Why is discrimination the enemy of the Seeker? I will try to explain it using the top model of the Minelab Manticore detector. Why choose the most expensive equipment possible that most of us cannot afford? There are a few reasons. First of all, this detector has great imaging and you can easily understand everything by looking at the screen. Moreover, masked targets are very easy to spot if something is lying close to the iron.
Apart from discrimination, we can set the so-called iron limits and Ferrous limits. What does it do? The iron scale is wide in this detector, which cannot be said about other devices. What does it do? It is easy to distinguish and separate large and fine iron from each other.
What’s the point of all this? For a simple reason, big irons are often very interesting. A horseshoe, a sword, a cannonball, a bayonet can be the find of the day, and a well-identified bottle cap can save you time.
Ok, let’s start with the basics.
The upper gray bar is the set range of iron – the fine one. In this case, we have an iron nail. The bottom bar is for larger items. The axis in the middle is the conductivity axis from left to right from ID values 1 to 99.
For example, a thin silver coin will be in the middle on the left, but it may also fall… depending on the conditions there…
To be sure, we rotate each target 90 degrees and check how the drawing of the object has changed… this is a really big hint!
Here is the same nail after turning 90 degrees. Why is this happening? Often, iron, especially when rusty and having various complex shapes, distorts its color. In the case of forged nails, it may be their heads or the bend itself. The round and hollow shapes of the target are a story for another article.
The image above shows EMI interference. Just detune the detector or lower the sensitivity.
Here the nail or steel screw can be seen to be on the verge of the upper limit range. What do we do to check? We focus on the goal. Then the object will disappear or completely fall into the upper zone of the range.
A silver-struck coin with a range at the bottom of the ID scale. Low conductor, petty and miserable medieval silver. Please note this type of target may fall into the low end of the iron limit under certain conditions.
Przykład monety maskowanej przez mocno zmineralizowany grunt.
Here’s a coin next to a nail. You can see the signal of an iron object trying to cover the coin’s signature.
Finally, how not to set limits. A textbook example of how not to do it is below. This is an error that closes the device’s potential and does not allow separately masked objects. The detector becomes blind if the coin is next to the iron and there is no chance of separating and identifying it. This setting improves work comfort and silences the device… but only apparently. Moving too close to the axis seems like an ideal solution, but it is not! We have the Silencer option, which also needs to be used carefully.
So how do you set both limits? Under the conditions prevailing in a given place and the lowest – in the sense of the smallest value away from the conductivity axis. If the manufacturer sets the upper limit to 9, try starting with a value of 7 or lower. In my case, the limit is 4 even in difficult conditions. This arrangement places a greater workload on the operator, but also drastically improves the device’s performance.
There is no silver bullet here. You have to exercise until it hurts. Finally, there is the All Metal mode and the complete opening of iron and discrimination limits to check the given object.