Mitsubishi Electric FR-A820-00046 Instruction Manual Page 718

(A) Application parameters
Calibration example
Adjust room temperature to 25 °C by PID control using a detector that outputs 4 mA at 0 °C and 20 mA
at 50 °C.)
Determination of set point
Determine the set point of what is
desired to be adjusted.
Conversion of set point into %
Calculate the ratio of the set point to
the detector output.
Setting of set point
Input a voltage across terminals 2–5
according to the set value %.
Operation
Set the proportional band (Pr. 129) to
a slightly larger value, the integral time
(Pr. 130) to a slightly longer time, and
the differential time (Pr. 134) to "9999"
(no function), and turn ON the start
signal.
To stabilize the measured value,
change the proportional band (Pr. 129)
to a larger value, the integral time
(Pr. 130) to a slightly longer time, and
the differential time (Pr. 134) to a
slightly shorter time.
Fig. 5-266:
5 - 538
Start
Make calibration.
Is the set point stable?
No
Calibration example
Set the room temperature to 25 °C
Set Pr. 128 and turn ON the X14 signal to enable PID control.
Detector specifications
When 0 °C → 4 mA and 50 °C → 20 mA are used, the set point 25 °C
is 50 % on the assumption that 4 mA is 0 % and 20 mA is 100 %.
Make the following calibration* when the target setting input (0 to
5 V) and detector output (4 to 20 mA) must be calibrated.
To set the set point to 50 % using voltage input
The terminal 2 specification is 0 V for 0 %, and 5 V for 100 %.
Thus, to set to 50 %, input 2.5 V to the terminal 2.
To set the set point to 50 % using parameters
Set Pr. 133 = "50". (If C42 (Pr. 934) and C44 (Pr. 935) ≠ "9999", set
"25 (no % conversion)" directly in Pr. 133.)
When performing operation, first set the proportional band (Pr. 129)
to a slightly larger value, the integral time (Pr. 130) to a slightly longer
time, and the differential time (Pr. 134) to "9999" (no function), and
while looking at the system operation, decrease the proportional
band (Pr. 129) and increase the integral time (Pr. 130).
For slow response system where a deadband exists, differential
control (Pr. 134) should be turned ON and increased slowly.
Yes
Parameter optimization
While the measured value is stable
throughout the operation status, the
proportional band (Pr. 129) may be
decreased, the integral time (Pr. 130)
decreased, and the differential time
(Pr. 134) may be increased.
Parameters
I001237E  