10
by 1.8 when changed to Fahrenheit.
On/off mode
. If P is set to 0, the control mode will be changed from PID mode to
On/off mode. On/off mode should be used for controlling an external relay, a
solenoid valve, or a compressor of freezer. You also need to set the hysteresis
band (dead band) for the on/off mode. In the on/off mode, Integral and Derivative
parameters are not valid.
I. Integral time. The unit is in seconds. This parameter controls the output of the
controller based on the difference between the measured and set temperature
integrated with time. Integral action is used to eliminate temperature offset. Larger
numbers mean slower action. e.g. assuming the difference between the
measured and set temperature is 2 degree and remain unchanged, the output will
increase continuously with time until it reaches 100%. When temperature
fluctuates regularly (system oscillating), increase 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 those
with slow cookers and large commercial rice cookers, setting I = 0 will significantly
reduce the temperature overshoot.
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 to its rate of change. The
larger the number is, the faster the action will be. e.g. when the door of an oven is
opened, the temperature will drop at a 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
AT,
Auto-tuning
Every type of cooker has its own unique set of tuning parameters. For the
controller to heat with stability, it should have programmed with the tuning
parameters for the cooker currently being used.
When Should the Controller be Tuned?
The Auto-tuning function (it’s often known as self-tuning) can automatically
optimize the PID parameters for your chosen cooking system. The auto-tuning
function will heat up your cooker then let it cool down. It will repeat this heat/cool
cycle several times. Based on the response time of the whole cooking system, the
controller will calculate and set the PID parameters for your cooker.
