Metal Detector
(630-3003)
Operation
Faxback Doc. # 6275
The steps in this section explain each control on the control housing and handle, and how to use your metal detector. Take a moment to become familiar with the position and use of the controls before using the metal detector. THE VIEWMETER The view meter is located at the top of the control housing and measures battery power, determines the quality of hidden metal, and helps you tune the detector. Turning On the Detector Hold the detector in a position comfortable for you, then turn it on by rotating VOLUME two-thirds clockwise. Set TEST to NOR to detect. Adjusting the Controls in the Field The tuning skills you will learn while preparing the detector will be put to good use during your actual search. You will know how each control works so you can fine-tune the detector quickly. If you wish to test the accuracy of your tuning at your current location in the field, take a few samples of different kinds of metal with you. Note that some metals, when left exposed to the elements, become corroded; so, it is always wise to carry along a piece of corroded metal. TUNING THE DETECTOR Setting TUNE The Radio Shack VLF Discriminator Metal Detector distinguishes between ferrous and non-ferrous metals. When the detector senses a metallic object, one of two reactions occurs - the sound and meter reading increase or decrease. The result depends upon the type of metallic material, ferrous or non-ferrous. Ferrous metals contain iron. Gold silver, copper, platinum, aluminum, lead, zinc, etc. are examples of non-ferrous metals. TUNE fine-tunes the balance between the detector's receiver and transmitter circuitry. Follow these steps to set TUNE. 1.
Rotate VOLUME two-thirds clockwise.
2.
Set MODE to VLF.
3.
Set TEST to NOR.
4.
Set the remaining controls to mid-range.
5.
Hold the search coil up in the air, press and hold down Auto-Tune, and slowly turn TUNE. The pointer swings back and forth and the detector sounds a tone. Turn TUNE until the pointer rests at or near the center. Release Auto-Tune.
Note:
Press Auto-Tune during operation to automatically return the
pointer to the center. Setting MODE Set MODE to VLF when you use GROUND (See "Setting GROUND). Set MODE to TR1 or TR2 when you use DISCRIMINATOR (See "Setting DISCRIMINATOR)". Using GROUND helps tune out false signals from mineralized soil. DISCRIMINATOR distinguishes between NON-FERROUS and FERROUS objects. Setting SENSITIVITY To adjust the search coil's ability to detect objects at different depths in the soil, rotate SENSITIVITY from MIN to MAX. For maximum performance, set SENSITIVITY as high as possible. If the detector makes a "Chattering noise, decrease SENSITIVITY until the "Chatter" stops. Setting GROUND GROUND tunes out false signals from mineralized soil. Follow these steps to set GROUND. 1.
Set MODE to VLF and lower the search coil to 1/2- to 2 - inches above the ground.
2.
If the pointer swings to the left, turn GROUND to the right.
3.
Raise the search coil and press Auto-Tune. the center.
4.
Repeat Steps 1-3 until there is a very small variation in the meter reading each time you lower the search coil to the ground.
The pointer returns to
Notes: Setting GROUND takes a little time, but is critical for accurate operation. After you set GROUND, do not reset it until you use the detector at a different site. Setting DISCRIMINATOR DISCRIMINATOR determines whether the hidden metal is NON-FERROUS or FERROUS. Before you set DISCRIMINATOR, you must set MODE. Set MODE to TR1 to detect extreme differences in metals, such as between iron and gold. MODE to TR2 to detect even greater distinction between metals.
Set
Set DISCRIMINATOR to mid-range. While you detect, adjust DISCRIMINATOR to the best position. The difference between iron and gold shows on the meter (iron in the ferrous section, gold in the non-ferrous section). As you set DISCRIMINATOR higher, the detector becomes more sensitive to the differences between aluminum and gold, but some small pieces of valuable jewelry, such as small rings, may be over-looked. Therefore, coin collectors do not usually set DISCRIMINATOR higher.
Also, it first rejects small pieces of silver paper, then thick foil, and finally metal objects like pull tabs from aluminum cans. Notes: Each time you use the detector, you must adjust DISCRIMINATOR. expedition presents new challenges.
Each
Press Auto-Tune during operation to automatically return the pointer to the center. Fine-Tuning the Controls Set these controls: 1. 2.
TEST to NOR MODE to VLF
Set the remaining controls to mid range. When you detect metal, switch MODE between TR1 and TR2 to determine the quality of metal. Adjust all remaining controls to their desired positions. (See "Tuning the Detector.") SWEEPING HINTS Keep the search coil in a consultant parallel position to the ground throughout the sweep. Move the search coil slowly from side to side, covering about a 3-foot area, overlapping each sweep. The threshold tone should peak as you pass the target center. (Hurrying will cause you to miss targets.) Note:
The search coil will not detect without motion.
Be careful not to swing the search coil upward at the end of each sweep. The swing up can cause the detector to emit false signals. Keep the search coil parallel to the ground at all times but don't touch the ground. Hitting the ground may cause a false signal. DETECTION HINTS No detector is 100 percent accurate. adversely influence metal detection. things:
Various conditions and objects may Its reaction depends on a number of
The angle at which the object rests in the ground The depth of the object The amount of iron in the object The size of the object To pinpoint an object, the second time, go at right angles to the first time, making an "X" pattern. Note:
The target will be directly below the "X" at the point of the loudest response.
This allows you to detect some targets that were hidden the first time
due to the sweep direction. If trash in an area is so heavy that you get false signals, slow your sweep speed and use shorter sweeps. Notes: A good detection has a consistent rise and drop of threshold tone. A poor detection has irregular highs and lows in threshold tones. If the metal is in the shape of a circle, opposite reactions may occur. A good target response repeats as you swing the search coil over the suspected target. Trash-induced signals tend to not repeat. Recently buried coins might not respond the same as coins buried for a long period of time. Some nails, nuts, bolts, and other iron objects (such as old bottle caps) oxidize and create a halo effect around these objects. A halo effect is caused by a mixture of natural elements in the ground and the oxidization created by different metals. Because of the metal mixtures, target signals may not be in a "fixed" position. This effect makes these objects very hard to reject. (See "Fine Tuning the Controls.") TONE VARIATIONS The threshold tone may vary slightly while you search due to soil changes. This does not usually affect the sensitivity of the unit and should not require further adjustment. If the threshold tone changes significantly, you might need to readjust GROUND. Sometimes the change in threshold tone is due to reasons other than ground conditions and can be easily corrected by a simple procedure. Raise the search coil one foot from the ground and push Auto-Tune. Lower the search coil to the ground again. If this does not correct the problem, repeat the full procedure to set GROUND. (See "Setting GROUND.") If you continue to have problems, contact your local Radio Shack store for assistance. (BR/smc-05/09/94)
