基于磁通负反馈结构的高灵敏度感应式磁场传感器研制

感应式磁场传感器广泛应用于地球物理电磁勘探仪器,但也是阻碍我国地球物理电磁勘探仪器装备研发和推广应用的瓶颈技术.在我国SinoProbe计划中"地面电磁探测(SEP)系统"项目支持下,我们研制出用于大地电磁测深(the Magnetotellurics MT)方法的高灵敏度磁场传感器.研制过程中,采用磁通负反馈技术,增强传感器系统工作稳定性;采用斩波稳零放大电路技术,有效降低低频1/f噪声对传感器灵敏度的影响;采用高磁导率合金材料,增加磁场传感器的灵敏度.最终,MT磁场传感器工作频率范围为1 m√HZ ~1 k√HZ ,噪声水平0.1 √HZ 时为1.5 pT/√HZ ;1 √HZ 时为0.15 pT/√HZ ;10 √HZ 时为0.03 pT/√HZ ;长度96 cm,重量≤6 kg.理论和测试结果表明:与同类产品比较,本文研制的感应式磁场传感器在≥10 √HZ 时,平均噪声水平从150 fT/√HZ ,下降至30 fT/√HZ ,噪声水平更优,测量精度更高,能够更好地满足MT方法的需求.

Development of search coil magnetometer based on magnetic flux negative feedback structure

The search coil magnetometer (SCM) is a kind of magnetic sensors which is applied widely in oil and mineral explorations, earthquake monitoring, space research and so on. Also SCM is one of indispensable roles in EM exploration device. Funded by China's SinoProbe Plan, the SCM with high sensitivity for the Magnetotellurics (MT) is developed. In this article, the SCM with magnetic flux negative feedback structure is described. The chopper stabilized circuit is applied for removal of the 1/f noise in low frequency. The mu-metal core with high permeability increases the sensitivity of the SCM. The theoretical and test results show that the bandwidth of the SCM is from 1 m√HZ to 1 k√HZ , the noise level at 0.1 √HZ is 1.5 pT/√HZ , at 1 √HZ is 0.15 pT/√HZ , and at 10 √HZ is 0.03 pT/√HZ , respectively. The length of the SCM is 96 cm, diameter is 60 mm, and the weight is less than 6 kg. The SCM presented here can meet the demand of the magnetotellurics (MT) method.