机车和矿车车轮直径D是在1:20的锥度上标注。一般是先测出尺寸D_1,再测出高度h,得D=D_1-2h(见图1)。这种测量法测量误差大。现绍介一种“弦高法”车轮直径测量仪,能一次测量,且测量精度较高。测量原理如图2所示。测量时各尺寸的关系为: 当L、B、d均为常数时,X值的变化即反应出D的变化,其变化的相互关系可对(1)式全微分 Locomotive and mining wheel diameter D is marked on a 1:20 taper. Generally first measure the size D_1, and then measured the height h, D = D_1-2h (see Figure 1). This measurement method measurement error. Now introduce a “chord method” wheel diameter measuring instrument that can measure once, and the measurement accuracy is high. Measuring principle shown in Figure 2. Measurement of the relationship between the size as follows: When L, B, d are constant, the value of X changes that reflects the change of D, the change of the relationship can be (1) type differential