Written by te TreasureGuide for the exclusive use of the Treasure Beaches Report.
Not too long ago I talked about using a non-motion or pinpoint mode rather than a motion or discrimination mode as a primary search mode. I wanted to expand on that some.
First, some background is necessary. There is not a perfect relationship between the perceived or psychological loudness of an auditory signal and the decibels actually produced by a metal detector. Generally, there will be good a relationship, but not a perfect one. A person who has hearing loss in a particular range of frequencies, for example, would be one example of how that relationship would be imperfect.
The above chart is an adaptation of a chart that I used before for another purpose. I think it will be helpful even if not totally precise or accurate.
On the vertical dimension is both loudness and pitch of the detector signal. Using the Equinox in pinpoint mode as the example, there is a correlation between signal strength and the signal pitch. In pinpoint mode as you move the coil closer to the target, the signal will become louder AND get higher in pitch. I don't have the instrumentation to measure the decibels or frequency of the signals, but that is how I hear it. The signal increases in strength (loudness) and pitch until the coil right over the target, which is when the signal is loudest.
That is different than when you use a motion mode. In discrimination mode you will perceive signals as being more of a binary event - on or off. The signal might be more complex, but I think that is how you will experience it. It will be perceived as a discrete signal as shown in the illustration below.
If you swing your coil too fast in non-motion mode, you'll be cutting down the duration of the signal and possibly also the strength or loudness, and you'll be losing depth and sensitivity to small or deeper and defeat the purpose of using a non-motion mode as a primary search mode.
The perceived signal to three separated targets of different size and/or depth when using a motion mode will be perceived as three discrete signals rather than overlapping signals as shown in the illustration at the top of the post.
It you use a good slow sweep speed in non-motion mode, the signal duration will be longer and the pitch and loudness will vary, as shown in the first illustration. In motion or discrimination mode you'll be receiving a signal after the detector has done some processing. The metal detector, will in effect, sum up the input and give you processed output that will give you vary the pitch to give you information about the type of target (depending upon your detector settings) as well as a conductivity number or target ID. The pitch or frequency of the signal will not reflect how close the coil is to the target, but rather the nature of the target. You might think of the signal received in non-motion mode as being like analog output rather than a digital output. You have to do some of the processing that the metal detector would otherwise do, but you get other information. You won't get the target ID information, but with some practice you will often be able to tell something about the target depth and shape from the non-motion mode signal. I prefer the non-motion mode.
While many detectors will work very much like the Equinox, you will find some differences with other metal detectors. For example the Garrett Ace in pinpoint mode only gets louder as you get closer to the target. It does not produce the correlated increase in signal frequency that you get with the Equinox.
At this point, I'll point out that in a non-motion mode, you can have overlapping target signals, something like shown in the first illustration. I'll have to explain more about that some other time, but you can be getting a signal from black sand, for example, but still hear a signal from a coin in the black sand. The black sand will produce a broader signal, something like the low purple line in the first illustration, but then you will also get a sharper signal that will stand out, something like the signal illustrated by the dark blue line in the same illustration.
This discussion will be most useful for those who generally use a discrimination mode.
I know this discussion is sloppy and imprecise, but I'm trying to make it simple, and it is not really all that simple.
That is all for now. I'll have to continue with this discussion some other time.
If I was confusing or inaccurate, let me know how and I'll try to clarify or correct. I know I was not totally correct in many ways. Again, trying to simplify.
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Source: MagicSeaWeed.com. |
The surf is not real big. I'm hoping we'll get some more winter weather this year. Otherwise we could be in for a very long summer.
The tides are not too big n ow.
I have a lot of cleaning to do on recent finds. Also research.
Good hunting,
Treasureguide@comcast.net
