27
OS32C
User’s Manual
Chapter2
Operating States & Output Modes
E
The Zone Input Switch Tolerance(Ttol) is the tolerance on when the zone switching circuitry is actually
able to start the switching of the inputs.
Besides T
tol and Tdelay, there is an additional delay of up to Tsample before the change on the zone set
select inputs is recognized.
Therefore, assuming switching of the inputs starts at t
start, the system is guaranteed to switch zones
between t
min = tstart + Tdelay - Ttol and tmax = tstart + Tdelay + Ttol + Tsample.
Fig. 2-10 Zone set select input switching and zone set switch.
How To Configure Input Switch Circuitry Timing
Relative to tstart, the longest time it will take to begin monitoring Zone set B is tmax. When you take into
account the scanner's response time required to actually detect an object present in Zone set B, the
longest time to turning off the OSSDs relative to t
start can be shown as:
t
maxToOff = tmax + Tresponse
The critical timing guarantee to be met when changing zone sets is tDangerZoneB. The input switching
circuitry should begin switching the zone set select inputs prior to t
DangerZoneB to ensure Zone B is
activated early enough to detect an object previously present in the zone set. The amount of time prior
to t
DangerZoneB to start switching can be derived from tmaxToOff by equating it to tDangerZoneB.
t
start = tDangerZoneB - (Tresponse + Tdelay + Ttol + Tsample)
This means the switching circuitry must be configured to begin switching the inputs T
maxReaction before
t
DangerZoneB to ensure safe monitoring of Zone set B, where
T
maxReaction = Tresponse + Tdelay + Ttol + Tsample
If tstart (switching start time) is configured without consideration of TmaxReaction (total maximum reaction
time), object detection within the new safety zone after switching and turning OFF of the safety outputs
may be delayed.
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