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在流量、压力和温度控制中,系统会受到一定的干扰,同时具有低频信号反馈的特点,采用 A/D 转换难以达到抗干扰的要求。为此采用一种新的脉宽调制( PWM) 电路实现转换,将被测模拟信号经过放大、整流以及滤波处理后,与三角波调制信号进行比较,得到 PWM 信号,该信号的占空比与被测量信号的大小成正比。微处理器只要采用定时器测量占空比,就可以计算出输入的模拟信号,其 A/D 转换精度为处理器时钟周期和三角波周期的比值,三角波周期越低,精度越高。这种模数转换电路简单,抗干扰能力强,特别适合低频信号反馈的模数转换。实验结果表明,可以较低成本达到较高转换位数的精度效果。
In the flow, pressure and temperature control, the system will be subject to some interference, but also has the characteristics of low-frequency signal feedback, the use of A / D conversion is difficult to achieve anti-interference requirements. To this end, a new pulse width modulation (PWM) circuit to achieve conversion, the measured analog signal is amplified, rectified and filtered, compared with the triangular wave modulation signal to obtain the PWM signal, the duty cycle of the signal is The size of the measurement signal is proportional. Microprocessor as long as the use of timers to measure the duty cycle, you can calculate the input analog signal, the A / D conversion accuracy of the processor clock cycle and the ratio of the triangular wave cycle, the lower the triangular wave cycle, the higher the accuracy. This analog-digital conversion circuit is simple, anti-interference ability, especially for low-frequency signal feedback analog-digital conversion. The experimental results show that the precision of higher conversion digits can be achieved at a lower cost.