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众所周知,为了防止热电偶在使用过程中损坏,造成“跑温”事故,一些与热偶配套的显示仪表,包括动圈温度指示调节仪及电子电位差计,都带有断偶保护装置。一般来说,引入的断偶保护信号在热电偶正常工作,即热电偶回路的电阻R_W很小时,对显示仪表的指示值影响很小。只有在热电偶断路即R_W→∞时,它才使显示仪表的指针指向刻度终端。带有断偶保护信号的显示仪表在进行示值误差检定时,常常会出现一些特殊现象。这一现象可能造成检定误差增大,甚至完全失效。下面我们分别就动圈仪表及电子电位差计来讨论这一问题。 1.XCT型动圈温度指示调节仪国产XCT型仪表断偶保护装置,如图1所示。当
As we all know, in order to prevent the use of thermocouples in the process of damage, resulting in “running temperature ” accident, some and thermocouple supporting display instruments, including moving coil temperature indicator and electronic potentiometer, are equipped with broken even protection device . In general, the introduction of the broken even protection signal in the normal work thermocouple, thermocouple circuit resistance R_W is very small, indicating the value of the instrument has little effect. Only when the thermocouple opens R_W → ∞, it directs the indicator of the display meter to the end of the scale. Display instruments with broken even protection signals often show some special phenomena when checking the indication error. This phenomenon may result in increased verification error, or even complete failure. Here we discuss the issue of moving coil instruments and electronic potentiometer respectively. 1.XCT type moving coil temperature indicator Domestic XCT type instrument broken even protection device, shown in Figure 1. when