Baumer BA Scatec10 15 - Manual (Page 17)

User manual Scatec-10 / -15 17 / 44 Baumer Electric AG
Version 2011-03 www.baumer.com Frauenfeld, Switzerland
There are three different types of dead time depending on how the dead time is
specified.
Dynamic dead time (00 = dyn):
The length of the dead time corresponds to a certain percentage of the mean
interval between copies.
If dynamic dead time is set as the suppression mode, then the percentage will be
set subsequentely in menu C4 (dead time %) . The mean interval between copies is
calculated continuously by the internal micro controller of the Scatec-10 / -15 itself
and is therefore simultaneously adapted to changes of the conveyor speed. This
type of dead time is recommended as long as there is no possibility to synchronize
the Scatec. With dynamic dead time as the suppression mode, occasionally, a
counting error may occur if the lap-stream starts up very quickly from a standstill
(particularly if the conveyor belt initially runs with no load and accelerates to
maximum speed before copies appear on the conveyor belt) or when the conveyor
belt stops abruptly. Do not use the dynamic dead time mode if the lap stream is
highly irregular (i.e. highly varying intervals between copies). Taking single copies
out of the otherwise regular lap stream does not cause any problems.
Synchronous dead time (01 = sync):
The output does not become active again until the conveyor has run a
defined distance (regardless of the time it takes the conveyor to do this!).
Scatec-10 / -15 can be connected to an encoder, which permits synchronization of
the sensor to the conveyor speed. The big advantage of synchronization is that a
false pulse suppression mode can be set which is completely independent of the
conveyor speed, because now the output is set inactive not for a specific time but for
a specifc distance. In the synchronous dead time mode, the output is not set active
again until the conveyor has run the dead path defined in menu C6. For example,
the problem of multiple pulses generated by vibrations if the conveyor comes to a
stand still with an edge exactly in the laser beam can be easily solved this way.
Note: Whenever possible, use the synchronous dead time mode!
If in menu C3 the synchronous dead time mode has been choosen, then
subsequently in menu C5 the encoder resolution in millimeters per encoder pulse, in
menu C6 the dead path, and in menu C7 the type of encoder (encoder with A/B-
channel or A-channel only) has to be set. Based on the values for the encoder
resolution and the dead path, the sensor will calculate internally for how many
encoder pulses possible false pulses will be suppressed. Note, that with encoder
type A/B choosen, the direction of transportation is taken into account. After an
edge, the output is not set active again until the conveyor has run the dead path in
the forward direction. If a Scatec-10 / -15 with C7 set on (encoder with A/B-channel)
does not give out any pulses although it detects edges (amber LED lights up), then
the connections of the A/B channels have been mixed up. In his case the application
software ScaDiag would display the warning “conveyor in reverse”.
Fixed dead time (02 = fixed):
The length of the dead time is set to a fixed value in milliseconds.
Note: A fixed dead time imposes a limit to the maximum counting rate in the same
way as the output pulse length. The same rule of thumb given in the describtion of
C0 applies also to the fixed dead time, just substitute output pulse length by fixed
dead time.
Retro-reflective foil only (03 = refl):
The Scatec-10 / -15 reacts only to the retro-reflective foil and no longer to
any edges.
Because the Scatec-10 / -15 is equipped with a retro-reflective sensor, the sensor
can unambiguously detect gaps in a lap stream, provided that there is a retro-
reflecting tape (part number: FTDF 020F020) mounted as a beam blocker. This
built-in retro-reflective sensor allows for a counting mode on its own. In the reflective
mode, Scatec- / -15 no longer detects edges, but reacts only to shadowing the
retro-reflecting tape. As soon as the laser beam no longer strikes the retro-reflecting