Yokogawa Touch Screen GP20 - Manual (Page 73)

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IM 04L51B01-01EN
Configuring the GX/GP
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App
Special Computations
PRE( )
(Syntax) PRE(e1)
(Condition) Determines the previous value of e1.
HOLD(a):b
(Syntax) HOLD(a):b
(Condition) When a is zero, b is carried out to derive the computed value. Otherwise, the
previous computed value is held.
Expression Example
Under normal conditions, TLOG.SUM(0001) is carried out to derive the computed value.
When [0001] exceeds K01, the previous computed value is held.
HOLD(0001.GT.K001):TLOG.SUM(0001)
K001
RESET(a):b
(Syntax) RESET(a):b
(Condition) When a is zero, b is carried out to derive the computed value. Otherwise,
the previous computed value of b is reset, and b is carried out to derive the
computed value.
Expression Example
Under normal conditions, TLOG.SUM(0001) is carried out to derive the computed value.
When [A001] exceeds K01, the previous computed value is reset, and TLOG.SUM(0001)
is carried out.
RESET(A001.GT.K001):TLOG.SUM(0001)
K001
Reset
CARRY(a):b
(Syntax) CARRY(a):b
(Condition) Only TLOG.SUM can be specified for b. If the computed value X of b is
less than a, the computed result is X. If X is greater than or equal to a, the
computed result is the excess (X – a).
(Explanation) When a value such as the flow rate is summed and the threshold value is
reached or exceeded, the sum value is reset while carrying over the amount
that exceeded the threshold value.
Expression Example
Expression that sums the values of channel 0001 and resets the value when it reaches or
exceeds 10000.
K001=10000
CARRY(K001):TLOG.SUM(0001)
K001
Examples of Equations That Are Not Allowed
0002+HOLD(K001):TLOS.SUM(0001)
Reason: HOLD is not at the beginning of the expression.
RESET(A001.GT.K001):TLOG.SUM(0001)+RESET(A001.GT.K001):0002
Reason: RESET appears twice in one equation.
1.5 Configuring Math Channels