Proximity Sensors
July 2001
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Cherry Electrical Products’ GMR Series of magnetic proximity sensors, based on the giant magnetoresistive (GMR) principle, is said to represent a totally new approach to proximity sensing. The sensors are said to be highly sensitive and suitable for rugged applications in harsh environments or high-temperature applications such as industrial equipment. The highly sensitive sensors yield a large air-gap between the sensor and the magnet. Unlike Hall-effect sensors, the GMR is said to utilize an omnipolar sensing element, allowing it to be activated by either the North or South pole of the magnet. The sensors also deliver extremely stable operating characteristics over a wide range of temperatures, according to the supplier.

The GMR sensor package includes both the sensor and the signal-processing electronics. No further electronics are needed to process the digital output signal. Supplied with an open collector output, the sensor is reportedly capable of sinking 24 mA and is able to drive signals over wire lengths of up to 50 ft (15 m). The sensors also include industrial-grade protection circuitry for enhanced immunity against electrostatic discharge, electrical transients, radiated electrical fields, conducted energy, magnetic field energy, and reverse polarity power supply voltage to -24 V d.c.

The first sensor in the series to be offered is the Model MP100106. Packaged in a stainless-steel threaded barrel housing, the sensor includes 1 m (3.2 ft)of 22 AWG polyolefin cable. Operating voltage is 5-24 V d.c. at a maximum supply current of 10 mA. Operating temperature range is -40 to 125°C (-40 to 257°F) with a maximum operating point of 25 gauss.

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