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Date Posted: 17:25:25 07/07/02 Sun
Author: Ralph
Subject: Iron ID vs. Discrimination
In reply to: Minelabmayer 's message, "Iron discrimination" on 21:17:06 07/05/02 Fri

Iron I.D. and true phase shift discrimination are two very different things to begin with.

With Iron I.D., the object is to have the machine simply "identify" the possiblity of a target signal being ferrous or iron material without actually removing the signal response from the audio processing.

On the other hand, full-range discrimination was developed with the intentions of being able to eliminate the signals of certain levels of relative conductivity from the detectors audio. While the machine still "sees" these objects, and knows they are under the coil, they are simply eliminated from the operators "perception" if you will......you don't hear them, so don't know they are there.

Most iron I.D. circuits operate in a manner that help them retain most of their depth ability, right along with the all-metal detection circuits. The I.D. circuit never actually "eliminates" the signal of the iron object, but rather "identifies" it by the addition of a certain tone or response. However, in using true discrimination circuits, no matter the level of discrimination used, you are almost guaranteed to be losing some percentage of maximum depth capabilities due to the simple fact that it takes more signal to process for discrimination than for raw detection depth alone.

Where true discrimination circuits on gold machines are concerned, the real problem is in "target masking", and can be created via different routes. For example, most current motion-based discrimination machines operate in such a manner that they take an average reading of the background matrix during the sweep of the coil, and any true metallic target is easily seen within this matrix as a "target" to the machine. The discrimination circuits act as their own "ground balancing" function if you will, eliminating the lowest levels of "normal" ground mineralization.

But a problem you can expect with hunting small or faint gold signals with a discrimination type detector is where higher levels of ground mineralization are present, the ground itself can be of sufficient conductive or magnetic properties to cause the "masking" or hiding of those same smaller or fainter target signals. Hot rocks, cold stones, and any other "eliminated" target conductivity level when using a discriminating detector can cause the same effect.

While I can appreciate the modern marvels of some of the machines being developed these days along VLF-IB "auto-tracking" lines, and the simplicity in using such machines with good results in some conditions, I've also been at this game alot of years, and understand the pros and cons of auto-trackers vs. manual machines in obtaining the absolute best performance that a machine can provide when things start to get difficult. To date, I still firmly believe that a good manual machine in the hands of someone who understands that machine intimately will obtain better absolute "performance" than any of the automated units out there. But I also understand very well that there are times when the averages are against you when ground coverage comes into play, and a good auto-tracking machine will give you the advantage just as a part of the percentages...... the more ground you cover, the more likely you are to find gold.

Just a few thoughts.....

Ralph

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