I also inquired about this several months ago and got some good info from Dick at the Minelab Depot in Las Vegas. I personally have not put these settings in so I cannot tell you how well this works. Program it and save it and you will have it in memory.
Here is the email he sent me on the XS.
Today I brought in a couple of my small test nuggets that measure approx. 3 mm. or so. These two weigh approx. 2/10 ths of a gram and 3/10 ths of a gram, by the way. I have an Explorer XS sitting here beside my desk and I can get the best response from a nugget this small by turning the Iron Mask control all the way down to a level of -16. Also, By going into Learn Mode, temporarily blacking out the target box, then steering around the screen until we blacked out the entire screen except for a narrow band the height of the cursor box (leaving the screen all black except for the white band across the entire bottom of the target screen where small, low conductivity nuggets will always appear), then returning the target box to white. I had the detector set up as follows:
1. Sensitivity : 19 or 20 (in the field, set this as high as possible without chattering/going unstable)
2. 2. Iron Mask : -16
3. 3. Don't forget to hit the Noise Cancel button periodically (this is very important !!)
4. 4. Always wear headphones so you can hear these small target sounds better
5. 5. Use the large Target Box - both to black out the screen, and while searching
6. You will eliminate lots of junk iron, nails, etc. with all the top 3/4 ths of the screen blacked out, but you will still pick up small bits of lead shot, etc. because they read almost exactly like a small nugget, which will be right at the bottom of the target screen. The two tiny nuggets I brought in today were both found with my XT17000 in the Arizona desert this past winter, by the way. This is a machine that is optimized for gold nugget hunting, not an all-around coin, relic, etc. machine like the Explorer. So, realistically, you could expect to be able to detect a small nugget anywhere from the surface to a several inches deep, depending on the level of mineralization in the soil, exactly how deep it actually is, the shape and cross-sectional area of the nugget, the relative moisture level of the soil at the time, and a number of other variables. So perhaps you can begin to see why no one can say exactly how deep a particular machine will go on a particular nugget on any given day. However, these are just some general guidelines from my own personal experience in nugget detecting out here in the desert,
