Coin on edge problem discussion

[kt315]

still no. if i give the pics ML will patent its right now! no goodies from me for ML!

[Andi68]

Ok kt.
I think I can imagine what you mean and I might become myself
Try to make these coil shapes

[Carl-NC]

When a coil is swept normally (left-right) a coin on edge will respond differently depending on its edge direction and how far it is off-center of the coil.

Case 1: Coin is oriented at 3-9 o'clock
If the coil is swept exactly on-center to the coin there will be very little response because only the edge of the coin sees any of the TX field.
As the coil is moved off-center, the coin begins to respond more strongly. Further off-center, it gets weaker again.

Case 2: Coin is oriented at 12-6 o'clock
If the coil is swept exactly on-center to the coin there will be a double response, on either side of top dead center.
As the coil is moved off-center, the double response gets quicker and weaker.

The reasons for all this is that the TX flux lines are vertical at the center of the coil, but diverge off-center and even become horizontal. Horizontal flux lines can easily couple with a vertical coin, and this happens off-center. Vertical coins are notoriously hard to pinpoint because they are not where they seem to be.

Most detectors will easily show this behavior. I'm guessing the Nox is doing some kind of processing to suppress what it thinks is a bad target. It may be an attempt to suppress bottle caps as a flat-buried bottle cap also had weird off-center behavior.

[Andi68]

2-3 meter sense on goldnugget 1 gram no Problem with the deepers

[kt315]

i tell how to retune delta pulse on 15us delay how decrease strobes 20us and how to increase to 300 Hz frequency. in DP thread.
you get a deeper 70cm on 1 gram gold.

[Koala]

in the video shouldn't you be waving the coin over the toe and heal of the coil as this is where the coin will pinpoint with a DD?


coins on edge null towards the centre of the coil. Same on any DD, same with my IDX


concentric coils are much better as coil on edge is still offset but nowhere near as much. My 1265x gives best response to a coin on edge over the edge of the RX coil which is still within the small plug I dig




the original "feature" was "very large" silver coin on edge detected as iron. The new firmware has improved but not eliminated the problem.


also a stack of 10 or so copper coins on edge weren't detected. I have tried this test with my analogue detectors and there's no problem.

seems like the NOX gets confused by the multi responses and thinks it junk.

[bklein]

Old fw my EQ was pp right in the center (not edge targets though). New fw they say things pp to the left and down. I didnt see a change so maybe my fw load didnt take. Which brings a second question, would a fw load fail and the utility not say so? I would think there would be a checksum test on the new load. Had to do resets using the older code to get out of weird behavior that I didn’t set. Products I worked on in the past check the fw integrity on power up. Isnt that a standard thing to do?