The Arado 320 deep seeking analytical Metal Detector has been designed to achieve great depth and detection efficiency together with ease of use. Please read these instructions thoroughly several times over before attempting to use the detector.
Please be aware that, although an excellent find-rate may be achieved almost immediately, optimum results will only be achieved after a lengthy period of practice and experimentation, especially if your detecting experience up to now has been solely with motion detectors.
This analytical metal detector operates at the Very Low Frequency of 4.5KHz using the Transmit / Receive principle. It is able to detect objects in the ground much deeper than the old Model 120B and 130 detectors. Although operating in similar way to these earlier detectors, the 320 has a totally different circuit, method of set-up and tuning. It has been designed to achieve even greater depth on the small or medium-sized non-ferrous metal targets so successfully detectable with the 120B and 130 while at the same time maintaining the accuracy of discrimination between ferrous and non-ferrous. Most importantly, the 320 can also detect larger items or concentrations of small items (such as hoards of coins) at considerably greater depth.
The ARADO 320 consists of two detectors operating together in such a way as to both detect and identify instantly whether or not a target is ferrous. An all-metal ground exclusion circuit provides the audio output and because the effects of iron mineralised ground are reduced or eliminated, searching is made easy and the depth of detection is the maximised. As all metal objects located will produce a positive audio response from the detector, a ferrous/non-ferrous discriminating circuit provides a simultaneous visual indication on the meter of any magnetic disturbance in the ground. With careful use, it is possible with almost all targets to correctly identify whether they are ferrous or non-ferrous, thus minimising any unnecessary digging. Ground magnetism does affect the meter and experience has to be gained before the greatest accuracy in identifying targets can be achieved.
Before commencing an actual search it is advisable to get to know the controls and the kind of signals that the detector will give. The way to do this is firstly to lay your detector on a wooden table with the search coil well away from any metal. Use a selection of coins and other metal objects and after tuning the detector pass these items in turn across the bottom of the search coil and at varying distances. Observe the response of the headphones and meter to these items. Repeat the same tests using ferrous items such as nails or rusty iron.
It is strongly recommended that the above items are then buried at suitable depths in metal-free ground and the detector's in-ground response to them learned thoroughly before any serious searching.
THE ARADO 320 HIGH-PERFORMANCE ANALYTICAL DETECTOR
The Arado 320 is able to achieve great detection depth on small and medium-sized non-ferrous metal items at the same time as correctly identifying almost all such items as non-ferrous. It is only by correct identification that the operator can gain the total confidence and enthusiasm needed to dig deep targets.
Highly accurate analysis is possible because the magnetic properties of detected iron objects, even at maximum depth, can be observed on the meter. All targets not displaying any ferromagnetic properties can safely be assumed to be non-ferrous. (Only about 99.7% accuracy is achieved in practice because rings, loops and flat slabs of iron are occasionally encountered which are wrongly identified as non-ferrous.)
The basic mode of operation of this detector is similar to that of the Arado 130 and 120B detectors, but with a different means of removing ground effect which allows more effective performance on intensely magnetically mineralized ground. The G.E.B. control is a 10 turn potentiometer used to completely eliminate ground magnetism disturbance on the audio signal. The Audio Threshold control is a single turn (300 Degree) potentiometer. Desired audio threshold is set by rotating this control whilst holding the push-button depressed.
Never attempt to search without audio threshold signal or severe loss in sensitivity may occur.
Due to the extremely high performance and sensitivity of this instrument, substantial operator experience is essential for best results. Optimum results will be achieved only if the operator understands the detector and uses it correctly. It is particularly important to ensure that all ground effects are carefully eliminated (phased out) and that this state is maintained at all times.
The standard detector uses a 25 cm diameter search-coil and a substantial nickel-metal hydride rechargeable battery pack (9.6v 700mAH). A battery charger is provided, operating from 240 volts AC Mains (13 Amp plug). The charging time required is approximately one hour for every hour of use. It is not necessary to remove the batteries from the electronics module to charge them as the charger output plugs directly into the socket on the module. Do not attempt to fast-charge the battery.
Considerably more depth can be achieved with the 37cm diameter coil, but at the cost of greater operator fatigue. Although total recovery rate will often be lower, the average quality and value of coins and artifacts recovered tends to be better with the larger loop due to the greater age and better condition of the objects found.
SWITCHING ON AND SETTING UP THE ARADO 320
1. Switch on and set to Gain Level 2.
2. Depress handle-mounted push-button and while keeping button depressed, set loudness of threshold tone to that desired. (It is impossible to use machine efficiently with no threshold tone (i.e. completely quiet)release the push button. The audio threshold can now be re-set at any time by simply pushing and releasing the button.
3. Set G.E.B. (Ground Effect) control to give minimum possible ground disturbance by adjusting the G.E.B. control until minimum audio variation occurs when lowering search-head from about 20cm down to about 5cm above ground. (Similar to setting up White 5000 and 6000 in G.E.B. mode.) Ignore meter whilst doing this.
Re-tune while holding the coil in the air and then lower to the ground, if the audio goes loud turn the ground balance controle anti-clockwise one turn, if the audio goes quiet turn the ground balance control clockwise one turn.
Hold coil clear of the ground and re-tune. Repeat this until the audio does not change when the coil is lowered to the ground.
The ground balance in now set.
4. Repeat 2 or 3 times in locations at least 100cm apart to be certain the control has not been wrongly set due to metal items being within detection range.
The machine is now ready for use.
The meter needle will move from side to side as the coil is lifted up or down, this is normal and will be worse on highly mineralized ground.
The meter is referred to only after an audio signal is detected then the coil is moved to one side of the object, retuned and moved towards the signal at a constant height noting the reaction of the needle.
A movement left, or a small left movement before going right, indicates ferrous.
A movement only right or no movement indicated non ferrous.
This is the hardest thing to learn and only with practise will you be able to use the 320 to it's full potential, this is not a turn on and go machine.
Over extremely magnetic ground, it may be necessary to operate on Sensitivity 1 or 2, whereas on very good (non-magnetic) ground, optimum results may be obtained on Sensitivity 3 or even 4. Increasing experience will also allow more sensitivity to be used in any given location.