12
Detection capability
(Resolution)
Height
Detection zone
Operating range
Fig. 3 Detection Zone
If the light curtain is retroreflective, the operating range is the distance between the active and the passive element.
Light curtains can have a “dead zone”, in which they are not able to detect the object due to the absence of beams.
When it is required that the dimension of the light curtain corresponds exactly to the height of its detection zone, the
light curtain is said to have
zero dead zone
.
SELECTION GUIDE
3. Detection Capability (or Resolution)
4. Detection zone
The detection capability of a light curtain is the diameter of the smaller object that will activate the device when it’s
placed in any point of the detection zone.
The value of the detection capability, together with response time, is crucial to calculating the minimum safety distance
required between the light curtain and the dangerous zone.
For single light beam sensors and for multiple light beams sensors (2, 3 or 4 beams), in place of detection capability,
it’s common to use the number of light beams. In this case, their purpose is to provide “body protection”, detecting the
passage of the entire body of a person.
For an introduction to the minimum safety distance calculation rules (described in EN 13855) see page 94 and the light
curtain’s technical documentation.
The detection zone is the area where any object whose dimensions are at least equal to the detection capability
activates the light curtain.
It is defined by its
height
and by the distance between the emitter and the receiver element (
“operating range
”).
Dead zone
