故障现象：开机（在封闭状态下）描笔单向偏移至上不动，零点可调，但只有原正常移动范围的；调增益，灵敏度转换和从封闭到观察切换，描笔都会大幅度偏离中心，再调零点，又可回到中心，但极不稳定。稍再调零点，描笔又会大幅度偏向上或下，做人体心电可描记出无交流干扰的不 Symptom: The boot (in the closed state) is unilaterally shifted to the top, the zero point is adjustable, but only the original range of normal movement; tuning gain, sensitivity conversion and switching from closed to observation, the writing will be a great deviation The center, again zeroing, can return to the center, but it is extremely unstable. After a little more zeroing, the pen will be more or less up or down, so that the human heart can be traced without interference.