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Terminology and Function Descriptions Section 2-4
Measurements will not be stable if the difference is less than 2.5 A. If
the difference is less than 2.5 A, wrap the wire around the CT two or
three times to increase the measured current. The heater current mon-
itor function can be used to measure the currents. Actual values can
vary from calculated values.
Input Shift Value • An input shift value can be set to offset the indicated value from the actual
measured value. For example, if the input shift value is set to 3.0
°C and
the actual measured temperature is 50
°C, the monitored temperature will
be 53
°C.
• If the input shift value is set too large, a sensor error can occur near the
upper and lower limits of the temperature range even though the measure
temperature is still within range.
Autotuning (AT) PID calculations using the limit cycle method are performed when autotuning
is executed. Parameters cannot be written for loops that are currently being
autotuned.
• The limit cycle method causes hunting using ON/OFF control near the set
point to measure the hunting cycle and amplitude and uses the results to
make calculations for PID control.
• Be sure to change the START AT command in the output word after the
START AT command has been sent and received. If the START AT com-
mand is left set in the output word, autotuning will be executed again as
soon as it is completed.
Hunting cycle
Set point
AT executed for ON/OFF control
AT completed (ampli-
tude and hunting cycle
measurements com-
pleted)
Amplitude
Calculated
PID control
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