Distortion,as an important parameter of the geophone,its test method directly determines the accuracy of the test result.In the test process of existing tester for geophone,noise generated by the circuit is relatively large;the test accuracy cannot meet the test requirement for high precision geophone.Differential input method is used to complete the test of distortion parameters;the differential signal is produced by using the sinusoidal signal generator inside the high performance D/A conversion chip.The second order active low pass filter is used in signal processing part;the cut-off frequency is limited at 100 Hz to realize low pass effect.By way of fully differential design,the common mode interference in circuit was reduced,to make the sinusoidal signal going through the geophone much closed to the standard sinusoidal signal.In signal collection part,24 bit A/D conversion chip is used to reach the requirement of high precision collection accuracy.The experimental test shows that the distortion measurement system can meet the error standard of geophone tester,and the precision can reach 10-5.The test circuit designed by the full differential method improves the test accuracy;in addition,selecting high performance chip also plays an important role in the test results of the system.%失真度作为地震检波器的一项重要参数,其测试方法直接决定测试结果的精确度.现有检波器测试仪在失真度测试过程中受电路本身产生的噪声干扰较大,测试精度不能满足高精度地震检波器的测试要求.采用差分输入法进行失真度参数的测试,差分信号由高性能数模转换芯片内部的正弦信号发生器产生.信号处理部分采用二阶有源低通滤波器,使截止频率限定在100 Hz,实现低通效果.通过全差分的设计方式,减小了电路中的共模干扰,使通过地震检波器的正弦信号极大限度地接近标准正弦信号.信号采集部分选用24位模数转换芯片,达到高采集精度测试的要求.试验结果表明,失真度测试系统满足地震检波器测试仪器误差标准,精确度达到10-5数量级.全差分方法设计的测试电路在一定程度上提高了测试精度;同时,高性能芯片的选取对系统的测试结果也具有重要作用.
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