Chapter 5: Control Functions and Operating Instructions
DTM temperature controller operating manual
Chapter 5
Control Functions and Operating Instructions
5.1 Control Functions
This device provides several control modes, including the following: PID, On_Off, programmable PID, Slope
control, Automatic/Manual switching.
5.1.1 Explanation of Control Functions
PID:
When set for heating or cooling output, the program will perform PID calculations on the present
value (PV) and setpoint value (SV), and output the results of calculations for use in temperature
control. When this function is used, PID parameters and a control cycle must be set, or auto-
tuning (AT) performed to automatically generate these parameter values.
A. Setting PID parameters and control cycle: PID parameters can be manually adjusted in
accordance with system characteristics or generated automatically via auto-tuning. The
control cycle refers to the PID computation cycle; if the control cycle is 10 seconds, one
PID value is calculated every 10 seconds, and the result is output for use in temperature
control.
Notes:
1. If systems heating rate is fast, the control cycle cannot be set to be too long.
2. If the output is a relay output, frequent actions will shorten the life of the relay. It is
recommended that the control cycle be set to more than 20 seconds.
B. Proportional control error compensation: When I parameter is set to 0, the Output power
offset parameter can be adjusted to reduce the error of temperature control.
C. Dual output: One is the heating output, and the other is the cooling output; these two PID
parameters are mutually independent.
If there are two outputs, one can be set as heating, and the other can be set as cooling, which
allows a Deadband to be set (as shown in the figure below). This parameter will be automatically
generated when in dual output control. The goal of this operation is to avoid waste of energy
from too frequent heating / cooling control.
When using PID heating and cooling control, the PID calculated output <0% indicates cooling
output; the PID calculated output >0% indicates heating output.
For example: When the Deadband is set to 2.0%, it means that the output will not work when
the PID calculation output is between -1% and 1%.
For example: When the Deadband is set to -10.0%, it means that the heating and cooling outputs
will act simultaneously when the PID calculation output is between -5% and 5%.
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