Understanding signal response graph, sensitivity and threshold

[OBXmetalDet]

Hi,

I have a few questions.

1. Suppose I use a single frequency of 20kHz. If I do that, would I be able to detect only certain metals or would the detector still pick up all metals? If it would still pick up all metals, would the signals from some of those
metals be weaker (quieter) than other metals?
2. What exactly is threshold? What exactly are you filtering out?
3. When you increase/decrease the sensitivity, what exactly is being changed? Are you making changes in the frequency or something else?
4. In the attached signal response graph, what are the units on the X and Y axis?

 

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[Terry Soloman]

The high 20kHz frequency is good for very small, shallow targets, like natural gold nuggets. It will also find coins and other metals. A lower frequency, anywhere from 3kHz - 12kHz, is desired for "Coinshooting," because the lower frequency gives added depth on coin-size targets. An audible Threshold, is a steady hum from your headphones that acts as an audible guide. A slight, almost unperceived rise in threshold sound can be an indication your coil is over a deep target, this is called a "positive break," in threshold. A "negative break," in the threshold is momentary silence when the coil passes over a target. This is also an indicator of a deep target. Think of Sensitivity as "Gain," on a CB radio. You are fine tuning the frequency to its maximum potential - BUT, too much gain or, sensitivity, can actually decrease your depth in highly mineralized soils, so study up on this subject. Good Luck and Big Gold!