Noise characteristics of transient electromagnetic sensor
Shuan‐Hong Zhang · Progress in geophysics · 2014
In order to improve the sensitivity of transient electromagnetic(TEM) system and increase the detecting depth,the noise characteristics of transient electromagnetic sensor are studied in this paper.We propose a background noise model of transient electromagnetic sensor,and calculated results indicate that noise power spectrum density presents a band-limited white noise characteristic,and the maximum spectrum density is observed at resonant frequency which is equivalent to the thermal noise of matched resistance,approximately.In order to remove the influence of environmental noise on measurement.an inverse series pair of small coil is used to replace TEM receiver coil.The comparison between theoretical and measured results verifies the correction of the noise model.The background noise of TEM sensor is estimated according to the noise model,which is shown 9.8nV/m2.The transient stacked and the window stacked methods are discussed,and the sensor noise can be reduced to7.5 pV/m2 by using these methods,which is much lower than the environmental noise.We propose a shielding model of receiver coil,and the model indicates that sensor sensitivity can be effectively improved by using the coil shielding method.