Eric-Triangle Pulses?

[Anonymous]

I was reading a paper on the AeroTEM system, and found to my surprise that their using not only a triangle pulse but also a coincident loop geometry. Have you tried this yet? The advantages claimed are:maximization of target-to-backround response,simplier and sharper anomilies,enhancement of discrete conductors (whatever they are), and insensitivity to conductor strike direction. Lets see and they also mentioned the system shows the potential to detect and recognize bodies that exhibit a form of polarizability, rather than simple electrical conductivity.
Would be interesting to try this out on Chris Hakes red hot soil.
By the way, the article appeared in the October 2001 issue of The Leading Edge entitled "AeroTEM characteristics and field results".
Randy Seden

 

[Anonymous]

Hi Randy,
Their coincident coil is simply a concentric coil. They do not mention if they balance it or not although a standard PI does not need balancing as the signal is sampled after the ground effect has died away. What I find most interesting is the claim that electrical currents in the overburden and country rocks disperse outwards rapidly away from the receiving coil. They claim that this greatly reduces the background responses and the target is much better resolved. Here is part of what they say. Maybe Eric can explain this to us? Dave. * * *
Coil Geometry:
AEROTEM is the only operational helicopter EM system that employs a coincident-loop coil geometry (the receiving coil is situated centrally within the transmitting loop). With this configuration electrical currents in the overburden and country rocks disperse outwards rapidly away from the receiving coil, whereas the currents in the confined target maintain good coupling. The result is that background reponses are greatly reduced and the target is much better resolved