EGE-Elektronik Spezial-Sensoren GmbH - Special-Sensors for Automation

Metal detectors - Technology and application

The metal detector System 3000 is designed to detect medium size and larger pieces of metal. The system has a very effective means of adjusting sensitivity. When used with the MU 3300 amplifier, it will respond at the highest level of sensitivity to medium size parts like nails, washers, or pieces of flatware. When used with the MDV amplifier, it will respond only to larger pieces of metal like teeth from an excavator bucket, tools, or metal paneling. If not discovered, these items could destroy stone-crushing machines, vibratory equipment, or wood-chipping machines. When used in this manner, the metal detector is suitable for protecting machinery, whereby smaller parts will not interrupt operation of the equipment. It detects metal during bulk material transport by means of contactless measurement.

The System 3000 consists of an amplifier and an inductive detector  coil.  The  amplifier  is  equipped  with  an  automatic adjustment  regulator  that  ensures  reliable  operation  even when disturbing metal parts are in close proximity to the detector coil. In addition, the adjustment regulator also ensures that only metal parts that are in motion will be detected.

Metal detector EGE

One of the amplifier's tasks is to process the signals emitted by the metal detector coil and convert them into an electronic pulse. The detector coil generates an electromagnetic field. As soon as a piece of metal passes by the coil, it disturbs that field, resulting in a signal that can be evaluated.

The operator adjusts the metal detector's sensitivity on the potentiometer. The coil's sensitivity is dependent on several factors, including: the coil's environment, the electromagnetic characteristics of the material to be detected, and the speed with which the material is transported.

The MU 3300 amplifier has a self-monitoring function. Any error that appears in the system will activate a separate output relay. The unit's electronics are installed in a robust metal housing that has a window for the functional display.

The MDV 3172  and MDV 3220 amplifiers are particularly well suited for use in extremely difficult environments like those that involve dirt, temperature fluctuations, or vibration. These models therefore possesses only the most critical adjustment and display functions.

EGE metal detector

The detector coils are mounted with PVC columns on an aluminium baseplate that shields the coils from electromagnetic disturbances coming from the substructure. The baseplate simultaneously provides stability. Whenever the operator must arrange the detector coil in the presence of ironstructural elements, he can use the aluminium plate to shield the coil.

It is preferable to arrange the detector coils underneath the material transport belts in order to minimize the chance of mechanical damage to the coil. The distance to the belt's transport rollers should be at least equal to the width of a coil. In order to most effectively exploit the metal detector's sensitivity,  maintain  a  metal-free  area  around  the  detector  coil approximately equal to 1.5 to 2 times the coil diameter.

Metal detecor conveyor belt

If the coil is installed in a hanging position above the transport belt, always make sure that no structural parts made of iron are too close to the coil and especially that they do not vibrate. If this cannot be avoided, it will be necessary to reduce the sensitivity.  This  will  consequently  reduce  the  detection distance or may have the result that only large pieces of metal will be detected.
The detector coils have a special 3-meter long cable. If the distance between the detector coil and the amplifier is longer  than 3 meters, connect these two units with the KS 030 DS... extension  cable.  The  longest  permissible  distance  is  50 meters. In order to ensure that the system will work properly at that distance, we recommend using the EGE special extension cable.

By using connection box MA 125 two detector coils can operate together with one amplifier MDV.../ MU....The maximum cable length between one coil and the connection box MA 125 is 3 m.

Approval for safety applications
Sensors for personal security must have a qualifification approval according to EN 954-1 and must be labeled accordingly. Sensors that are not labeled must not be used for applications of this kind.

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