( 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).)
Determine the set point.
Determine the set point of the item
to be adjusted.
Convert the set point into %.
Calculate the ratio of the set point
to the detector output.
Set the set point.
Enter a voltage to across
terminals 2-5 according to the set
Set the proportional band and
integral time to slightly higher
values and the differential time to
a slightly lower value, and switch
on the start signal.
Is the process
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.
* When calibration is required, use Pr. 902 to Pr. 905 to calibrate the
detector output and set point setting input in the PU mode during an
Set the room temperature to 25°C (77°F)
Set "20" or "21" in Pr. 128 to enable PID control.
When the detector used has the specifications that 0°C (32°F)
is equivalent to 4mA and 50°C (122°F) to 20mA, the set point of
25°C (77°F) is 50% because 4mA is equivalent to 0% and
20mA to 100%.
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 a slightly
lower value. In accordance with the system operation, reduce
the proportional band and integral time and increase the
While the process value is steady, the
proportional band and integral time may
be reduced and the differential time
increased throughout the operation.