Watlow CLS - Manual (Page 108)

100 CLS User’s Guide
PID Tuning and Control
Proportional, Integral and Derivative Control
For an improved level of control, use Derivative control with
Proportional or Proportional and Integral control. Derivative control
corrects for overshoot by anticipating the behavior of the process
variable and adjusting the output appropriately. For example, if the
process variable is rapidly approaching the setpoint, Derivative control
reduces the output, anticipating that the process variable will reach
setpoint. Use it to eliminate the process variable overshoot common to
PI control. (This figure shows a process under full PID (Proportional,
Integral, and Derivative) control).
Control Outputs
The CLS provides a 5 Vdc digital output signal for PID control outputs.
These outputs normally control the process using relays. Watlow
Anafaze can also provide a Serial Digital to Analog converter (SDAC)
for 0-5 Vdc, 0-10 Vdc, or 4-20 mA analog output signals.
Digital Output Control Forms
The next section explains different modes for control outputs.
On/Off
On/Off output is very simple: it turns the output on or off according to
the control signal of the On/Off control.