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在本刊今年的第二期中,笔者曾以《导线分布电容对电阻应变测试的影响》为题,从交流电桥的基本原理出发,结合交流供桥、载波放大式应变仪的实际电路,阐明了导线分布电容对电阻应变测试影响的主要因素为应变仪载频的高低和加在相邻桥臂上容差的大小。推证了卧式、半桥、且满足ωRC_0<<1的特定条件下,借助于低通滤波器的帮助,相敏检波器确对容抗不平衡分量具有抑制作用。从而说明其影响的表现形式,主要为仪器的灵敏度降低,严重时将导致放大器阻塞而产生饱和失真。同时,文中还提出了判定测试中所能允许的电容最大不平衡度的方法。在此基础上,本文将综述用以消除导线分布电容影响的四种方法的基本原理,并在理论上加以证明以及上述各方法的适用范围和优缺点。
In the second issue of the journal this year, the author used the title “Effects of Conductive Distributed Capacitance on Resistance Strain Measurement” as the subject. Starting from the basic principles of AC bridges, combined with the actual circuit of AC bridge and carrier amplification strain gages, the author clarified The main factor affecting the resistance strain test is the level of the carrier frequency of the strain gauge and the tolerance of the adjacent bridge arm. It is proved that the phase-sensitive detector can suppress the unbalanced component of capacitive reactance under the special conditions of horizontal and half-bridges and satisfy ωRC_0<<1, with the help of a low-pass filter. This shows the manifestations of its effects, mainly due to the reduced sensitivity of the instrument, which, in severe cases, will cause the amplifier to block and produce saturation distortion. At the same time, the paper also proposes a method for determining the maximum unbalance of the capacitance that can be allowed in the test. On this basis, this article will review the basic principles of the four methods used to eliminate the influence of the distributed capacitance of the wire, and prove in theory and the scope of application and advantages and disadvantages of the above methods.