Time-domain electromagnetic induction method including on-time and off-time illumination is widely developed in unexploded ordnance (UXO) detection. The secondary field response detected in off-time is almost ineffective for targets with small size and great depth due to fast signal attenuation and low signal-to-noise ratio at late stage. In this paper, the on-time response for UXO detection with TEM system is discussed in detail. Firstly, the on-time response of a sphere is calculated theoretically and compared with the off-time response. Secondly, the transmitting circuit with four NMOS is designed to generate desired transmitting current to measure on-time response effectively. Finally, the on-time and off-time response of several targets are measured simultaneously. Results show that the late signal-to-noise ratio of on-time response is much higher and the attenuation of target with small size and iron pipe is slower than the off-time response, which is consistent with the theoretical results.

包括开启时间和关闭时间照明的时域电磁感应方法在未爆弹药 (UXO) 检测中得到广泛发展。由于后期信号衰减快、信噪比低，关断时检测到的二次场响应对于尺寸小、深度大的目标几乎无效。在本文中，详细讨论了使用 TEM 系统进行 UXO 检测的准时响应。首先，从理论上计算球体的开启时间响应，并与关闭时间响应进行比较。其次，具有四个NMOS的发射电路被设计为产生所需的发射电流以有效地测量导通时间响应。最后，同时测量多个目标的开启时间和关闭时间响应。