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WATLOW Series 988 User’s Manual 8.3
General Software Features, Chapter 8
General Software
TL
W
W
A
PROCESS
L1 L2 L3 L4
DEV
% OUT
DISPLAY
MODE
AUTO
MAN
SERIES 988
input 1 output 1
QPAC
with
QCD
input
limit
Semiconductor Oven
temperature
sensor
limit
sensor
heated platen
50% output
1 on, 1 off
10% output
1 on, 9 off
100% output
10 on, 0 off
66% output
2 on, 1 off
Sample Application
A Series 988 controls a heated platen in a semiconductor oven. Previously
it used a power control requiring a 4-20mA signal to implement burst-fire
control. We have replaced the power control with a Watlow Loyola QPAC
with a QCD card that accepts a signal directly from an open-collector out-
put of the Series 988. This gives smooth control at a lower overall system
cost.
Figure 8.3b -
Semiconductor
oven with burst fire.
Figure 8.3a - Sine
waves of burst fire
settings.