在某些只有低频脉冲信号的场合,能否使用普通数字量输入模块来替代昂贵的专用计数器模块进行频率测量,通过分析数字量输入模块和PLC系统的工作原理,对普通DI模块测量脉冲信号的各种制约条件进行了理论研究,并计算出可测量脉冲信号的最大范围。在此基础上,以液体流量计为例,介绍了用普通DI模块实现流量累计计量的步骤和方法。实际效果表明,DI模块能较好地实现测量低频脉冲信号的目的。 In some cases only the low-frequency pulse signal, whether the use of ordinary digital input module instead of expensive special counter module for frequency measurement, through the analysis of digital input module and PLC system works, ordinary DI module to measure the pulse signal Various constraints were studied theoretically and the maximum range of measurable pulse signals was calculated. On this basis, taking the liquid flow meter as an example, the procedure and method of realizing the total flow measurement with the ordinary DI module are introduced. The actual results show that, DI module can better achieve the purpose of measuring low-frequency pulse signal.