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本文对JEM—1200EX电镜的偏转、消像散系统的数模变换、功放、取样、反馈、测量及故障检查方法进行了分析及讨论。偏转、消像散的范围已存储在计算机的只读存储器中(ROM),该数据按地址总线规定的地址将数据经数据总线通过接口ITF进入偏转、消像散的数模转换单元(O/A)。数模转换单元采用了8到12位码的扩展的方法,而D/A转换采用双极性输出,从而保证了偏转,消像散调节范围和精度。图3中的反馈电阻R_138,有两个作用,一稳定功率放大级的工作,二是反馈给计算机,经模数转换(A/D)使CRT显示偏转、消像散线圈的工作时的电压数值。4.测试偏转单元1的TP10、TP11两点,测量电压值,如电压值不对,请检查、电源单元的晶体管、电阻。
In this paper, the deflection of JEM-1200EX electron microscope, the digital-analogue transformation of the astigmatism system, the power amplifier, sampling, feedback, measurement and fault detection methods are analyzed and discussed. The range of deflections and astigmatisms has been stored in a computer’s read-only memory (ROM), which deflects the data through the interface ITF via the data bus at the address specified by the address bus. The A / A). Digital-to-analog conversion unit uses 8 to 12-bit code expansion method, and D / A conversion using bipolar output, thus ensuring the deflection, astigmatism adjustment range and accuracy. Feedback resistor R_138 in Figure 3 has two functions, a stable power amplifier stage work, the second is fed back to the computer, the analog-digital conversion (A / D) to make the CRT display deflection, dissipating coil voltage when the work Value. 4. Test deflection unit 1 TP10, TP11 two points, measure the voltage value, such as the voltage value is wrong, please check the power unit of the transistor, resistance.