ANSI B11.19-2003 calculation formula for the minimum safety distance for AOPD with right-angle approach (point of operation guarding):

The following calculation formula applies for applications of optoelectronic protective devices with approach direction of body parts in an angle of 30° to 90° to the protective field level (see page 38, fig. 4.2.1-4):

Ds = Hs x (Ts + Tc + Tr + Tbm) + Dpf

Ds The minimum safety distance in inches or millimeters between the next danger zone and detection point (protective field)
Hs Hand speed (approach speed of body parts or bodies) in inches/s or millimeters/s. ANSI B11.19‑2003 provides hand speeds of 63 100 inch/s. 63 inches/s is frequently calculated, which equals 1600 mm/s.


Elements of the entire stop time of the machine:

Ts Stopping time of the machine measured at the last control element in s
Tc Response time of the machine control system in s (note: Ts + Tc are usually measured with a stopping time measuring device)
Tr Response time of the protective device (incl. interface module) in s
Tbm Additional response time for the brake wear and tear which is not detected by the tracking monitoring of the brakes. If the machine does not have a brake monitoring unit, approx. 20% of the measured tracking time (Ts + Tc), or a factor in accordance with the specifications of the machine manufacturer must be added as a reference value for the brake wear and tear.
Dpf Penetration factor in inches or millimeters. This additionally added distance is based on the fact that, depending on the resolution of the protective device, a body part can get a certain distance closer to points of operation before it is detected by the protective device. Dpf (inches) = 3.4 x (resolution – 0.276), result > 0


Resolution Dpf (mm) Dpf (inches)
14 mm 24 0.9
20 mm 44 1.7
30 mm 78 3.1