Metal detection apparatus with a test device and test device

A test device for a metal detector for detecting contaminants in a product stream conveyed by a conveyor or gravity, said test device comprising:

• a first reel unit arranged at an input aperture of the metal detector and comprising a first reel drive unit that rotatably holds a first reel;
• a second reel unit arranged at an output aperture of the metal detector and comprising a second reel drive unit that rotatably holds a second reel, wherein at least said output aperture delimits a transfer channel of the metal detector along which products are movable through a coil system of the metal detector and that defines a detection zone that comprises a transmitter coil and a first and a second receiver coil dimensioned such that a current applied to the transmitter coil is configured to induce a first receiver coil signal in the first receiver coil and a second receiver coil signal in the second receiver coil that do not compensate one another when a metal contaminant is present in the detection zone;
• and
• an elongated windable sample carrier that extends through the detection zone, has a first end which is windably held by the first reel, a second end which is windably held by the second reel, and holds the at least one test sample;
• wherein either:
• the first reel drive unit or the second reel drive unit is controllable by the control unit to transfer the at least one test sample during the test intervals through the detection zone;
• or
• the first reel drive unit and the second reel drive unit are controllable by the control unit to transfer the at least one test sample during the test intervals through the detection zone.

A test device for a metal detector for detecting contaminants in a product stream conveyed by a conveyor or gravity, said test device comprising:

• reel units, each arranged at one of an input aperture and an output aperture of the metal detector, each comprising a reel drive unit that rotatably holds a reel, wherein said input aperture and output aperture delimit, at least in part, a transfer channel of the metal detector along which products are movable through a coil system of the metal detector that defines a detection zone, said coil system comprising a transmitter coil and receiver coils dimensioned such that a current applied to the transmitter coil is configured to induce a receiver coil signal in each of the receiver coils, respectively, that do not compensate one another when a metal contaminant is present in the detection zone;
• and
• an elongated windable sample carrier holding the at least one test sample and extending through the detection zone, said elongated windable sample carrier having a first end windably held by the first reel and a second end windably held by the second reel;
• wherein either or both of the reel drive units are controllable by the control unit to transfer the at least one test sample through the detection zone during the test intervals.