Aka Sorex 7281 version 104 User Manual
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Selective Metal Detector «Sorex» 7281. Operating manual AKA LLC+7(495)623-4026 621-0481 http://aka.2000.ru [email protected] 21 Warning! The digit of the detected frequency of your search coil may depend on the particular search coil the device is tuning to automatically and software version. For search coils of any frequency range it may vary within ± 5%. After that your device automatically enters the ground balancing mode. Perform balancing in the clear area, similar to the procedure described in the Ground Balancing section, or, if there is no clear area, use a substitute (soil clump, red brick, ferrite). See the appropriate section on Ground Balancing. Press to exit from the balancing mode Your device is ready for operation with a new search coil. Warning! All aforementioned procedures are also necessary for software update (firmware update). If your device is equipped with several interchangeable search coils, we recommend you, in case of idle periods (for instance, seasonal stop-over), to reset the detector before starting the search, i.e. to adapt the electronic module to the search coil in order to avoid confusion. It should be mentioned here that the device has a built-in diagnostic system for the search coil excitation circuit. In case of circuit discontinuity and disconnected converter the device onscreen message says SEARCHCOIL ADAPTATION ERROR («АДАПТАЦИЯ ДАТЧИКА НЕВОЗМОЖНА») with the appropriate icon in the right part of the screen showing the DD search coil. Visual Identification Tool - Hodograph In the hodographic image mode target information is shown as a vector on the graph with axis Х and Y. Its size, form and angle depend on the electric parameters of objects such as conductivity, magnetic penetration, depth, geometry etc. It is almost impossible to describe all nuances, understanding comes with step- by-step progress in visual image memorizing and it depends on practical experience. But there are some consistent patterns which may help you to start the capture, such as: 1. Hodographs of small and medium objects made of iron are located in the left half of the screen. In other words, they deflect to the left from the centre of the horizontal axis along the bottom border of the screen. 2. Hodographs of nonferrous metal objects in most cases are located in the right half of the screen. In other words, they deflect to the right from the centre of the horizontal axis along the bottom border of the screen. Rarely, small low- conductivity metal objects as well as nonferrous objects masked by iron objects may give hodograph in the left half of the screen, but with a great deflection from the zero. (to – 35 VDI). Hodographs of large iron objects (helmet, axe, tin plate) also appear in the right half of the screen. N ail Grenade F 1- F oilTinc anC oinmm15 Ø C oinmm25 Ø D rain hat c h
Selective Metal Detector «Sorex» 7281. Operating manual AKA LLC+7(495)623-4026 621-0481 http://aka.2000.ru [email protected] 22 3. Larger reflection surface and higher conductivity of the object give stronger hodograph inclination to the right. For instance, with equal diameter and thickness, copper coin hodograph would be closer to the horizontal axis than the bronze coin hodograph. That happens because copper conductivity is higher than bronze alloy conductivity. 4. Hodographs of medium and large iron objects of non-round shape often have a form of wide loop, located both in the left and in the right half of the screen simultaneously. Hodographs of nails, arrow heads and other small iron objects have a shape of straight vectors in the left half of the screen. 5. Hodographs of nonferrous metal objects in most cases have straight shape or a narrow loop shape in the right half of the screen. The advantage of hodographic indication over VDI Two representative target hodographs are shown on pictures. These objects (a coin and a piece of rusty tin) give a nonferrous signal on all similar devices. In both cases target VDI would be +57 +58. It is seen in hodograph shape only that in first case (left picture) the target is sure to be nonferrous. In second case (right picture) it is safe to say that there is a flat iron target under the coil, a piece of iron roof coating, fragment of a kettle, for example. Multifrequency You are likely to be amazed by the fact that most devices produced worldwide have similar sensitivity, for example, to a brass disc with the diameter 25 mm and a fifty mm copper disc, although the second target is much bigger. It is known that small targets (coins) are better found in high search coil excitation frequencies. The point is that due to specific physical laws, each target group has its own optimum frequency which gives maximum sensitivity to those targets. To provide device performance in the search for large and small targets many manufacturers produce 2, 3 or 4 frequency detectors. Sorex 7281 is worlds first multifrequency device which allows working with search coils of any excitation frequency within the range of 2-20 kHz, putting into action the principle of the sensitivity acceptable for almost any group of targets. Standard Sorex 7281 set may include the following search coils: 15DD – 3 kHz, 9,5х12,5DD – 7(3, 14) kHz, 10DD – 7 kHz, 6х10DD – 7(14) kHz. Are there any practical recommendations on the selection of converter with a certain operating frequency? 3 kHz may be successfully applied in trashy areas to search for large targets made of ferrous and nonferrous metals as well as spoils of war.
Selective Metal Detector «Sorex» 7281. Operating manual AKA LLC+7(495)623-4026 621-0481 http://aka.2000.ru [email protected] 23 7 kHz – medium universal frequency for a wide range of goals. It can be used for the search for medium, small coins and spoils of war. This frequency is suitable for the on-the-ground reconnaissance. 14 kHz is a frequency suitable for small and medium coins, especially when they are lay on the ridge. This frequency is efficient for the beach search. Search and identification methods Sweep search coil above the surface keeping constant distance of 2-3 cm. This distance is optimum in terms of neutralizing soil mineralization, hence optimum for the right identification of the metal object type. Warning! An important thing to remember. Moving the search coil to the ground surface (not to the grass, but to the soil in particular) closer than 2-3 cm you get into the so-called Close Zone (CZ) of the search coil interaction with the low-magnetic and low-conductivity environment - the soil, as it was mentioned in the Ground Balancing section. In this zone the physical interaction pattern changes significantly, and that may lead to false responses of sound indication with high sensitivity levels. Avoid touching the ground with the search coil. Its important to keep constant distance between search coil and ground surface. Have in mind that proper object identification, number of false responses and sound indications of high sensitivity levels depend on the performance of this operation. Try to avoid horizontal search coil jerks. Optimum scanning speed 40-50 cm/s. Each successive scan must overlap the previous one at least by a half. Make additional scanning to detect object type above the center of the object, i.e. on the maximum signal line, keeping distance between the search coil and the ground if possible. For the same purpose it is necessary to scan found object in the direction with the least ground relief changes. In this case ground interference is barely noticeable. Device response single tones or tone sequences may go along with search coil interaction with metal objects. Pay attention to the following: If detector responds by single tone short signal with high pitch and signal level is pretty stable then there might be a small nonferrous metal object under the search coil at the 5 cm depth and deeper. If several (3 as a rule) high pitch signals are heard it means that same object is in the zone near the search coil (less than 5 cm). At the same time signal level on the display is pretty high, more than 50. Two low frequency short signals mean that there is a long ferromagnetic object (i.e. nail) located along the scanning direction. If such object is located across the scanning direction or perpendicular to search coil plane, then the device gives single low frequency short tone. It’s important to mention that DD-search coil has a complicated interaction
Selective Metal Detector «Sorex» 7281. Operating manual AKA LLC+7(495)623-4026 621-0481 http://aka.2000.ru [email protected] 24 pattern with metal objects in close zone (signal levels more than 80). That is why try to choose scan gap (distance) to provide 20 - 50 of signal level while identifying object type. In other words, try to indentify objects beyond close range zone if conditions allow you to do so. The so-called hot rocks cause problems during search operations ,their VDI is more than +84. To distinguish hot rocks and relatively large flat nonferrous objects (for example, five kopeks of Catherine II) VDI within +78 ...+86, device has special high-tone signal that differs from the usual signal tone for the nonferrous metal object. Hot rocks signal can be excluded using discriminator and setting value of first border to +86. However the most effective hot rock neutralizer is not a discrimination HRN (hot rocks neutralization) algorithm. With discrimination exclusion of sound response to hot rocks, due to ground influence, the aforementioned valuable objects with interference vectors close to hot rocks can be missed. This disadvantage is eliminated by the NHR-algorithm. Identification of flat iron objects. Such objects include steel beer caps, pieces of roof layers, pieces of cast iron and so on. These are the objects causing most identification difficulties and they are often mistaken for nonferrous objects, such as coins. Nevertheless, there is a range of technical tricks allowing distinguishing such objects. If such target gives a strong response (rating 10 and higher), the search coil edge scanning technique may be applied. With this scanning technique the aforementioned targets would give low tone of sound indication, and the display would show specific shift of the hodographic picture to the left (to the iron sector). These targets may also be scanned by a search coil located at the angle of 45° to the ground surface. It may not lead to the low-tone sound indication, but, at the same time, the hodographic picture will be more loop-like with a left-shift tendency (to the iron sector). As a rule, such output of both types of indication means that the object is made of iron. Search specifics in trashy areas. The search in these areas is the most complicated due to obvious reasons in terms of the application of a metal detector. It is impossible to give well-defined and concise “trashy” technique due to the variety and multiplicity of such models. However, some general guidelines listed below may significantly increase performance in such areas. Of course, the main M/M algorithm is used. 1. Select correct general sensitivity of the device (adequate to the area trash level). The higher the trash level is, the lower the general boost and identification channel sensitivity should be – ST. Use the “Economy” mode. Remember, high sensitivity does not always mean high search performance. 2. Try to move a coin in close proximity to the search coil. You’ll see that there is one target, but the unit gives three short tones. This comes from the fact that the actual interaction of the DD sensor with the target is complicated. What
Selective Metal Detector «Sorex» 7281. Operating manual AKA LLC+7(495)623-4026 621-0481 http://aka.2000.ru [email protected] 25 would happen, had there been several objects? It’s obvious that multiple targets located in the close zone are likely to tangle comprehension of the sound and visual information. This fact leads to the important practical conclusion. Do not search in trashy areas with a minimum gap between the search coil and the ground, especially those with the on-surface trash. Choose optimum scanning gaps. In this case they may amount more than 25% of the diameter of the search coil used. 3. Use short sweep technique (5-15 cm) to search for, identify and locate useful targets. 4. The right scanning direction for a group of targets may minimize influence of neighboring objects. Based on the above stated, the most important factor of the «trashy» area search performance shall be your field experience and practical skills. Additional menu Model 7281 has the additional menu extending sound indication capabilities and including ground balancing automatic tuning option. To enter additional menu press and hold . To browse menu entries press and . To select menu entry and enter the submenu press . To select the submenu parameter press and . To change the parameter selected in the submenu press and . To exit the submenu and enter the menu, to exit the menu and enter the search mode press . Menu entries: 1. Tone borders (Border 2, Border 3, Border 4); 2. Tone tuning (RT Frequency, LT Frequency, Frequency 2, Frequency 3, Frequency 4, Frequency 5); 3. Additional Parameters (Contrast, Startup melody). Tone borders. In this submenu you can change borders of VDI sound sectors according to your major search targets. Narrowing or widening them you can achieve sound recognition of the group of targets common to your search area. To exit the submenu press . Tone tuning In this submenu you can change tonality of identification signals comfortable for your ear. The bigger number is, the higher the tonality goes. The lowest tonality corresponds to the iron, the highest one corresponds to large high-conductivity metal objects. When you change the tonality we suggest you to consider that the tonality of the
Selective Metal Detector «Sorex» 7281. Operating manual AKA LLC+7(495)623-4026 621-0481 http://aka.2000.ru [email protected] 26 threshold tone has its own separate value. It is not recommended to assign this or close tonality to any group of targets, otherwise its identification signal will merge with the threshold tone signal and it would be indistinguishable against such background. Add. Parameters (additional parameters) Contrast This option allows adjusting display contrast to the level comfortable for you. Startup melody. This option allows selecting one of two startup melodies of your choice or turning off the startup melody at all. Troubleshooting In case of any malfunctions, first of all, reset your device to factory settings. Turn off the device, press M button on the panel and turn on the device, holding it till the startup screen appears. You will see a Factory Settings" (Заводские настройки) onscreen message. In most cases this reset will solve the problem. Phantom search signals when there is no metal targets are possible in following cases: 1. Incorrect ground balancing. With incorrect ground balancing, when the balance phase (a digit in the left corner of the screen) is shifted to the minus values too much, false responses are possible in the nonferrous metals sector when bumping the search coil over mounds and plants. Balance the device accurately or adjust ground phase value by 1-2 degrees in the manual balancing mode pressing +. If the balancing phase is shifted to the plus values too much, false responses are possible in the iron sector. Balance the device accurately or adjust ground phase value by 1-2 degrees in the manual balancing mode pressing -. 2. Weakened contact in the slot of the coil jack in the module. Put the device into horizontal position and tap the unit cable with your finger. If the device responds with sound signals, the problem is in the slot. Slightly force apart pin sections of the unit (approximately 1 mm) and screw the nut tightly. If it did not help, your device is likely to have a defective search coil jack soldering, or the jack is damaged and repair is necessary. 3. If a light finger tapping on a coil (see section Search coil Replacement) connected to a balanced device such device gives short tone signals, then the search coil is defective and subject to repair or replacement. The 15 DD search coil may give light phantom responses when bumping over the edges of the coil circle, it is a design feature of the large search coil.
Selective Metal Detector «Sorex» 7281. Operating manual AKA LLC+7(495)623-4026 621-0481 http://aka.2000.ru [email protected] 27 Warranty Manufacturer guarantees operational capability of the metal detector provided that the consumer follows operation conditions. Warranty period 24 months starting from the sale date. Manufacturing defects shall be repaired by the Manufacturer during the warranty period free of charge provided that there is no damages in electronic module and search coil. This Operating Manual with the sale date mark should be provided together with the device in case of warranty repair. Warranty period is calculated from the date of manufacture in case there is no sale date mark. Send claims to:
Selective Metal Detector «Sorex» 7281. Operating manual AKA LLC+7(495)623-4026 621-0481 http://aka.2000.ru [email protected] 28 QA/QC certificate Metal detector «SOREX» 7281, № __________________ Date of manufacture «____»________________20__. Manufacturers Stamp QA/QC Passed ____________________ Signature. Sale Date «____»________________20__.