Maximum target distance

About a coil diameter, perhaps slightly more - it greatly depends on the coil design (wound or PCB, core-no core etc)

Would this not be a function of the "range" of the magnetic flux induced by the coil? For instance, could it be possible to introduce a permalloy core to the design, thereby concentrating magnetic flux in the core centre to produce a more elongated flux pattern, hence a greater North<->South flux "range"?

Lastly, is it possible to use high power tank ccts in conjunction with the LDR solution with some kind of external driver circuitry?

This is truely a remarkable design! Many thanks and kindest regards.

Hello,

Exactly! that's why I wrote that it greatly depends on the coil design. Magnetic core is a great way of extending the range.

Could you please explain what "high power tank ccts in conjunction with the LDR solution" to keep us on the same page?

Just a conversation piece at this stage. I have an interest in metal detection and possibly metal identification. I work in the Mining Industry where there are various opportunities for this technology.

In essence, I thought that in order to extend sensitivity beyond the current coil-width limit, a higher energy resonance tank circuit might produce more flux and hence greater sensitivity/detection range. I might be mistaken though.

Kindest Regards 

The relative change will be the same - current is a multiplier in all the equations, and does not matter in the end of the day for resolution (only for SNR).

In any case, LDC1000 was designed to be a low-current device, and cannot drive high currents.

Fair enough :-) 

So if I can create a coil with the correct physical and impedance/resonance characteristics, what I should really be interested in is the Signal to Noise Ratio. I noticed in another thread there is interest in detection of metal as material passes along a conveyor belt.

This is an interest for Mining as well, to reduce damage to equipment from metal coming off heavy equipment from time to time. Other areas are sensing metal in oil from gearboxes, sensing gear teeth to alarm when gear teeth are lost.

Other areas could be land/personal mine detection, wall stud detection, nail detection in recycled wood/boards, metal detection in food manufacture, and so forth (There are many applications off the top of my head)

I have ordered a board for experimentation. Will keep you appraised of ideas we chose to follow-up.

Again many thanks.

Kindest Regards

Would it work to drive a dedicated tx coil while blanking the input to the rx coil?

Alternate between tx and rx modes...

I'm sorry, I don't quite understand the mode of operation. Could you please elaborate?

Hi David,

Yes, these applications (with the exception of wooden wall stud) are great candidates for the LDC technology.

Please keep us posted on your results, or shout if you need any help.

I'm suggesting something of a combinational pulse inducton and tank induction approach. 

The TX signal would be a pulse delivered by a separate coil to create eddy currents on the target.

During the pulse the RX coil and LDC1000 would be negated in some way in an attempt to eliminate overload and recovery time due to the TX pulse's energy.  After appropriate delay the RX and LDC1000 are again allowed to operate and the remaining eddy currents would influence the RX coil.  This way you could have higher energy TX pulses and perhaps higher energy target RX signals to influence the LDC1000 tank circuit.  It depends I guess on the recovery time of the RX after blanking.  Do you have an idea of what this time would be?  It should be similar to a situation where you would be switching between a coil matrix. 

This is a brief description of the idea:

http://www.ndt-ed.org/EducationResources/CommunityCollege/EddyCurrents/AdvancedTechniques/background.htm