❱ ❱ Colour sensors are helping to measure creepage of bogie wheels on railway tracks in the laboratories of Huddersfield’s Institute of Railway Research


❱ ❱ The colorSENSOR CFO200 non-contact colour recognition sensor is available with a range of probes to suit different applications


creepage, which represents speed differences of around 0.1%.” Access to the ends of the bogie axle was restricted, so it was necessary to look for a non-contact sensor to take measurements of the wheel speed. The IRR initially considered using a magnetic (inductive) sensor but this was discounted due to the required tolerance between stationary and rotating parts and the high cost. “We then approached Micro-Epsilon, who we already had a


relationship with, for one of its non-contact colour recognition sensors, which we wanted to use as an optical encoder to count the pulses of the wheel as it rotates. Coupled with a split zebra disc, which can be clamped to the axle and thereby negating access to the axle ends, and a large stand-off between disc and sensor, this has proved to be a good method,” explains Woodhead. The CFO 200 is mounted at a distance of 10mm from the wheel as it rotates. The pulse count data is fed to other test software programs that allow the researchers to calculate the frequency of pulses, the rotational speed, the linear speed of the wheels and from this the creepage. “Although this is a fairly unusual application for a colour recognition sensor, we’ve been very pleased with the sensor’s performance during the research. We are also impressed with how easy it is to set up and integrate with our other software programs and test platforms,” Woodhead concludes.


❱ ❱ The non-contact colour sensor is used in conjunction with a Zebra encoder disc to calculate the rotational speed of the bogie wheelset by counting the pulses as the wheel rotates


CONVENTIONAL COLOUR SENSING


The colorSENSOR CFO200 colour recognition sensor is designed for high precision true colour measurement. The sensor stands out due to its high colour accuracy, good reproducibility, high measuring rate and modern communications interfaces for easier network integration. With a robust aluminium housing, the CFO200 operates in temperatures from -10°C to +55°C and is protected to IP65. Although the IRR wheel creepage application is an unusual one for this type of sensor, there are many use cases that represent more conventional applications for colour sensing. These include a wide range of industrial applications including colour sorting tasks in food and beverage processing, colour inspection of interior parts in the automotive industry and recognition of colour marks in the printing industry as well as quality control in packaging, cosmetics, medicine and plastic products. Equipped with optical fibres and focus lenses, the


sensor can also be used in tasks where space is restricted, as the sensor head requires minimal space. Gray-scale detection and high colour accuracy are combined with Ethernet and RS232 communications interfaces.


Climatic & Vibration Testing Vol 2 No. 2 /// 3


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