I only brought up my personal issues because there will be people who will probably attack me much like they do Dave Emery since I haven't brought out my concept. I have made a statement of what I feel I can do but since I haven't done so, I fully expect flack. Personally, now I don't care either way since I answer to no one now. Whether I even complete the project is something I can't answer at this time. The loss of my significant other right after the death of my father was the last straw for me.
Now, as for the question about a drawing program to draw a spiral coil, personally, I don't know of one. I don't use spiral coils. Instead, I find I can get the response and depth from a conventionally built coil using Teflon coated wire to help with the coil speed concerns.
For those of you trying for the earliest sampling time, there is a relationship between the coil design and the damping resistor that few fully realize. Build a coil using Teflon coated wire and it is quite possible one can increase the size of the damping resistor. This combination can and usually will result in a faster dampening of the decay signal.
Leave the damping resistor the same but use Teflon coated wire may not show any improvement and in some cases may actually appear to be slower. I won't go into the details as to why this happens but I did experiment and prove it can happen.
Now, change the insulation or stated differently, the voltage rating of the Teflon wire and again, you change the coil dynamics. In other words, a coil made with 1000V insulation rating may require a larger valued damping resistor to obtain the best results.
So, how does this help determining gold from ferrous junk? Well, I won't divulge some tricks I did some time back that allowed me to determine small thin ferrous junk from gold, but I will say sampling earlier and later and looking at the signals will help. At least it does for certain types of ferrous junk.
Here are a couple of things to keep in mind. First, ferrous signals are much stronger than gold signals for corresponding similar size objects. Generally, gold responses are mellow when compared to ferrous signals. When using a mono coil, ferrous objects can easily generate a double blip type response, especially if the ferrous junk is long and narrow such as a boby pin or a nail. Gold, as a general rule will not do that.
If a ground balancing detector is designed that is similar to the TDI, then gold will usually have a repeatable level at which it is nulled or balanced out. Ferrous junk can vary as you move around the object to make your analysis.
Now, these are a few obvious observations. Others can be found and should be looked for by the operator of the detector. Be careful when first learning because what might appear to be true often isn't.
Reg
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