Rockwell Automation has launched a camera-based safety sensor system as a low-installation-cost alternative to light curtains or safety mats for guarding access to machinery via rectangular (or some irregular) apertures. The GuardMaster SC300 sensor is fixed to one corner of a machine frame and monitors patterns printed on a special reflective tape attached to the opposite sides of the frame. It senses if an object blocks the camera’s view of the patterns and has a 20ms response time.

The system, designed to detect hands or arms, offers a choice of resolutions: 24mm (for guarding openings from 0.4–1.2m) or 30mm (0.6–1.5m). It has a maximum operating range of 2.12m and can monitor machine openings up to 1.5 x 1.5m. A test rod is supplied with the installation kit to verify the sensing-field detection area after teaching the device.

Two of the sensors can be synchronised to monitor larger apertures (up to 1.5 x 3m). The openings do not have to be perfectly rectangular, as long as the camera can see the tape fixed to the far edges. An opening that extends over two adjacent sides of a machine can be monitored using two sensors.

The IP54-protected Type 3 device is aimed at SIL 2 / PL d applications. It costs just over £1,000 in the UK, making it comparable to the cost of a light curtain, but it is quicker and cheaper to install and maintain. No software is needed to set up the sensor. For higher-risk (SIL 3 / PL e) applications, a light curtain will still be needed.

A similar system, called the V300, is available from Sick.