Chinese name: signal frequency of underground metal detector: 7KHz audio frequency: 450Hz working current:12 dcv "aa" (alkaline) 8X 1.5V overview, development history, main functions, safety inspection, other functions, parts introduction, technical parameters, working principle, debugging operation, metal detector assembly and battery installation. The underground metal detector is made of advanced technology, which has the characteristics of wide detection range, accurate positioning, strong resolution and simple operation. Metal detectors are mainly used to detect and identify buried metal objects. In addition to military applications, it is also widely used in safety inspection, archaeology, exploration and looking for scrap metal. Also known as "iron chip detector", it is a good helper for scrap recycling. The underground metal detector uses sound alarm and instrument display, and the detection depth has a great relationship with the area, shape and weight of the detected metal. Generally speaking, the larger the area, the more the number and the greater the corresponding detection depth. On the contrary, the smaller the area, the less the number and the smaller the corresponding depth. The maximum detection depth listed in the table below is the measurement result of burying an aluminum plate of 20cm * 20cm * 0.5cm in dry soil according to the enterprise standard of products. Buried metal, detected through thick soil layer, is bound to be affected by geological structure. There are various minerals in the stratum, which will also produce the signal of metal detection. The signals of these minerals will mask the signals of metals and cause hallucinations. Anyone who has used an old metal detector has this experience. When the probe approaches mounds, stones and bricks, it will sound an alarm. This phenomenon is called "mineralization reaction". For this reason, the old metal detectors can only detect metals in shallow soil, but can't do anything about metal targets buried deep underground. The underground metal detector is equipped with an advanced earth balance system, which can eliminate the interference of "mineralization reaction" and greatly improve the detection depth and effect of the instrument. In the history of development, the appearance of an underground metal detector product promoted the development of an industry, so the unfamiliar and familiar industry of security inspection began to enter the market. In the past 40 years, the detection technology of metal detectors has undergone several generations of changes. From the initial signal simulation technology to the continuous wave technology to the digital pulse technology used today, the simple magnetic field cutting principle of metal detectors has been introduced into many scientific and technological achievements. Both sensitivity, resolution, detection accuracy and working performance have made a qualitative leap. The application field also extends to many industries with the improvement of product quality. The first underground metal detector in the world was born in 1960. The first underground metal detector in the industrial age is also mainly used in industry and mining, which is a powerful helper to check the purity of minerals and improve efficiency. With the development of society, criminal cases are on the rise. 1970 underground metal detector has been introduced into a new application field-security inspection, which is the prototype of the metal detector door we use today. Its appearance means that human cognition of safety has entered a new era. With the rapid development of aviation industry in the 1970s, the occurrence of hijacking and dangerous incidents made aviation and airport safety gradually paid attention to, so metal detector doors played an important role in screening prohibited items in many airport equipment. Also in the 1970s, due to the appearance of metal detectors in airport security inspection, metal detectors began to be an essential security inspection instrument for exhibitions of large-scale sports games (such as the Olympic Games) and security work of important departments. In 1980s, prison violence cases showed a straight upward trend. How to effectively prevent and prevent violent cases as soon as possible has become the top priority of prison management. While relying on the police to strengthen the management of prisoners, metal detection doors have once again become necessary security equipment for prison management institutions in developed countries such as the United States, Britain and Belgium, resulting in an average of 300 prisoners using a metal detection door for security inspection. At the same time, the "treasure hunt fever" in the west has also made great progress in hand-held and portable underground metal detectors. In the 1990s, the rapidly heating electronic manufacturing industry became the darling of this era. In order to reduce product losses and end the embarrassing situation between employees and companies, large electronic companies have adopted metal detector doors and hand-held metal detectors as sharp tools to manage employee behavior and reduce product losses. So the metal detector has its new role-product anti-theft. 9. After the11incident, anti-terrorism has become an important issue for the international community. Explosions and rampant terrorist activities have made terrorists the targets that the security departments of various countries have vowed to crack down on. At this time, the international community's awareness of "safety precautions" has also been raised to a new height. Affected by the 9. 1 1 incident, all sectors of society strengthened their security arrangements. It is precisely because of this influence that the application field of metal detectors has also successfully penetrated into other industries. With the vigorous development of domestic security industry, the research, development, production and promotion of underground metal detectors have made great progress in the field of security inspection in recent years. Since 2005, the national postgraduate entrance examination has been unified and other important examinations at the provincial, municipal and district levels. In order to prevent cheating with mobile phones and other tools, these examination rooms used a new instrument-metal detector for the first time. This instrument can find the items such as mobile phones and pagers that candidates carry with them, and candidates have to apply for "inspection passes" before entering the examination room. Main functions: security check, quick search by public security criminal department; Detection of metal foreign bodies in raw materials, fuels and foods; Check metal objects in mail and luggage; Exploring underground pipelines and cables; Recycling of scrap metal. Other functions 1. Archaeology, exploration and discovery of buried gold and silver treasures and metal cultural relics. The earth balance line can eliminate the influence of "mineralization reaction" and greatly improve the depth and accuracy of effective detection; 2. It has the function of distinguishing ferrous metals from nonferrous metals; 3. Adopt intelligent operating system; 4. It is packaged with high-strength ABC material, which is light in weight and long in service life; 5. Metal sound can be recognized by headphones. The parts are introduced as shown in the figure on the right, 1. Detection board. 2. Tighten the screws and nuts of the probe disc. Decomposition of underground metal detectors Tu Tu III. The moving part of the probe rod. 4. Locking device for the movable part of the probe rod. 5. Indicate the title. 6. Power indicator light. 7. Power "On-off" switch. 8. Zero button. 9. Detection sensitivity adjustment knob. 10. Identification function adjustment knob. 1 1. Complete machine support. 12. Headphone jack. 13. External power input jack. 14. Adjustment button for ground balance function. 15. Critical sound adjustment button. 16. "Ground Balance-Identification" working mode changeover switch. 17. Input jack of output cable of probe panel of the whole machine. 18. External 1 dry battery box. 19. The nominal maximum detection depth of the product for testing the technical parameters of the small dish is the measurement result of burying a 60 cm *60 cm *0.5 cm aluminum plate in dry soil according to the enterprise standard of the product. Detection depth: the large plate is 3.5 meters (the maximum depth is 5 meters). Detection depth of gift disc: 1.5 m (maximum depth is 2.5 m). Signal frequency: 7 kHz audio frequency: 450 Hz working current:12 dcv "aa" (alkaline) 8x 1.5V power consumption: 0.6W weight: 3.2Kg (net weight), including packaging about 5.5Kg Model size: 1200CM (length) Working principle underground. The eddy current will produce a magnetic field, which will affect the original magnetic field and cause the detector to sing. The built-in high-frequency oscillator is composed of transistor VT 1 and high-frequency transformer T 1, which is a transformer feedback LC oscillator. The primary coil L 1 of T 1 and the capacitor C 1 form an LC parallel oscillation loop, and its oscillation frequency is about 220kHz, which is determined by the inductance of L 1 and the capacitance of C 1. The secondary coil L2 of T 1 is used as the feedback coil of the oscillator, and its "C" is connected to the base of the oscillator VT 1 and its "D" is connected to VD2. Because VD2 is in the forward conduction state, the "D" terminal can be regarded as the ground of the high-frequency signal. In the high-frequency transformer T 1, if the "A" terminal and the "D" terminal are the first terminals in the winding direction of the primary and secondary coils respectively, the feedback signal input from the "C" terminal to the base of the oscillator VT 1 can make the circuit form positive feedback and generate self-excited high-frequency oscillation. The magnitude of oscillator feedback voltage is related to the turns ratio of coils L 1 and L2. If the turns ratio is too small, it is difficult to start vibration because the feedback is too weak. If it is too large, the oscillation waveform will be distorted and the sensitivity of the metal detector will be greatly reduced. The bias circuit of oscillator VT 1 consists of R2 and diode VD2, where R2 is the current limiting resistance of VD2. Because the forward threshold voltage of the diode is constant (about 0.7V), it is applied to the base of VT 1 through the secondary winding L2 to obtain a stable bias voltage. Obviously, this voltage stabilizing bias circuit can greatly enhance the stability of VT 1 high frequency oscillator. In order to further improve the reliability and sensitivity of the metal detector, the high-frequency oscillator is powered by a voltage stabilizing circuit, which consists of a voltage stabilizing diode VD 1, a current limiting resistor R6 and a decoupling capacitor C5. Two potentiometers are connected in series between the emitter of oscillator VT 1 and the ground, which has the negative feedback effect of emitter current. The larger the resistance value, the stronger the negative feedback effect, the lower the amplification ability of VT 1, and even make the circuit stop vibrating. RP 1 is a coarse potentiometer for oscillator gain, and RP2 is a fine potentiometer. Debugging operation of assembling metal detector Assembly of metal detector is very simple and does not require any special tools. Just follow these steps: 1. Turn the lock on the metal bar clockwise to release it. 2. Standing with a detector in hand. When the distance between the probe disk and the ground is between 0.5 and 2 inches, let your arm rest naturally and comfortably. You can adjust the length of the probe rod accordingly. 3. Turn the lock counterclockwise to lock it in a fixed position. 4. Unscrew the nut on the detection board and remove it from the screw. Insert the metal edge, align it with the bracket hole on the probe board, reinsert the screw into the hole, and then tighten the nut. 5. Wrap the probe cable around the metal rod. Leave enough length for high-speed detection of uneven ground. 6. Insert the probe tray into the socket on the console. Be careful to ensure that the core wire on the plug is aligned with the socket. Note: the probe plug can only be inserted into the socket in one way. Don't insert it forcibly to avoid damage. Disconnect the probe tray cable from the probe tray. Please grab the plug and unplug it. Don't unplug the cable. 7. Loosen the nut on the probe disc and adjust the probe disc to the required angle (the probe disc should be parallel to the ground). Screw the nut to an appropriate degree to facilitate the detection of the rotation and vibration of the disc. Note: Don't screw the probe disk too tightly, and don't screw it with pliers and other tools. To install the battery, eight 1.5V batteries are needed as the power supply of the metal detector. Please note that only new batteries of the specified size and recommended model should be used. Do not mix old batteries with new batteries and batteries of different models (standard batteries, alkaline batteries or rechargeable batteries) or rechargeable batteries of different capacities. 1. Please turn off the instrument when charging the battery. 2. Press and hold the battery cover on the right and move the battery cover in the direction of the arrow. 3. Put 4 1.5V batteries into the battery compartment, and pay attention to the marks on the positive and negative electrodes. 4. Replace the right battery cover. 5. Press the left battery cover and move the battery cover in the direction of the arrow. 6. Put four 1.5V batteries into the battery compartment according to the correct direction of positive and negative poles. 7. Replace the left battery. The battery will leak chemical substances, thus damaging electronic components ● If there is no plan to use the detector for a week or more, please take out the battery ● Properly dispose of the old battery (1). After the battery is turned on, if the detection indicator light is dim or not bright, the detector will not be turned on, the volume is weak, the adjustment is not good, the operation is unstable, or there is deviation, indicating that the battery is insufficient in energy and needs to be replaced. (2) Turn the liquid level gauge off, and aim the pointer at 0 point on the scale with a screwdriver. With headphones, you can connect an earphone (not equipped, provided by yourself) to the detector, so that you can hear the sound alone. Using headphones can save battery, and it is easier to determine the subtle changes of sound, thus achieving better detection results. When using headphones, do not use the built-in speaker. Description of each operation key of the instrument: 1. The zero button has a button at the index finger of the probe handle, which is called the zero button. Press it and the pointer of the electric meter will return to zero scale. The zero button has a memory function, which can remember the working environment of the instrument at that time. For example, if the probe disk is placed above the soil, the soil will produce a certain signal to the instrument, which will make the pointer deviate to the zero scale. Press the button, the pointer will return to the 0 scale, and the signal of the soil will be gone, which can be used to detect metals. Therefore, it must be pointed out that the button cannot be pressed around the metal object, because after being pressed, the signal of the metal will be memorized, and the metal will no longer be detected. It must also be pointed out that when adjusting any knob of the instrument, you must first press the zero button, and then release it after adjustment. In the detection process, with the change of environment, the pointer of the instrument will deviate from the zero scale, and once the button is pressed, the pointer will return to the zero scale. Therefore, you should press this button all the time during the inspection. Note: it takes about one minute to warm up the machine just after it is started, otherwise press the down zero key, and once it is released, the pointer will deviate again and remain normal after preheating. 2. Tune button: Adjust the tuner button. The sound of musical instruments can be from scratch, from light to loud. When the sound starts from zero and is almost inaudible, it is called critical sound. The instrument has the highest sensitivity only when it is set to critical sound. Otherwise, no sound, too loud or no sound at all will reduce the detection effect. Note: When adjusting the critical tone, press the zero key, and then release it after adjustment. In the process of using the instrument, if the critical sound gradually becomes louder or smaller and disappears, press the zero key to recover. 3. Sensitivity The sensitivity knob controls the sensitivity of the detector. Turn the knob counterclockwise to the end, and the instrument has the lowest sensitivity. On the contrary, turning clockwise to the end has the highest sensitivity and the greatest detection depth. The adjustment of sensitivity depends on environmental theory, and the higher the sensitivity, the better. For example, the "mineralization reaction" is high, the sensitivity will cause false signals, and the instrument will ring everywhere, but nothing can be detected. At this time, the sensitivity should be reduced to support the influence of complex strata on the instrument. Note: Before adjusting this button, press down the zero button first, and then release it after adjustment. 4. The detection method of ground balance ground balance knob should first put the operation mode switch in the ground balance gear, and then adjust the ground balance button. Turn the ground balance button to the maximum, and the sound of the instrument will be enhanced. When placed in MIN, the sound will weaken. 5. Identification knob (identification) The identification knob is used to identify the working mode, so before turning this knob, turn the working mode switch to the identification gear. By aiming the identification knob at different scales, we can select different signals. If the identified target is an iron plate, the following phenomena will occur: when the probe moves close to its edge, the response is the same as that of ferrous metal, and after the probe is placed above the iron plate, the response is the same as that of non-ferrous metal. In this case, you can not only judge that the underground is an iron plate, but also estimate its area. Another function of the identification knob is to exclude small pieces of metal from similar metals and select large pieces of metal, such as burying a nickel underground. We turn the identification knob clockwise to the right (be careful to press the knob), and then move the probe over the coin. After several adjustments, the probe just makes a faint sound when it approaches the coin, which is the detection point of the coin. After setting this point, all non-ferrous metals with a volume greater than 5 points can make sounds, and non-ferrous metals with a volume less than 5 points are excluded because there is no signal. Note: Press the identification button before each adjustment and release it after adjustment. 6. Operation mode switch (ground balance &; The operation mode switch has two gears, one is ground balance and the other is identification. In the ground balancing gear instrument, all metals will make noise and have no recognition function. But the influence of formation "mineralization reaction" can be ruled out. After the instrument is well balanced, it has sufficient penetration, stable operation and accurate indication, so this method is generally used when starting to detect a certain area. Identification method and land balance method are used together. After the existence of metals is proved by land balance method, where there are a lot of scrap metal impurities, the identification files are used to distinguish the types of metals or select large and valuable metals. Except for the sensitivity adjustment potentiometer, the metal detector circuit has no adjustment parts. As long as the welding is correct, the circuit can work normally. When the whole machine is stationary, that is, when the speaker is silent, the total current is about 10mA, and when the sound is detected from the metal speaker, the current of the whole machine rises to 20mA. A new multi-layer battery can work for 20 to 30 hours. If the newly welded metal detector can't work normally, first check whether the components and wiring on the circuit board are welded incorrectly, and then measure whether the battery voltage and power supply circuit are normal. The voltage of zener diode VD 1 is between 5.5 and 6.5v, and the polarity of VD2 should not be reversed. Don't weld the primary and the head and tail ends of the oscillating coil in the detection disk by mistake. Before using the metal detector, it is necessary to adjust the length of the probe rod. Just unscrew the hose, push and pull the hose to a suitable length, then rotate the hose to wind the cable tightly and make the tip of the handle face upwards, and finally tighten the hose to lock it. In this way, when holding the probe handle, the thumb is just next to the sensitivity adjustment potentiometer. When adjusting the sensitivity of the metal detector, the detection disk (oscillating coil) should be far away from the metal, including the paper with aluminum foil. Then, turn the knob of the fine-tuning potentiometer to turn on the power switch and turn it to the half position. Then, adjust the knob of the coarse potentiometer to stop the audio sound of the speaker. Finally, fine-tune the potentiometer to stop the sound of the speaker. At this time, the sensitivity of metal detector is the highest. When a metal detector is used to detect metal, as long as the detection disc is close to any metal, the speaker will make a sound, and the sound will automatically stop when it is far away from a certain position. This metal detector is highly sensitive. When it is used to detect a large piece of metal, when the detection disk is 20 cm away from the metal object, as small as a paper clip or even a pin, the speaker will make a sound, but the coil of the detection disk must be close to the small metal object. Because the metal detector uses electromagnetic induction of oscillating coil to detect metal objects, it can detect covered metal objects through non-metallic objects, such as paper, wood, plastic, masonry, soil and even water layer, so it is very practical, for example, when decorating houses, it can be used to detect wires or steel bars in walls to avoid construction dangers and security risks; Another example is the metal detector for security inspection, which is made according to this principle. Precautions indoor testing and Precautions (1) Take away the watches, rings and other jewelry you carry with you, and then put the detector on a wooden or plastic table. (2) Adjust the angle of the probe disk so that its disk surface is parallel to the ceiling. Warning: Do not test the detector on the floor of the building. Because most buildings have metal in the floor, it will interfere with the measured object or completely confuse the signal. (3) Move the sample of the material to be tested (such as gold ring or coin) to a distance of about 5 cm from the probe disk. Note: the probe disk can't detect static objects, because you don't need a probe to search and scan at this time, so you must move the measured objects. If it can be tested with coins, it will be easier to test and use it outdoors if the plane (rather than the edge) holding the coins is parallel to the detection board. (1) Look for outdoor metal-free areas. (2) Put the sample you want to test (such as a gold ring or coin) on the ground. (If precious metals such as gold are used for testing, mark the placement area to facilitate future search. Don't put samples on tall plants or trees. (3) Hold the detector, make the detector disc parallel to the ground for 2.5-5cm, and slowly move the detector disc above the sample placement area for edge-to-edge (left and right) search.