讨论了机车定置试验系统中的转速测量问题。首先介绍了机车试验系统的基本功能和结构及其对转速测量的具体要求;根据这些要求,对测功机和机车柴油机转速的测量方案进行了设计,并研究了通过PLC的DI输入对中低转速进行测量的方法,使整个设计既满足系统的特殊要求,又具有较高的性价比。 The problem of speed measurement in locomotive locating test system is discussed. First of all, the basic function and structure of locomotive test system and its specific requirements for speed measurement are introduced. According to these requirements, the measurement schemes of dynamometer and locomotive diesel engine speed are designed. And through the DI input of PLC, Speed ​​measurement method, so that the entire design not only to meet the special requirements of the system, but also has a high cost.