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(29)CH AT bias setting (Un\G53, Un\G85, Un\G117, Un\G149)
The point set as the set value (SV) in the auto tuning can be rearranged by using this buffer memory area.
The auto tuning function determines each PID constant by performing the two-position control toward the set
value (SV) and making a temperature process value (PV) hunting.
Set CH AT bias setting (Un\G53, Un\G85, Un\G117, Un\G149) when an overshoot caused by the hunting is
improper.
The auto tuning is performed with having the AT point (the point rearranged by the setting) as its center. When
the auto tuning is completed, AT bias is not added and a control is performed toward the set value (SV).
For details on the auto tuning function, refer to the following.
Page 176, Section 4.6
Ex.
When AT bias is set to minus value (reverse action)
(a) Setting range
The setting range is from (-(full scale)) to full scale. The setting range depends on the input range setting.
( Page 96, Section 3.4.2 (12))
Ex.
When the value of the buffer memory is set as follows
•CH Input range (Un\G32, Un\G64, Un\G96, Un\G128): 38 (temperature measurement range -200.0 to
400.0°C, resolution: 0.1)
The setting range is -6000 to 6000.
(b) Setting unit
The value to be set differs depending on the stored value in CH Decimal point position (Un\G1 to Un\G4).
( Page 86, Section 3.4.2 (2))
• No decimal place (0): Set a value in 1°C ( or digit) unit.
• One decimal place (1): Set a value in 0.1°C ( ) unit (tenfold value).
(c) Default value
The default values are set to 0 in all channels.
(d) Precautions
For CH AT bias setting (Un\G53, Un\G85, Un\G117, Un\G149), set the range where PID operation fluctuates
slightly and the control result get no effect.
Depending on the controlled object, accurate PID constants may not be obtained.
Common
Temperature process value (PV)
Time
Set value (SV)
AT point
CH AT bias setting
(Un\G53, Un\G85, Un\G117, Un\G149)