C) Interference - Renkforce MD 150 Operating Instructions Manual

• When a metal set on the DISCRIMINATION (7) dial as eliminated is found, the pointer on the indicator moves
anticlockwise into the left-hand section of the analogue display (5). A quieter audible signal is emitted, or no signal
at all. The metal type is audibly eliminated. If no metal has been eliminated, the analogue pointer moves in the right-
hand section of the analogue display (5) only. When a non-eliminated metal or an alloy has been differentiated, the
pointer moves anticlockwise into the right-hand half of the analogue display (5). An audible signal is emitted which,
depending on the proximity and size, is quieter or louder.
False signals
• A false signal is an indication of an alleged object, even though the object is not there. Move the detection probe (1)
several times over the position of the signal. If the signal is strong and repeats easily, it is most likely an object
hidden in the ground. In the event of irregular and inconsistent repeated signals, it is most likely a false signal.
• An oscillating signal is usually caused by external interference (e.g. fluorescent tubes, radios, electrical cables and
other metal detectors). This cannot be eliminated by adjusting the settings.
• Identifying false signals requires practice and experience.

c) Interference

False signals can occur for the following reasons:
• The sensitivity is too high.
• The metal detector was moved too quickly or at an incorrect angle.
The analogue display (5) indicated the wrong metal type.
• There are several different metallic objects.
• The object consists of an alloy that the metal detector cannot recognise.
• The metallic object is heavily oxidised.
• The sensitivity is too high.
• The more the pointer on the analogue display (5) moves, the larger the object (or the shallower the object for
smaller objects).
• The pointer on the analogue display (5) moves most strongly with highly conductive metals. If the pointer on the
analogue display (5) does not move significantly each time the detection probe is moved over the area that you
suspect may contain an object, this probably indicates that there is only scrap metal.
• The success/accuracy of the metal location depends on several factors. These include:
- The angle at which the object is inserted into the ground (detection plane)
- The depth of the object
- The object's degree of oxidation
- The size of the object
- Electromagnetic and electrical interference (e.g. underground cables) in the vicinity of the object
• Due to these factors, it is important that you familiarise yourself with the metal detector and how it responds before
attempting to search for objects.
32