Machine Design

Inspection sensor uses contrast, brightness, and patterns

Though it looks somewhat like a Christmas ornament, the Checker 200 Series inspection sensor from Cognex Corp., Natick, Mass. (, is a high-tech vision system that inspects up to 6,000 ppm while providing reliable, precisely timed pass/fail results.

The disc of red, green, and cyan LEDs gives the device built-in lighting and enhances contrast, letting it clearly detect features other sensors might miss.

The Checker detects features on parts, not just edges. It also tracks parts in various positions on a moving production line, so parts need not be precisely aligned. And it doesn't need a secondary sensor to determine if a part is present. The device uses its brightness sensor to find light and dark areas. The contrast sensor finds features that contain light and dark, such as date codes, threads, and barcodes.

After some training, the pattern sensor knows what features look like and can be programmed to alert users when it spots one. There's also no limit to the number of features a single Checker can look for. It comes with software and USB connections. Checker 201 is for finding and inspecting parts, while the Checker 202 also includes ladder logic for custom setups. They operate in temperatures from 32 to 122˚F, withstand up to 80 gs of shock for 5 msec on each axis, and up to 10 gs of vibration at 10 to 500 Hz.

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