Tweet
Test of metaldetectors specialized of coin searching (IB system )
Test objects
1.Coins with size approximately 0,3 ; 0,2 ; 1 ; 2 inches
2.Aluminium sheet with diameter approximately 3,5 inches
3.Ferrous sheet with letter size
4.Aluminium sheet with letter size ( approx. 29 x 21 cm. )
5.A nail with length approx. 3 inches
6.Ceramic plate ticker approx. 2 inches (ceramic with high losses- giwes reacrion to detectors)
7.Hot rocks bigger than 3x3 inches ( neodymium magnet need to stick poorly to them ! )
9.neodimium magnet
Tests
1.Test ,, Mechanical instability of the search head “- some detectors hawe problems with parasitic signals, noises ,caused by the insufficient hardness of the search head . Some of them are caused by the connection of the search head to the rod .
2.Test ,,overload “ .We will test the electronics how to hold the overload from hot rocks.
-sensitive of the detector is estabilished on 70% ; check the distance from which the target still giwes reaction .On distance 1 inch place a hot rock with size bigger then radius of the search head and thickness approx. 2-3 inches .A good detector do not have losses of sensitivity despite presence of the hot rock in the front of the head .Low quality equipment will loses depth or ,, blocking “.
3.Test ,,dynamic characteristics” (speed of reaction , recovery speed - how much the detector is agile ,zippy ).A good detector will find coins even on a lot of garbage terrains .
Test procedure A : - on wooden plate attach a coin approx. 1 inch diameter and ferrous nail ,distance between them is approximately equal to the radius of search head .A good detector will react of the coin ,when it passes first.
Test procedure B : - cheking if the detector have a reaction to the coin , if it is attached behind hot rock or ceramic plate . The test is comparative -larger coins are easier to detect . the stronger it sticks magnet to the hot rock , the worse the coin is detected.
The depth of discrimination strongly depends on the type of soil . In most cases, the depth of relative true discrimination does not exceed the diameter of the search head. When working on heavy mineralization ( pure magnetite ) discrimination is impossible .
7.Autotracing –high mineralized stone is placed in front of search head for more than 7 seconds.After that the stone is put away very quicly.The good systems for automatic ground balance with autotracking do not have problems with this test.
8.Test ,,very close coins’’ -coins with different sizes are moving on a distance from 0,3 to 3 inches from the search head through its entire area with different speeds.Some detectors have a serious problems with this test.
9.Test ,,ground noise “ – detector must be in ,,pin point “ mode ,or slow motion mode. Adjustment of the ground rejection must be done near surface of the soil .Test results for good detectors are as follows : close to soil surface –neutral ground effect, far from soil surface ( on distance more than the diameter of the search head )- slight positive ground effect.Test results for not so good detectors are with very big variations of the ground effect ,depending of the distance of the search head to the ground.
12. Relative sensitivity to hoard (coins in a ceramic pot ) . Detectors with a working frequency higher than approx. 8 kHz have noticeably worse results of this test .
The tests were written about 18 years ago. Then expensive models they had ground balance system with autotrack . We were digging holes in the soil , at the bottom of which we set the targets . This is wrong, but we did not know , that even thoroughly filled with the same soil hole ,, , amplifies “the coin signal, for example . Monte’s nail board test was very difficult or impossible for most detectors . we did not even think for soaking the soil with salt water and the placement of ceramics , hot rocks and coins below them -An extremely difficult test, on which even now very little detectors can perform well…
Test objects
1.Coins with size approximately 0,3 ; 0,2 ; 1 ; 2 inches
2.Aluminium sheet with diameter approximately 3,5 inches
3.Ferrous sheet with letter size
4.Aluminium sheet with letter size ( approx. 29 x 21 cm. )
5.A nail with length approx. 3 inches
6.Ceramic plate ticker approx. 2 inches (ceramic with high losses- giwes reacrion to detectors)
7.Hot rocks bigger than 3x3 inches ( neodymium magnet need to stick poorly to them ! )
- Ceramic pot full of coins , dimensions – diameter approx. 10 cm , height approx. 11 cm . Coins must be covered with paint or tape , So there is no electrical contact between them .
9.neodimium magnet
Tests
1.Test ,, Mechanical instability of the search head “- some detectors hawe problems with parasitic signals, noises ,caused by the insufficient hardness of the search head . Some of them are caused by the connection of the search head to the rod .
2.Test ,,overload “ .We will test the electronics how to hold the overload from hot rocks.
-sensitive of the detector is estabilished on 70% ; check the distance from which the target still giwes reaction .On distance 1 inch place a hot rock with size bigger then radius of the search head and thickness approx. 2-3 inches .A good detector do not have losses of sensitivity despite presence of the hot rock in the front of the head .Low quality equipment will loses depth or ,, blocking “.
3.Test ,,dynamic characteristics” (speed of reaction , recovery speed - how much the detector is agile ,zippy ).A good detector will find coins even on a lot of garbage terrains .
Test procedure A : - on wooden plate attach a coin approx. 1 inch diameter and ferrous nail ,distance between them is approximately equal to the radius of search head .A good detector will react of the coin ,when it passes first.
Test procedure B : - cheking if the detector have a reaction to the coin , if it is attached behind hot rock or ceramic plate . The test is comparative -larger coins are easier to detect . the stronger it sticks magnet to the hot rock , the worse the coin is detected.
- Noise resistance . Detector capability to remove the interference from power lines .
- Sensitivity of the detector to coins perpendicular to the the plane of the search head.
- Depth of discrimination . It is checked from what distance it starts to reject the iron nail.
The depth of discrimination strongly depends on the type of soil . In most cases, the depth of relative true discrimination does not exceed the diameter of the search head. When working on heavy mineralization ( pure magnetite ) discrimination is impossible .
7.Autotracing –high mineralized stone is placed in front of search head for more than 7 seconds.After that the stone is put away very quicly.The good systems for automatic ground balance with autotracking do not have problems with this test.
8.Test ,,very close coins’’ -coins with different sizes are moving on a distance from 0,3 to 3 inches from the search head through its entire area with different speeds.Some detectors have a serious problems with this test.
9.Test ,,ground noise “ – detector must be in ,,pin point “ mode ,or slow motion mode. Adjustment of the ground rejection must be done near surface of the soil .Test results for good detectors are as follows : close to soil surface –neutral ground effect, far from soil surface ( on distance more than the diameter of the search head )- slight positive ground effect.Test results for not so good detectors are with very big variations of the ground effect ,depending of the distance of the search head to the ground.
- Dependence of sensitivity from the passage speed of the targets in front of search head.
- Differential sensitivity . Detector capability to react well both small and large targets . For this we must have with coins of copper-nickel alloy with a diameter of less than 12 mm , large copper and silver coins , and with a tray or sheet of forged copper with a diameter greater than 25 cm .
12. Relative sensitivity to hoard (coins in a ceramic pot ) . Detectors with a working frequency higher than approx. 8 kHz have noticeably worse results of this test .
- Discrimination of an iron object with a large area , for example, a can or iron sheet bigger than 10x 10cm.
- Coin under a mound ( pile ) of soil . the test is done with mound high 5-7 cm.
- Ergonomics -type of stick ( S- shape With a separate handle at least they tire the hand ). Center of gravity of detector . The presence of a pointer-operated lever makes the detector more operational .
The tests were written about 18 years ago. Then expensive models they had ground balance system with autotrack . We were digging holes in the soil , at the bottom of which we set the targets . This is wrong, but we did not know , that even thoroughly filled with the same soil hole ,, , amplifies “the coin signal, for example . Monte’s nail board test was very difficult or impossible for most detectors . we did not even think for soaking the soil with salt water and the placement of ceramics , hot rocks and coins below them -An extremely difficult test, on which even now very little detectors can perform well…
Comment