2-411
2 Instruction Descriptions
NJ-series Instructions Reference Manual (W502)
Conversion Instructions
2
PIDAT
• If hunting continues too long, increase ProportionalBand or increase IntegrationTime.
• If rapid hunting occurs, decrease DerivativeTime.
If you use the PIDAT instruction for temperature control, use the following initial values of the PID con-
stants as reference. Use the default values for the other variables.
* If you perform autotuning, use the results from autotuning.
• The values of PV and SP must be between the values of RngLowLmt and RngUpLmt, inclusive. Align
the units of these variables as shown below.
* MAX: Upper limit of input range in physical units, MIN: Lower limit of input range in physical units,
• The following table shows which variables can be changed depending on the operating status.
Initial PID Constants for Temperature Control
Variables Initial values (reference values)*
ProportinalBand 10%FS
IntegrationTime 233 s
DerivativeTime 40 s
Precautions for Correct Use
Unit Values of PV and SP
Values of RngLowLmt and
RngUpLmt
% FS PV = (Process value in physical units − MIN)/(MAX − MIN) × 100
SP = (Set point in physical units − MIN)/(MAX − MIN) × 100*
RngLowLmt = 0
RngUpLmt = 100
Physi-
cal unit
PV = Process value in physical units
SV = Set point in physical units
RngLowLmt = MIN
RngUpLmt = MAX*
Variables
Control status
Instruction execution
stopped
*1
Automatic operation
when autotuning is not
being executed
*2
Automatic operation
when autotuning is being
executed
*3
Run Possible Possible Possible
ManCtl Possible Possible Possible
StartAT Possible Possible Possible
PV Possible Possible Possible
SP Possible Possible Not possible
MVLowLmt Possible Possible Not possible
MVUpLmt Possible Possible Not possible
ManResetVal Possible Possible Not possible
MVTrackSw Possible Possible Not possible
Time
Increase ProportionalBand or increase IntegrationTime.
PV
SP
Time
PV
SP
Decrease DerivativeTime.
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