How to Choose & Use Industrial Metal Detectors
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MD-70 Ask Orange > TM Provides solutionsto process problems How ToComplete guide toIndustrial Metal Detectors > World authority in advancedtechnology for magnetic, vibratoryand metal detection applications. size="-3">

HOW TO CHOOSE AND USE METAL DETECTORS PageINTRODUCTION 3LIMITATIONS 3 DEFINITIONS 4 THE STATE-OF-THE-ART 4 PRINCIPLES OF METAL DETECTORS 5 WHERE SHOULD METAL DETECTORS BE USED? 5 BASIC LAYOUT OF A METAL DETECTOR 6 METAL DETECTOR STYLES 11 SELECTING THE RIGHT METAL DETECTOR 18 GETTING THE MOST FROM YOUR METAL DETECTOR 20 SUMMARY 25 Ask Orange > TM is a collection of process solutioncase studies and how-to reference manualsdesigned to improve understanding and simplifyspecifying sophisticated magnetic, vibratory andmetal detection equipment needed in most process industries. Most of this...

When Eriez Magnetics first opened its doors in 1942, the focus was on providingmagnetic separation equipment-such as plate and grate magnets-to customers who wanted to remove tramp iron and steel from product flows. These magnetic devices, as well as others developed over the years, have proven effective at eliminating contamination by ferrous materials. However, many customers with ferrous contamination problems also experience contamination by non-ferrous metals, such as brass, aluminum, and stainless steel. To attack these problems, Eriez added a limited range of metal detectors to their...

DEFINITIONS For reference, here are some terms that will be used frequently in the followingdiscussion. COIL A loop of wire, usually only one or two windings, that is used as a transmit and/or receive antenna to detect metal. FILTER METAL-FREE ZONE SENSOR Sometimes referred to as signal processor. The electronic component of a metal detector that evaluates the voltage emitted by the sensor and determines if that voltage indicates that metal is present. Modern filters can determine the type and size of metal by evaluating the amplitude and phase of the sensor voltage. The region surrounding...

The state of the art is typified by solid state, microprocessor-controlled detectionequipment, generally incorporating sophisticated embedded signal processors, or networked to remote computers (or both). The state of the art metal detector has inherited all the reliability, ruggedness, accuracy and flexibility characteristic of modern electronics wedded to computer science. Such detectors can solve many formerly intractable problems, such as detection and rejection of very fine non-ferrous materials in free-falling products, interference from nearby moving metallic equipment, and...

Metal detectors can also be used is to verify that desired metal objects ARE present inpackaged products-such as novelties in breakfast food boxes. Here again, it is important to monitor the product both before and after the process step in which the metal item is to be inserted, to be certain that the detected metal at the output point is the desired object and does not include contamination carried from the input. BASIC LAYOUT OF A METAL DETECTOR An industrial metal detector consists of four main components as shown schematically inFigure 2: Briefly, the sensor is a device that will react...

DID YOU KNOW... Eriez offers a combination vibratory conveyor/metal detectorunit. These systems provide a high level of accuracy. 10 POWER SUPPLY ALARM Most metal detectors are sensitive to power supply variations, and special power supplies are commonly used. These supplies incorporate noise filters and quench arcӔ circuits to eliminate false tripping by the metal detector when it is switched on or off, or when another component in the system (conveyor drive motor, for example) is switched. The most common alarm is a flashing beacon, activated by the metal detector output relay. A siren,...

RECORD KEEPER The most sophisticated modern metal detectors keep records of all detections occurring in a previous time period. These are stored internally and may be accessed on demand by the operator or by remote command from networking software. An individual record will typically include details of the product being processed and the detector settings when the detection occurred, as well as the exact time and the characteristics (at least the magnitude) of the detection signal. The recorded detection time is critical to identification of possibly similarly contaminated product as well...

14 VERTICAL APERTURE STYLE The E-Z Tec and E-Z Tec DSP vertical aperture metal detectors use the same technology as the horizontal aperture style. An example is shown to the left. They are intended for use where the greatest achievable sensitiv- ity is required, and where the product to be inspected is in free fall or is being transported pneumatically. Although standard models exist, these detectors are almost always custom-designed for each application. Vertical aperture detectors are also generally supplied complete with a section of non-metallic, static-resistant ducting to contain the...

15 LIQUID LINE STYLE In some ways similar to the vertical aperture detectors, the sensor in the liquid line detector style surrounds a separate pipe which carries the product for inspection. However, unlike the vertical aperture detectors, the medium within the pipe is now liquid. The liquid may be carrying particulate product as aslurry, or may be the product itself. In either case,the pipe is generally under internal pressure, and frequently carries a hot product. It may be horizontal or vertical. Because of the liquid medium, static is not generally a problem. The internal pressure and...

WEBBING STYLE Webbing style detectors are optimized forexamination of sheet-formed product, such as paper, textiles, board, plastic, floor tile, etc. and are available in both single surface and aperture configurations. Because the contaminant is bydefinition presented to the detector in a very limited area, quite close to the detector coils, at least theoretically there need not be any great difference in sensitivity between the aperture and single surface detectors of this style. The aperture configuration may allow for more variation in web position without losing sensitivity, offset by...