(see also MD 3003)
|Other RadioShack Metal Detectors|
Principle of Operation.
The cct for this metal detector is a simple form of transmitter/receiver with a phase detection system for output indication. The transmitter and receiver ccts are inductively coupled in two coils sealed inside the search loop. You will adjust the controls to inductively balance the receiver cct to the transmitter coil. When a ferrous or non-ferrous metallic object is introduced into the electromagnetic field set up by the transmitter coil, an unbalanced state will result between transmitter and receiver coils. The receiver section detects the unbalanced condition resulting in a change in audio level from the speaker, plus a meter reading.
Detection of ferrous vs non-ferrous metals.
When a metallic object is introduced into the electromagnetic field of the loop, one of two reactions will occur. The result depends entirely on the type of metal; ferrous or non-ferrous. Magnetic lines of force from the field, which cross a metallic object, will induce a secondary electromagnetic field around the object. This secondary field either aids or opposes the main field - depending upon the objects magnetic properties. With two reactions possible (one opposing, one aiding), it stands to reason two different indications are possible from the speaker or on the meter.
Examples of non-ferrous metals are gold, silver, copper, platinum, aluminium, lead, zinc etc. Ferrous metals are those which contain iron in some form.
Thus, after setting the "ferrous/non ferrous" control correctly, you can determine if you are detecting a ferrous or non-ferrous metal object just by interpreting the speaker's sound change an/or the meter reading.
This ability to distinguish between ferrous and non-ferrous metals is a major advantage of your MICRONTA metal detector. As you become an experienced treasure hunter, you'll greatly appreciate this special feature.
1. Open battery compartment lid by pressing with your thumb where shown in figure 1
2. Install 6 type AA penlight batteries in the battery compartment as illustrated in figure 2. Be sure to observe correct polarity.
Snap the lid closed.
Rotate "ferrous/non-ferrous" control to ferrous or non ferrous side (fully
counter clockwise or clockwise)
Turn the unit on with the volume control (rotate away from the off position).
Adjust the volume for the desired level of sound.
To adjust the length of the tube, hold the detector and turn the plastic ring clockwise to release the tube.
Adjust to the desired length.
Turn the plastic ring counter clockwise to tighten.
4. Keep the search coil away from any metal object and adjust the "peak" control to the point where you hear a buzzing sound. Then back off slightly from this setting until a very faint tone is heard. This is the most sensitive setting and will give you a meter reading between 2 and 4.
Note: This adjustment for optimal sensitivity is very important.
You can adjust "ferrous/non ferrous" control up to about 1/3
of a turn, along with peak contral - the result you are after is a meter reading between 2 and 4 (with a fairly faint tone sound).
Adjust volume as desired ( it has no effect on sensitivity).
5. Bring the search coil near the area to be searched. Swivel the search coil as desired so it will be parallel to the surface (tighten the wing nut on the end of the shaft to keep the search coil from rotating or moving. After adjusting the angle of the search coil, you may have to readjust the peak slightly.
6. Sweep back and forth over the surface to be searched. Try to keep the search coil a constant distance above the surface (1/2 - 2" (1 - 5cm) is best). And move in wide sweeping motions.
With the ferrous/non ferrous control set
towards the non ferrous side, coins, silver, gold can be detected by
seeing a decrease in the meter reading and a decrease in loudness.
Ferrous metals will produce an increase in meter reading and an
increase in the loudness of the tone.
If you set the ferrous/non ferrous control to the ferrous side, ferrous metals will produce a decrease in the meter reading and a drop in the level of tone. Non ferrous metals (coins, silver gold etc) will produce an increase in the meter reading and loudness of tone.
Note: This ferrous/non ferrous detection function may not be 100% consistent. The detection reaction depends on a number of things:
Angle at which object rests in the ground
Size of object
Depth of object
Amount of iron in an object Etc
Successful treasure hunters learn through experience.
That statement is worth reading again so do it. Experience and experimenting are the keys to success. Experiment at home (away from metal objects) and then try it out in the back yard.
In noisy areas, use the earphone (plug into the
This automatically disconnects the internal speaker.
For best results.
Keep the search coil at a constant distance
above the search surface.
detection will take place when the object is directly below the centre of
the search coil.
If you adjust peak control for too high a meter
reading, you may get false detection results.
In this case, back off the peak adjustment slightly.
When the sound gets weak, replace the batteries. If you are not going to use the detector for a few weeks, remove the batteries.
This is a very handy electronic instrument - not just for finding buried treasure. Use it to find lost hardware in your lawn or locate pipes behind a wall or under ground.
A final note.
Treasure hunting is a fascinating hobby. But it's more than we can cover in a brief Manuel etc .
There is no greater treasure than peace of mind
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