Watlow PPC-2000 - Manual (Page 132)

Chapter 3: Operating with AnaWin 3 PPC-2000 User’s Guide
108 Watlow Anafaze Doc.# 30002-00 Rev 2.3
Table 3.10 Secondary Channel Parameter
Settings
As the temperature in the middle of the tank (channel 1) drops,
the output goes up proportionally and the set point of channel
2 goes up proportionally. Thus heat is added to the system at
the element even though the temperature near the element
may have been at the desired temperature.
With proportional control, when channel 1 is at set point, its
output is 0%, and the set point of channel 2 is equal to the
desired temperature 150°F. If the temperature of the channel 1
drops below 149°F, the deviation results in a proportional
output of 10%. This results in an increase to the set point for
channel 2 equal to 10% of the set point range. The set point
range is defined by Max Set Point - Min Set Point. In this case the
range is 40°F (190°F - 150°F = 40°F). Ten percent of 40°F is 4°F.
So when the temperature at channel 2 drops 1 degree, channel
2’s set point increases by 4°F to 154°F. For every degree
channel 1 drops, channel 2’s set point increases by 4°F until
channel 1’s output is 100% and channel 2’s set point is 190°F.
At this point further decreases to channel 1’s process variable
have no additional affect on channel 2. Figure 3.9 on page 109
illustrates this relationship.
Parameter Setting Description
PV Source PPC1:AI 1.2 The outer TC is selected for the secondary channel.
Set Point Source Channel 1 Out
For cascade control, the primary channel’s output
determines the secondary channel’s set point.
Min Set Point 150°F
When the primary channel’s output is 0% the
secondary channel’s set point is 150°F.
Max Set Point 190°F
When the primary channel’s output is 100% the
secondary channel’s set point is 190°F.
Heat Prop Band
The secondary channel’s PID parameter values may be determined by
autotuning or manual tuning.
Heat Integral
Heat Derivative
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