Instruction manual

141
4
PARAMETERS
(7) Calibration example
(A detector of 4mA at 0°C (32°F) and 20mA at 50°C (122°F) is used to adjust the room
temperature to 25
°C (77°F) under PID control. The set point is given to across inverter
terminals 2-5 (0-5V).)
Convert the set point into %.
Determine the set point.
START
Determine the set point of the item
to be adjusted.
Calculate the ratio of the set point
to the detector output.
Calibration.
Set the set point.
Enter a voltage to across
terminals 2-5 according to the set
point (%).
Operation
Set the proportional band and
integral time to slightly higher
values and the differential time to
9999 (No control), and switch on
the start signal.
Is the process
value steady?
Adjust parameters.
Set the proportional band and integral
time to slightly higher values and set
the differential time to a slightly lower
value to stabilize the process value.
Optimize parameters.
While the process value is steady, the
proportional band and integral time may
be reduced and the differential time
increased throughout the operation.
END
Yes
No
When the set point setting input (0 to 5V) and detector output
(4 to 20mA) must be calibrated, make the following calibration
∗
.
Set point = 50%
Since the specifications of terminal 2 are such that 0% is
equivalent to 0V and 100% to 5V, enter 2.5V into terminal 2.
……
For PU operation, set the set point (0 to 100%) in Pr. 133.
During operation, set the proportional band and integral time to
slightly higher values and set the differential time to 9999 (No
control). In accordance with the system operation, reduce the
proportional band and integral time. For slow response system
where a deadband exists, differential control shuold be turned
on and increased slowly.
∗ When calibration is required, use Pr. 902 and Pr. 903 (terminal 2) or
Pr. 904 and Pr. 905 (terminal 4) to calibrate the detector output and
set point setting input in the PU mode during an inverter stop.
……
……
……
……
Set the room temperature to 25
°
C (77
°
F)
Set "20" or "21" in Pr. 128 to enable PID control.
Detector specifications
When the detector used has the specifications that 0
°C (32°F)
is equivalent to 4mA and 50
°C to 20mA, the set point of 25°C
(77
°F) is 50% because 4mA is equivalent to 0% and 20mA to
100%.
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