SN-338数字地震仪和SDZ-751数字地震仪在录取月检记录时都要求得到一张脉冲记录,主要用它来检查前放的相位差和幅度差。但是这张脉冲记录不仅反映了前放的相位差,而且也反映了静电照像记录仪中检流计的相位差。因此要求录制这张脉冲记录的前提条件是检流计的相位没有差别。由于数字地震仪都是在野外条件下进行工作的, Both the SN-338 digital seismograph and the SDZ-751 digital seismometer require a pulse recording when taking monthly records, primarily to check the phase difference and amplitude difference of the preamplifier. However, this pulse recording not only reflects the phase difference of the preamp, but also reflects the phase difference of the galvanometer in the electrophotographic recorder. Therefore, the prerequisite for recording this pulse record is that there is no difference in the phase of the galvanometer. Because digital seismographs are working under field conditions,