NE555's link On the Basket Coil Google Translated. I tried to post the whole page but HTML links are not supported.
Basketware sensor detector
Koschey-5I / MI
Among the fans of pulse metal detectors basketware sensors use a well-deserved fame. It is with their help it is possible to obtain a record depth for the detection of small objects the size of a coin. Design features such sensors allow to obtain the depth of the target detection gains of up to 20% over the comparable "normal" sensor.
Let us briefly examine the physical processes in place to achieve this growth. In a conventional sensor coil wire is wound turn to turn. With this sensor has a winding interturn parasitic capacitance of the order of hundreds of pF. This capacity is delaying the transition process, caused by the momentum of self-induction, about 10-30mks. It is in such a range is necessary to expose the signal processing delay (main delay in the foreign terminology) in a pulse metal detector. Basketware probe is wound in a special way that minimizes the inter-track capacity. For this purpose, the windings are spread in the space and are arranged at an angle to each other. The typical capacity of a basket Winding sensor is within tens of pF. When such a container does not exceed the transient microseconds, which allows a device to generate "early" signal processing on the purpose and the result - gain in the sensitivity.
At the time, we have developed a couple of designs basketware sensors for our earlier pulse detectors. In this article, we want to offer another new design, which can be mounted in a universal plastic case , a commercially available.
This body has enough cavity bounded by the sensor coil, so winding method "on a bed of nails" used in our previous developments, here is not very suitable. Here we need to wind a special bearing mandrel made of thin sheet material (0.7-1.5mm). It may be, for example, glass fiber, getinaks or, in extreme cases, even thick cardboard. Plans need to download the plug here , and then print the file on a scale of 1: 1 and pasted on a sheet of plastic. Then, using a jigsaw (Needle, scissors, drills) have to cut the ring with the slots, according to the figure. The width of the grooves of about 2mm.
Then proceed to the winding of the sensor coil. For this we need about 20 meters of enamelled winding wire diameter of 0.63mm. For the convenience of the winding wire is desirable to pre-wound on the shuttle 15-20cm long or short coil of suitable size. When rewinding the wire on the spool or shuttle - it is necessary to make sure that the wire is not twisted, is not subjected to strong bending, did not form a small loop is tightened. Winding principle is shown in the figure below. The wire need to twist around the mandrel by laying it into the slots. The number of slots is chosen so that in five complete turns fills all grooves and wire "comes" at the starting point of winding layers. In this case, you need to make the transition to the adjacent groove and start to wind the next layer. All you need to wind the coils 30 or 6 layers for 5 turns.
The result is approximately the winding.
Next, assemble the winding inside the sensor housing. Further assembly and connection follows the same procedure as for the conventional sensor. The only difference - for proper recognition Koshcheev-5I / MI a basket sensor connector is necessary to solder resistor 30kOm. In this case the profiles are activated 3.x which by default are set to basketry and other experimental sensors. For more information about this is written here
After assembly, connect the sensor to the metal detector Koschey-5I or Koschey-5IM and check the operation.
conclusions
The following parameters were obtained in laboratory testing:
Winding Inductance - 317mkGn.
Winding capacity - 80 pF.
Winding resistance - 1 ohm.
Detection range 5kop USSR coins - 31cm.
Thus, we see that by reducing the interturn capacitance and the correct settings in the metal detector (the possibility of setting - an important feature Koschey-5I / MI) received a very real increase in the depth of the detection target. However, it should be noted that this sensitivity was obtained for the air. In the real ground win a basket of the sensor may not be as significant. Everything will depend on the degree of mineralization in a specific area - for example, in the sandy soil depth is more in black soil - less. The fact that a decrease in processing delay, unfortunately, besides increasing overall sensitivity, and increases sensitivity to soil.
Separately, we want to draw attention to the fact that the struggle for interturn capacity reduction is not justified in each sensor. For example, we sometimes ask - and it would be good to do "deep basket-gauge" size 1h1m or 2h2m J. The answer - it is absolutely unjustified. The point is that when working with a depth sensor device is specially configured to work with large processing delays. This is to reduce the sensitivity to the ground, and small targets. Therefore, there is no sense to fight for the reduction of the duration of the transition process, as the processing delay it significantly exceeds.
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