The 3 parameters of a PID controller are
P - Proportional, I - Integral, and D - Derivative
The output percent is determined by the formula P*((Setpoint - ActualRate)/MaxRate +
I * (integral of the proportional term) +
D * (derivative of the proportional term))
In this controller, the D term is zero. The proportional term is scaled so that a term of P = 100 yields 1 percent
of output change for each 1 percent of error.
The integral term is scaled so that I = 100 yields a time constant of 1 second. The time constant is inversely proportional to
the I parameter, so that I = 10 yields a time constant of 10 seconds.
The seven rate calibration pairs of output percent and output rate are used to set the
initial output percent when the unit STARTs. Also, the MaxRate is used in the PID equation above.
The "zero output rate" is fixed at 0.0, and the "max output percent" is fixed at 100%. The other parameters can be edited.
Example:A calibration pair of 25%, 250 means that a rate of 250 weight units per unit time will be obtained when the output percent is 25 %.
If a 2 Point Auto Rate Calibration is selected, the unit will go to the high rate output percent for a period of feed time plus prime time
When this period is complete, it will save the actual rate into the high cal rate
It will then pause for a period of pause time, and then go to the low rate output percent for a period of feed time
When this period is complete, it will save the actual rate into the low cal rate
Selecting the STOP button during rate calibration pause will allow the feed hopper to be manually refilled. Pressing the RESUME button after the refill will resume the calibration.
Pressing STOP when not paused will abort the calibration.
After doing the auto rate calibration at the low and high rates, the unit will estimate the zero rate output percent and the
Max rate cal rate. , and will fill values for the first, third, and fifth five point calibration rate pairs.
If an Advanced calibration is selected, the user must enter calibration pairs for the low rate and the high rate. The unit will fill in the other calibration
pairs based on linear extrapolation from the two entered points.
If a 5 point calibration is selected, the user must enter the 5 Point Calibration point 1 output percent. This first point must be between 0.0 and 30.0 percent. The next 4 calibration output percents are fixed at
cal point 1 + 10.0, cal point 1 + 20.0, cal point 1 + 30.0, and cal point 1 + 60.0. The unit will then run at each of these output percents, starting with the highest one, for a period of feed time, or of feed time
plus prime time on the first run. It saves the actual rates it observes into the cal rates, and estimates the MaxRate and zero output rates.