Safety Distance For Light Curtains

Guidelines for Safety Distance Calculations When Using Light Curtain Blanking Functions
The following is Wintriss Controls and Production Resources recommendations for establishing safety distancewith
the use of blanking functions:
Three types of blanking systems exist and vary depending on the Shadow light curtain model. Shadow II, IV, V, and
VI systems allow individual channel blanking bythe use of master and slave blanking windows. Shadow V, VI, VII,
and Shadow 8 systems support floating blanking functions and Shadow VII, and Shadow 8 support programmable
blanking.
When you add ablanking window or enable channel blanking functions you are effectively changing the MOS
(minimum object sensitivity) of the light curtain. MOS defines the smallest object that can always bedetected
anywhere in the sensing field. MOS in turn determines a light curtains Dpf (depth of penetration factor). Dpf is the
distance you can potentially reach into the light curtain field before beingdetected. For Shadow systems the MOS is
1.18” without the use of blanking. For a Shadow without blanking this equates to 3.1”. Dpf is added to safety
distance at the end of the ANSI safety distanceformula as follows:
Ds = K (Ts+Tc+Tr+Tspm) + Dpf
There is a formula for determining Dpf when MOS is known
Dpf = 3.4 (MOS-.275)
For Shadow
Dpf = 3.4 (1.18-.275)
Dpf = 3.1”
Each blanking window orthe use of a floating window increases minimum object sensitivity by .87”. The floating
blanking function on Shadow systems increases the object sensitivity by .87” anywhere in the sensing field.Example application:
1 blanking window is required
Hand speed constant (K) is 63 in/sec
Press stop time (Ts) is 170msec
Control response time (Tc) is 15msec
(note: Wintriss clutch/brake controlsinclude response time in the stop time measurement display)
Light curtain response time (Tr) is 30msec
Additional time allowed by the stopping performance monitor (brake monitor) (Tspm) is 40msec...