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User Manual
GFK-1503F
Words
13
(Address +
12)
PID Built-in Function Block
Parameter/Description
Config Word
The low 6 bits of this word are used to modify default PID
settings. The other bits should be set to 0.
Bit 0: Error Term Mode. When this bit is 0, the error term
is SP - PV. When this bit is 1, the error term is PV - SP.
Setting this bit to 1 modifies the standard PID Error Term
from the normal (SP – PV) to (PV – SP), reversing the sign
of the feedback term. This mode is used for reverse acting
controls where the CV must go down when the PV goes
up.
Bit 1: Output Polarity. When this bit is 0, the CV output is
the output of the PID calculation. When it is set to 1, the
CV output is the negated output of the PID calculation.
Setting this bit to 1 inverts the Output Polarity so that CV
is the negative of the PID output rather than the normal
positive value.
Bit 2: Derivative action on PV. When this bit is 0, the
derivative action is applied to the error term. When it is set
to 1, the derivative action is applied to PV only.
Bit 3: Deadband action. When the Deadband action bit is
0, the actual error value is used for the PID calculation.
When the Deadband action bit is 1, deadband action is
chosen. If the error value is within the deadband limits,
the error used for the PID calculation is forced to be zero.
If, however, the error value is outside the deadband limits,
the magnitude of the error used for the PID calculation is
reduced by the deadband limit (|error| = |error –
deadband limit|).
Bit 4: Anti-reset windup action. When this bit is 0, the anti-
reset-windup action uses a reset (integral term) back-
calculation. When the
output is
accumulated integral term is replaced with whatever
value is necessary to produce the clamped output exactly.
When the bit is 1, the accumulated term is replaced with
the value of the integral term at the start of the
calculation. In this way, the pre-clamp integral value is
retained as long as the output is clamped. This option is
not recommended for new applications. See "CV
Amplitude and Rate Limits" on page 14-15.
Bit 5: Enable derivative filtering. When this bit is set to 0,
no filtering is applied to the derivative term. When set to
1, a first order filter is applied. This will limit the effects of
higher frequency process
measurement noise, on the derivative term.
Setting Config Word: Set Config Word to 0 for default
operation. Add 1 (16#0001) to set bit 0, add 2 (16#0002)
to set bit 1, add 4 (16#0004) to set bit 2, add 8 (16#0008)
to set bit 3, add 16 (16#0010) to set bit 4, and add 32
(16#0020) to set bit 5. For example, to set bits 0, 3 and 5
only, set Config Word to 1 + 8 + 32 = 41 (16#0029). Some
users will find the Config Word value easier to interpret in
hexadecimal (16#) format.
Low Bit
Units
Low 6 bits
used
clamped, the
disturbances,
such
as
Chapter 14
Jan 2020
Range
Boolean
256
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