The downhome American adage, "If it ain't broke, don't fix it," seems like it must date back to colonial times. In fact, the phrase was popularized in the 1970s, but its widespread use makes it seem older than it really is. In that sense, the phrase is a bit like safety mats.

Introduced in the 1950s, safety mats became such a common tool in industrial machine guarding that some people seem to believe they date to the Industrial Revolution. Not quite.

A recent spate of articles is touting the death knell of safety mats in the wake of safety laser scanners. However, both machine guarding technologies have their place in today's industrial landscape. Decision-makers need a good understanding of the basic factors about each to make proper decisions regarding the type of guarding to employ for safety.

How Mats and Scanners Work

Safety mats are easy to understand. Typically, a safety mat is a simple, normally open switch that closes when weight is applied to it. Each safety mat has four wires that, when wired to a controller, provide the redundancy required to monitor the wires for opens and shorts due to mis-wiring or possible damage. Good safety mats feature heavy-duty, impact-resistant construction, with molded traction patterns to help prevent personnel from slipping.

Safety laser scanners use time-of-flight technology for distance detection. A pulsed laser beam emitted from the scanner is reflected back if it meets an object within the predefined areas. The reflected signal is registered by the scanner's receiver, which uses the time between sending and receiving the signal to calculate the distance between the scanner and the object.