Pilz: a general cognitive error in the choice of light curtain resolution

Safety light curtain resolution quantification

Among the various safety light curtain products on the market, one of the most important selection parameters is the resolution. Resolution is usually quantified in millimeters (mm), such as the usual 14mm, 20mm, 30mm, etc. These quantified indicators represent the gap between the sensing functions of the safety light curtain sensor.

Intuitive classification or wrong perception?

Depending on the resolution, light curtains are often categorized into finger, hand and body protection types to characterize the most appropriate application scenario, but this intuitive classification is often misunderstood. Many designers believe that the type of light curtain can be directly selected according to the human body part that causes damage from the source of danger, but such speed matching method often does not meet the requirements of the standard.

Correct selection of safety light curtains

According to the European standard EN ISO 13855, the minimum distance of the safety light curtain from the hazard source, the resolution of the light curtain, the installation method, the stop response time of the system, etc. should be substituted into the formula and calculated. Vertical installation, horizontal installation and installation with a certain angle of inclination have different formulas. Only considering the resolution of the light curtain, the positioning method, the stop response time and the distance from the dangerous source are the correct methods to meet the standard.

For example, the light curtain selection of some devices has chosen the hand protection type according to the speed matching method. Once the light curtain is limited in location from the hazard source, or if the system's stop response time is too long, consideration should be given to increasing the resolution of the light curtain to meet the requirements of EN ISO 13855.