Super Systems 9205 Series - Manual (Page 86)

Series 9205 Operations Manual Rev A 85
PID Loop Setup
PID is the tuning parameters entered for each Process Variable
loop.
Prop Band (0 for On/Off)
Proportional Band determines the response to the current error.
The Proportional Band is the percent of the range of the process
variable that will produce 100% output and is the inverse of the
proportional gain. A low Proportional Band value results in a
larger change in output for a given error. Conversely, a high
Proportional Band value results in a smaller change in output for a
given error. If the Proportional Band is too small, control may
oscillate or be otherwise unstable. If the Proportional Band is too
large the control action may be too sluggish in response to
changes within the system. Note: If the Proportional Band is set to
0.0, only on/off control is performed. The range 0 – 3276.0.
Reset
Reset determines the influence of past errors. The Reset, or
integral action (expressed in repeats per minute), sums the error
between the process variable and setpoint over time and adds this
accumulated output to the proportional output. A “proportional
only” controller generally operates with steady-state error
because some error is required to produce control output. The
goal of integral action is to drive the steady-state error to zero and
eliminate this droop. The range is 0 – 327.67.
Rate
Rate adjusts the response to future errors. The Rate, or derivative action (expressed in minutes), is used to
predict system behavior and has a dampening effect. The more the controller tries to change the process
variable the harder, the derivative will work to counter that effort. This dampening effect can be valuable in
reducing overshoot but is most often useful when trying to improve control on systems with significant and
predicable lag. The range 0 – 327.67. NOTE: The rate is not typically used for carbon control.
Mode
This is the mode of the loop. The values are: Dual Reverse, Single Reverse, Dual Direct, or Single Direct.
Dual – This has two output relays which can increase and decrease to achieve your SP.
Single – This has one relay which works in only one direction to achieve your SP.
Direct - If the PV - SP equals a positive number and the output would bring the PV down toward setpoint
that is direct.
Reverse – If the PV - SP equals a negative number and the output would bring the PV up toward setpoint
then that is reverse
Example: If a 12 mA output drives a 0 degree F temperature (PV) UP to a 1200 degree F temperature (SP),
this would be REVERSE , and since this would take a SINGLE output from the controller, the Mode for the
Temperature Loop is Single Reverse.
Integral Preset
This field provides an offset for the starting point for PID control, also referred to as “Load Line” or “Manual
Reset”. The range is –100 to 100.