Investigation and Optimization of the Performance of an Air-Coil Sensor with a Differential Structure Suited to Helicopter TEM Exploration

Sensors

Chen Chen¹  Fei Liu¹  Jun Lin¹  Yanzhang Wang¹ 

[1] College of Instrumentation & Electrical Engineering, Jilin University, Changchun 130061, China; E-Mails:

关键词: helicopter TEM exploration;    ACS;    common-mode noise suppression;    specification optimization;   

DOI  :  10.3390/s150923325

来源: mdpi

【 摘 要 】

An air-coil sensor (ACS) is a type of induction magnetometer used as a transducer to measure the variations of a magnetic field. This device is widely applied in helicopter transient electromagnetic method (TEM) exploration. Most helicopter TEM explorations generate common-mode noise and require extreme ACS specifications, both of which inevitably challenge geophysical explorations. This study proposes a differential air-core coil combined with a differential pre-amplifier to reduce the common-mode noise induced in exploration surveys. To satisfy the stringent performance requirements, including the geometric parameters and electrical specifications, the physical calculations in theory and the equivalent schematic of an ACS with noise location are investigated, respectively. The theory calculation and experimental result for the optimized ACS are then compared on the basis of a differential structure. Correspondingly, an ACS is constructed with a mass, resultant effective area, 3 dB bandwidth, signal-to-noise ratio, and normalized equivalent input noise of 2.5 kg, 5.5 m² (diameter is 0.5 m), 71 kHz, 20 (the varying magnetic field strength is 1 nT/s), and 5.43 nV/m², respectively. These data are superior to those of the traditional induction sensor 3D-3. Finally, a field experiment is performed with a fabricated sensor to show a valid measurement of the time-varying magnetic field of a helicopter TEM system based on the designed ACS.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.