What Is a Needle Detector?
A needle detector is a device designed to identify broken needles, staples, iron needles, nails, and other metal fragments in various textile and industrial products. It alerts the operator through a lamp and an electronic buzzer when a foreign object is detected. These detectors range from handheld types for portability to tabletop models for space efficiency, to conveyor types that enhance productivity in mass production settings.
Applications of Needle Detectors
Needle detectors are extensively used in fields such as apparel, food, recycling, medicine, medical, sewing, logistics, baby products, sporting goods, chemical, security, and crime prevention. Common applications include:
- Inspecting small textile products like ties and stockings
- Apparel inspection for forgotten needles
- Detecting metallic fragments in pharmaceutical products
- Medical use for hairpin removal
- Security and safety detection
- Detecting needles in sewing products
- Finding iron fragments in textiles, carpets, and felts
- Identifying metal objects in industrial materials like rubber and plastic
- Baggage and parcel inspection
- Detecting small metal pieces in various products
Principles of Needle Detectors
Needle detectors operate on the electromagnetic induction principle. A permanent magnet and a search coil in the sensor head generate magnetic lines of force. When a magnetic object like a needle distorts these lines, it induces an electric current. The search coil detects this current and triggers an alarm or stops the conveyor. While primarily sensitive to magnetic objects, these devices may also respond to dust, dirt, and non-magnetic metals. To enhance sensitivity, some models feature dual sensor heads or bi-angular detection. Modern needle detectors may include features like a large color LCD touch panel, inspection history data recording, printing capabilities, adjustable sensitivity levels, and conveyor speed control.