21/33
When the temperature is 5 degree below the set point, the output is 71%. When the
temperature is equal to the setting, the controller will have 0% output (assuming integral
and derivative functions are turned off). This constant also affects both integral and
derivative action. Smaller P values will make the both integral and derivative action
stronger. Please note the value of the P is temperature unit sensitive. If you found an
optimized P value when operating the controller in Fahrenheit, to use in Celsius, that
optimized P value needs to be divided by 1.8. This controller will automatically convert
the current P value if you change the temperature display unit.
Note 7. I:
Integral Time. The unit is in seconds. This parameter controls the output of
controller based on the difference between the measured and set temperature integrated
with time. For example, if I = 1000, it means if the temperature difference between the
cabinet temperature and set temperature stays constant, the output will be doubled after
1000 seconds. Integral action is used to eliminate temperature offset.
The larger the I
value, the slower the action.
E.g. assuming the difference between the measured and
set temperature is 2 degrees and remain unchanged, the output will increase
continuously with time until it reaches 100%. When the temperature fluctuates regularly
(system oscillating), it increases the integral time. Decrease it if the controller is taking
too long to eliminate the temperature offset. When I = 0, the system becomes a PD
controller. For very slow response systems, such as slow cooker and large commercial
rice cooker, setting I = 0 will significantly reduce the temperature overshoot.
Note 8. d:
Derivative Time. The unit is in seconds. Derivative action contributes the
output power based on the rate of temperature change. Derivative action can be used to
minimize the temperature overshoot by responding its rate of change. The larger the
number is, the stronger the action will be. For example, when the door of oven is opened,
the temperature will drop at very high rate. The derivative action changes the controller
output based on the rate of change rather than the net amount of change. This will allow
the controller to act sooner. It will turn the heater to full power before the temperature
drops too much.
Note 9. T:
Control Cycle Time. The unit is second. This unit determines how long for the
controller to calculate each action. For example, if T is set to 10 seconds, when controller
decide the output should be 10%, it will turn on the heater 1 second for every 10 seconds.
This parameter should be set at 2 second for heating with an electric heater.
Note 10. Auto-tune:
This parameter can be used to initial the auto-tune process. Set
Auto-tune to ON then press SET key to confirm. Once exit (in normal display mode), the
display will flash alternately between normal display and auto-tune notification
(Auto-tuning Please wait…), which indicates auto-tuning is in progress. When the display
stops flashing, the auto-tuning process is finished. Now, the newly calculated PID
