My Search Programs for Minelab E-Trac & CTX 3030 Metal Detectors
SEARCH PROGRAM #1: Level 1 - "High Discrimination/Low Noise", page 3
Program Settings: SENSITIVITY MENU
SENSITIVITY - AUTO (pages 54-56 of the E-Trac Instruction Manual)
With this setting, the Sensitivity level is just a little above the 'Suggested' Sensitivity level.
SENSITIVITY - AUTO (page 21 of the CTX-3030 Instruction Manual)
Auto Sensitivity level is shown by the white number (left number) on the Sensitivity Panel optionally displayed at the bottom center of the Smartfind-2 window (pages 19, 21, and 46 of the Instruction Manual). If Manual Sensitivity is ON, this number will also represent its level that you have set. The green number on the right of the Sensitivity Panel shows the 'Suggested' Sensitivity level.
Do not use Auto Sensitivity at the beach.
Unless I metal detect on the low-mineralized or NEUTRAL ground, I do not use Manual Sensitivity to allow the detector to respond to deeper and small targets lying within detecting range. Instead, I utilize less discrimination and receive more signals, most of them being true signals emitted by the accepted targets. This way I can "see" what lies underground and avoid being bugged by false signals caused by iron junk and/or high mineralization. Also, when I compared these two approaches to increasing the detector's "sensitivity", "Maximizing Manual Sensitivity" and "Lowering Discrimination", through testing, the latter gave me greater results in the high-mineralized ground.
In AUTO mode, E-Trac (or CTX-3030) continually analyses the ground and adjusts the Sensitivity level when the ground mineralization level changes. One should keep in mind that the ground mineralization level changes more often (sporadic mineralization) at the former settlement sites located in the never-plowed areas than at the sites located in the plowed fields (where all cultural layers and "mineral pockets" have been uniformly mixed up).
So when you hunt in the never-plowed area, you should always run your E-Trac (or CTX-3030) in Auto Sensitivity to avoid jamming its microprocessor, which will cause a substantial loss in operational depth range. To learn how the Sensitivity settings affect the detector's performance, read about it on page 1 of my article - How To Search Around Cellar Holes Successfully.
If you hunt in the plowed fields, and the ground is not highly mineralized, and the area has been cleaned of most superficial junk (and good targets), and you wish to switch Sensitivity to Manual (page 56 of the E-Trac Instruction Manual, page 21 of the CTX-3030 Instruction Manual), the 'Suggested' Sensitivity should be used as a guide in setting the Manual Sensitivity.
To get more detecting range while hunting in areas with low trash, Manual Sensitivity should be set in the 23-25 range for so-called "depth boost" to come into effect. However, if the medium-to-high levels of mineral content in soil do not permit utilization of Manual Sensitivity setting above 23, and you still set the Manual Sensitivity much higher above that point, you will risk running your detector not being properly adjusted to the current metal detecting conditions.
Also, with Sensitivity being set too high, correct identification of target properties is negatively affected by instability, in particular, of Fe numbers in the target's FE-CO read-outs. Especially this concerns identification of deep coins lying close to iron objects. In this case, the Fe value of a deep coin may bounce within the Fe 17-27 range, sometimes reaching even higher numbers, when the coin's signal gets affected by nearby iron junk. This is why the Fe values are not considered reliable and should not be used for identification of deep coins. In the same case, the Conductivity values are more stable and must play a major role in determining the non-ferrous target properties (read more details on questionable signals here).
You can also adjust Manual Sensitivity to the highest level of stability through manual selection of a channel with the least noise (page 75 of the E-Trac Instruction Manual, page 20 of the CTX-3030 Instruction Manual). However, if you set all three internal signal channels to the same high level, the magnetic ground interference may cause false signals and unstable Target ID (the FE-CO numbers will be bouncing all over the Smartfind window). Also, in Auto Sensitivity, any Minelab's FBS detector is able to detect at a higher sensitivity level than you are able to achieve for the same noise level.
The Manual Sensitivity can be effectively used for gaining more operational depth range only when:
1) the ground is NEUTRAL or has a very little mineral content;
2) the iron junk is sparse in the ground;
3) stable audio Threshold can be maintained;
4) you metal detect in the grass-overgrown area, and you do not have a larger search coil, and increasing the Manual sensitivity is the only way to get to shallow coins and artifacts;
In any case, remember that an amount of deep targets to which the detector is allowed to respond is inversely proportional to the Discrimination level - a key factor unlike Manual Sensitivity.
AUTO SENSITIVITY LEVEL - A (page 55 of the E-Trac Instruction Manual)
AUTO SENSITIVITY LEVEL - A (page 21 of the CTX-3030 Instruction Manual)
The Auto Sensitivity Level allows you to be more conservative or aggressive while operating the CTX-3030 in AUTO Sensitivity. Increasing this level by +1, +2, or +3 sets the Auto Sensitivity higher on each of three internal signal channels (high, medium, and low - all helping identify targets correctly) than the automatic setting by the number of levels you select. However, increasing this level will also cause a few more false signals and decrease the accuracy of Target ID's. Decreasing this level by -1, -2, or -3 will have opposite effects on performance of your CTX-3030.
Some detectorists utilize level "+3" to detect faint target signals, but it is a "catch-22" as more false signals will appear. And certain types of small and thin hammered coins are left undetected when the "+3" level is used because of affects of high mineralization. The "A" setting allows me to find not only the smallest hammered coins of 5mm in diameter, but also tiny fragments of other hammered and thin milled coins.