| 摘要 |
PURPOSE:To attain strong resistance to external noise, by separating the connection among a control input and a pulse width output of a sawtooth wave generator and a digital circuit electrically, in an A/D converter using the analog-pulse width conversion. CONSTITUTION:A sawtooth wave generator 10 generates a sawtooth wave by repeating charge/discharge on a capacitor 11 for a prescribed voltage from a constant voltage circuit 1 via an operational amplifier 21. The generated sawtooth wave is inputted to voltage comparators 23, 27 and 31 of each channel and compared with an analog input. Each comparison output and a sawtooth wave controlling input are connected to a microcomputer 44 with photocouplers 45, 46 47 and 17. The microcomputer 44 clears a counter and turns on a sawtooth wave controlling circuit, then the counter is summed until the end of conversion is discriminated with the comparator output and the count value is taken as the conversion output. |
