如果在单片机控制的仪表里用PWM方式完成D/A输出，将会使成本降低到12位D/A芯片的十分之一左右。我们在S系列流量仪表中采用了这种方式，使用效果非常理想。下面介绍一下PWM方式D/A的构成原理。(If in the microcontroller control instrument, using PWM way to complete the D/A output, will reduce the cost to 12 bit D/A chip about 1/10. We have adopted this method in the S series flow meter, and the result is very satisfactory. The following describes the PWM mode D/A composition principle.)