Mitsubishi Electric 800 Series Instruction Manual page 503

(A) Application parameters
Calibration of PID display bias and gain (Pr.934 to Pr.935)
• When both Pr.934 and Pr.935  "9999", the bias and gain values for the set point, measured value and deviation in PID
control can be calibrated.
• "Bias"/"gain" function can adjust the relation between PID displayed coefficient and measured value input signal that is
externally input.
Examples of these measured value input signals are 0 to 5 VDC, 0 to 10 VDC, or 4 to 20 mADC.
• Set the value that is displayed when the PID measured value (control amount) is 0% to Pr.934 and the value that is
displayed when the PID measured value (control amount) is 100% to Pr.935.
• When both of Pr.934 and Pr.935 "9999" and Pr.133 is set as the set point, the setting of Pr.934 is treated as 0%, and
Pr.935 as 100%.
• There are three methods to adjust the PID display bias/gain.
(a) Method to adjust any point by application of a current (voltage) to the measured value input terminal
(b) Method to adjust any point without application of a current (voltage) to the measured value input terminal
(c) Method to adjust only the display coefficient without adjustment of current (voltage)
(Refer to page 402 for details on (a) to (c), and make the necessary adjustments by considering Pr.905 as Pr.935 and Pr.126
(Pr.905) as Pr.935.
NOTE
• Always calibrate the input after changing the voltage/current input specification with Pr.73 and Pr.267, and the voltage/
current input selection switch.
• Take caution when the following condition is satisfied because the inverter recognizes the deviation value as negative
(positive) value even though a positive (negative) deviation is given: Pr.934 (PID bias coefficient) Pr.935 (PID gain
coefficient)
To perform a reverse action, set Pr.128 PID action selection to forward action. Alternatively, to perform a forward action,
set Pr.128 to reverse action.
Pr.934  Pr.935 (normal setting)
Reverse action
Forward action
PID output shutoff release level
(Example) Set the following: Pr.934="500", 20% (4 mA is
applied), Pr.935="100", 100% (20 mA is applied).
When the set point=400 and the measured value=360, the
deviation is +40 (>0), but the inverter recognizes the
deviation as -10% (<0). Because of this, operation amount
does not increase in the reverse operation setting.
The operation amount increases when the forward operation
is set.
To perform PID output shutoff release at deviation of +40 or
higher, set Pr.577="960".
502
PARAMETERS
100
Bias
Pr.934
0 20
0 4
Frequency setting signal
0 1
0 2
Pr.934
Reverse action setting to Pr.128 Reverse action
Forward action setting to Pr.128
Pr.577 -1000
Initial value
Gain
Pr.935
100%
20mA
5V
10V
Pr.935
Pr.934  Pr.935
Forward action
PID output shutoff release level
Set point
Deviation +40
Measured value
∗ ( ) indicates the deviation value
which the inverter can recognize
Forward action setting to Pr.128
Reverse action setting to Pr.128
1000 -Pr.577
500
400
360
100
0
20%
(0%) (25%) (35%)
Deviation -10%
100%
(100%)