Magnetoelectric seismometer has many outstanding features, such as low cost, small size, light weight, high sensitivity, low noise, good high frequency response, and reliable operation, simple set up, so these type of seismometer is widely used in several areas. However, because the structure of magnetoelectric seismometer (inertial mass and elastic support module), there has the material and mechanical structure limitation, so the inherent frequency is around between 5 to 30Hz, hard to be lower, hence, the low frequency characteristic is poor. To extend the seismometer's range of application, post compensation is needed. The researchers from both home and aboard proposed many different method to deal with the low frequency response of this seismometer, such as “inverse filter” method, “Lippmann” method, which uses negative resistance and feedback coil. These methods have got some results separately. In this paper, we will propose a low frequency integral method to extend the seismometer's frequency response. It is accomplished through balanced integration and high precision chips to suppress the circuit drifting and noise interference. The results from vibration table shows, after integration, the seismometer's low frequency corner frequency is extended from 2 Hz to under 0.1 Hz, the sensitivity is enhanced from 200V/m·s-1 to 400V/m·s-1.

The seismic signal’s amplitude span is very large, the dynamic range of the observed signal even more than 160dB, so the broadband seismometer output dynamic range should be above 150dB. However, the 24 bits acquisition units usually used, which based on ΣΔ Analog to Digital chip, the dynamic range is just around 130dB. As a result, the acquisition unit can’t resolve the useful signal from tiny earthquake, and when the big earthquake happened, the acquisition unit shows amplitude limiting phenomena. In this paper, we will introduce a method which using two 24 bits ADCs in acquisition unit to extend the dynamic range. That means using one ADC with higher resolution to acquire small signal, and using one ADC with lower resolution to acquire large signal, get the full record of the data. In the end, we combine two acquired data as one 32 bits conversion data. After testing, the dynamic range of experimental prototype used this method reached 155dB＠50SPS.