Colour discrimination sensor now offers analog output

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March 2001 Sensors & Transducers

Omron has introduced an analog output version of its E3MC RGB colour sensor. Able to accurately discriminate not just different colours but also shades of the same colour, the sensor provides three separate analog outputs (0-10 V) for the three primary colours of red, green and blue, from which the actual colour detected can be deduced. The sensor discriminates colour without being influenced by changes in ambient temperature, brightness or positioning of sensing objects.

The analog colour sensor is ideally suited to quality control tasks and manufacturing processes where colour is a crucial element. The analog output provides the control system with both verification that the detected colour is within tolerance, and with a realtime indication of potential problems as colour drifts towards the limits of tolerance and beyond. This gives users an effective tool for continuous process improvement and pre-emptive maintenance.

The E3MC detects colours by making use of the fact that the reflection ratio of a primary colour reflected by an object varies with the chromaticity of the object. By using a multilayer polarised filter, the E3MC emits red, green and blue light on a single optical axis. The RGB content of the received light is processed on board the sensor to determine the level of each output and thus discriminate the colour of the object. A monitor photodiode compensates for any LED output variation that might be caused by temperature change.

Options for the analogue E3MC RGB sensors include models with built-in amplifiers for long distance setting, and versions with fibre-optic heads for tiny spot sensing. The sensing distance for the built-in amplifier version is specified at 60 mm, and the device will tolerate a ±10 mm variation in the sensing surface, thus assuring stable detection. The fibre-optic variant with the standard head offers a 20 mm sensing distance with a ±4 mm threshold, although other fibre types are available with different spot diameters and sensing distances. All models are protected to IP66 for reliable operation in the most arduous of environments.

Yelland Control

(011) 874 7770

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Colour discrimination sensor now offers analog output

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