日立钨灯丝电镜的说明书里设置偏压给了个最大值:The maximum bias voltage value is linked with the accelerating voltage and it is obtainable by the following equation. Maximum value = E × (1 + 0.9785 × 10-6 × E)/258.71 按照这个公式100KV时最大偏压才424V。可是机器勾选自动偏压后都有八九百伏特了。我真是搞不明白这个公式干什么用的?请各位高人指点。