Watlow Series 988 - Manual (Page 133)

WATLOW Series 988 User’s Manual 8.17 General Software Features, Chapter 8
General Software
Sample Application
An engineer needs to control the temperature of a muffle furnace. The fur-
nace set point must be ramped up at a defined rate to prevent stressing
the muffle and other system components. By enabling the ramp to set
point function in the Series 988, the engineer can control the rate at
which the set point will rise. Ramp to set point is enabled in the Global
Menu using the Ramping Function prompt
[``rp]. To ramp on start up
only, select start [Strt]. To ramp on start up and on any set point
changes, select set point [StPt]. The ramp rate [rate] is in degrees per
minute.
For further protection of the system, output 2, 3 or 4 can be configured as
a rate alarm, monitoring the rate of increase or decrease in the process
variable on input 1. The Alarm Low
[A2LO] and Alarm High [A2HI]
prompts (The “2” in these examples refers to output 2.) establish the
ramp-down and ramp-up rate set points, respectively, in degrees per
minute.
TL W WA
PROCESS
L1 L2 L3 L4
DEV
% OUT DISPLAY
MODE
AUTO
MAN
SERIES 988
input 1 output 1
limit
limit
sensor
temperature
sensor
heaters
heaters
Muf f le Furna c e
Figure 8.17 -
Muffle furnace with
ramp to set point.