Highly accurate pattern recognition sensors

Opto-Electronics

23 January 2008 Opto-Electronics

Murata has released four new products in its BS05 series of magnetic pattern recognition sensors. The BS05M1HFAL, BS05M1KFCA, BS05M1KFFA and BS05M1KFBB magneto-resistive sensors are designed for ATMs, banknote counters, detectors and other validation applications.

The devices are suitable for detection of magnetic thread or magnetic ink, and enable simple and quick mounting. They retain around 70% of their output voltage at a 0,1 mm gap between sensor and substrate, compared to just 4% for typical coil head sensors. Along with their stable frequency characteristic, which is independent of the scanning speed, this makes them suitable for high-speed processing devices that demand high accuracy.

Magneto-resistive sensors consist of a permanent magnet and two sensing elements to ensure compensation for changes in temperature. When a magnetic material is passed over the sensor, the elements detect a change in the magnetic flux density, which is converted into an electrical signal. In banknote validation applications, the sensor is typically mounted beneath a pressure roller which helps keep the banknote in contact with the sensor's surface. In Murata's multichannel devices, multiple sensors are mounted next to each other, to allow magnetic pattern recognition over the whole width of a banknote.

The BS05M1HFAL is an 8-channel sensor with channel width of 3 mm, while the BS05M1KFFA has 13 channels, each 10 mm wide. Both have all their channels mounted in a straight line. This layout is especially useful in banknote validators that use a pressure roller, as the centre of the roller can be directly above the line of sensing elements, leading to lower signal loss and eliminating time differences between signals. The in-line layout also eases handling and PCB assembly and reduces the size of the pressure roller and sensing assembly.

The BS05M1KFCA six-channel and BS05M1KFBB 13-channel sensors have 10 mm channel widths with channels offset in alternate directions to make a zigzag style configuration. This ensures there is no physical gap between each channel, leading to very reliable detection of banknotes. These sensors are therefore targeted at high end machines that have high scanning speed and require high detection reliability.

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Highly accurate pattern recognition sensors

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