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消像散线圈是透射电子显微镜中的核心部件之一,其电磁场的稳定性影响着电子束的质量。为了获得高稳定的电磁场,必须有高稳定度的恒流源。为了得到高稳定度并且控制比较灵活的恒流源,本设计采用了PLC控制模式,PLC发出信号通过D/A模块输入给稳流板从而把电流给负载。为了使其稳定采用闭环的负反馈系统,并且通过A/D转换器可以检测到电流数值。通过测试验证获得稳定度为1.610-5的恒流源。
An astigmatic coil is one of the core components in transmission electron microscopy. The stability of the electromagnetic field affects the quality of the electron beam. In order to obtain high stability of the electromagnetic field, there must be a high degree of stability of the constant current source. In order to obtain high stability and control of more flexible constant current source, the design uses a PLC control mode, the PLC sends a signal through the D / A module input to the current regulator to the current load. In order to make it a stable closed-loop negative feedback system, and through the A / D converter can detect the current value. Through the test and verify the stability of 1.610-5 constant current source.