Principle Of Operation - Allen-Bradley SafeZone Mini User Manual

Chapter 2 Product Description
18
Or, it must be possible to transfer the dangerous state of the machine, system,
or vehicle to a safe state at any time with the OSSDs on a safety controller
connected to the SafeZone Mini device.
• The SafeZone Mini device must be mounted and configured such that it
detects objects as they enter the hazardous area (see
page 39 and Commissioning on page
• The optical path of the safety laser scanner must always remain clear. Do
not cover the optical path with transparent objects such as protective
windows, Plexiglas, and lenses. To maintain the protective function of
the safety laser scanner do not bypass the contamination measurement
function by such measures.

Principle of Operation

The SafeZone Mini device is an optical sensor that scans its surroundings in
two dimensions with infrared laser beams. It is used to monitor hazardous areas
on machines or vehicles.
The SafeZone Mini device works on the principle of time-of-flight
measurement (Figure 1). It sends out short pulses of infrared light (send
pulses). Simultaneously, an "electronic stopwatch" is started. When the light
hits an object, it is reflected and the safety laser scanner receives it (receive
pulses). From the time between sending and reception (∆t), the SafeZone Mini
device calculates the distance to the object.
Figure 1 - Time-of-flight Measurement
SafeZone Mini
Send pulses
Receive pulses
In the SafeZone Mini device, there is also a mirror that rotates at constant
speed and deflects the light pulses such that they cover an arc of 270°
(Figure 2). In this way, an object can be detected in the protective field within
270°. The first beam of a scan starts at -45° relative to the back of the safety
laser scanner.
The SafeZone Mini device sends a pulse of light with an angular resolution of
0.5° (A). As a result resolutions between 30...70 mm (1.18...2.76 in.) can be
achieved (B).
Rockwell Automation Publication 442L-UM005B-EN-P - April 2017
Mounting on
71).
Send pulses
Receive pulses