Watlow Electric 986 User Manual
WATLOW Series 988 User’s Manual
8.3
General Software Features, Chapter 8
General Software
TL
W
WA
PROCESS
L1
L2
L3
L4
DEV
% OUT
DISPLAY
MODE
AUTO
MAN
SERIES 988
input 1
output 1
QPAC
with
QCD
input
limit
S e mic onduc t or O v e n
temperature
sensor
sensor
limit
sensor
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.
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.
Semiconductor
oven with burst fire.
Figure 8.3a - Sine
waves of burst fire
settings.
waves of burst fire
settings.
C8.wc 5/14/1999 8:55 AM Page 8.3