Rockwell Automation 900-TC32 Digital Temperature Controllers, Series B - Manual (Page 87)

Publication 900-UM007D-EN-E - January 2011
Configuration & Basic Operation 3-17
Configuring the Output
Parameters Control Period
The Control Period parameter is used in the PID control method and allows
you to adjust the minimum amount of time between ON cycles of the
ON/OFF output (MV). This is sometimes referred to as timed proportional
PID control.
Figure 3.19 — Control Period Parameter
A shorter period may provide better ON/OFF control performance. We
recommend setting the control period to 20 seconds or more. In the case of
electromechanical relay outputs, doing this will improve its life expectancy. If
you are using an ON/OFF voltage output (SSR) setting, a shorter time will not
drastically impact the life of the SSR, since it is rated by the number of ON
hours. If necessary, readjust the Control Period by trial operation to meet the
needs of your application.
• You can configure the individual control period values in the Control
Period (HEAT) and Control Period (COOL) parameters (Initial Setting
function group). Note: The default is 20 seconds.
• The Control Period (COOL) parameter can be used only in the heating
and cooling control method.
• When Control Output 1 is used as an analog current output, the Control
Period (HEAT) parameter cannot be used.
Note: The Control Period parameter allows what is typically called Time
Proportioning ON/OFF Control to be done in the 2-PID method.
Direct/Reverse Operation
Figure 3.20 — Direct/Reverse Operation
Direct operation refers to control where the manipulated variable (MV) is
increased according to the increase in the process value (PV). Alternatively,
reverse operation refers to control where the manipulated variable (MV) is
decreased according to the increase in the process value (refer to Figure 3.21).
Direct/reverse operation can be used in ON/OFF or PID control.
Control
period
(OUT1)
Control
period
(OUT2)
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