Watlow CPC400 - Manual (Page 72)

Chapter 3: Operation and Setup CPC400 Series User’s Guide
58 Watlow Anafaze Doc. 0600-2900-2000
the PID parameters to determine when control switches be-
tween heating and cooling.
How to Set Up Closed-Loop Control
The following are the basic steps to set up closed-loop con-
trol for a typical control loop:
1. Use the Input menu to specify the type of input signal
and, if necessary, how to scale that signal.
2. If using on/off or both heat and cool outputs, use the
Control menu to specify the control hysteresis.
3. Use the Output menu to enable the heat and/or cool
outputs and to specify the control output signal form.
4. Enter a set point. See Changing the Set Point on page
54.
5. Put the channel in Tune mode. See Changing the Con-
trol Mode and Output Power on page 55.
For more information about the setup menus and parame-
ters, see Chapter 5, Menu and Parameter Reference.
Setting Up a Process or Pulse Input
If you use a process or pulse input signal, you must set up
scaling parameters in the Input menu to scale the raw in-
put signals to the engineering units of the process.
Input Scaling
To scale the input, you enter values that represent two
points on a conversion line. Each point indicates an input
signal level and the corresponding process value.
For a pulse input, the input signal range is 0 to 2000 Hz.
For a process input, the input signal is expressed as per-
cent of full range. For example, for a 0 to 20 mA process in-
put, 0 mA is 0 percent, 10 mA is 50 percent, and so on.
The conversion line scales the input signal to the engineer-
ing units of the process. For example, in Figure 3.6, a 20
percent input signal corresponds to 8 pounds per square
inch (PSI), and a 100 percent signal corresponds to 28 PSI.