYRIGHT: (C)2009,JPO&INPIT |
