Yokogawa Button Operated MV2000 - Manual (Page 220)

10-6 M-4660
10.2 Writing Expressions
This section defines expressions and explains how to write them.
Common Items
Follow the rules below when writing expressions.
• Use up to 120 characters to write expressions.
• Use parentheses to indicate the order of mathematical functions.
• Specify channels in an expression using channel numbers.
Examples: 1, 12, 101, and 201
• You can write the one digit numbers of constants (K), communication input data (C),
remote input terminal statuses (D), pulse inputs (P, Q), internal switch statuses (S),
alarm output relay statuses (I), and flags (F) in an expression using two digits or one
digit. For example: 01 or 1.
Examples: K01, K1, C01, C1, D01, D1, P01, P1, Q01, Q1, S01, S1, I01, I1, F01, and F1
• Be aware that the data of the previous scan is used for the computation channel’s
value and for the values of channels with numbers that are greater than the
computation channel’s number.
• Write special computations (HOLD, RESET, and CARRY) and conditional expressions
at the beginning of an expression.
Order of Precedence for Computations
The order of precedence for computations in an expression is as follows:
Type Operators and Functions
(High order of precedence)
Functions ABS(), SQR(), LOG(), LN(), EXP(), TLOG.MAX(), TLOG.MIN(),
TLOG.AVE(), TLOG.SUM(), TLOG.P-P(), CLOG.MAX(), CLOG.
MIN(), CLOG.AVE(), CLOG.SUM(), CLOG.P-P()
Special computations and conditional expressions
PRE, HOLD, RESET, CARRY, [a?b:c]
Power **
Logical negation NOT
Multiplication and division *, /
Addition and subtraction +, –
Greater than and less than .GT., .LT., GE., LE.
Equal and not equal .EQ., .NE.
Logical product AND
Logical sum and exclusive logical sum OR, XOR
(Low order of precedence)
Limitations
Expressions have these limitations.
Expression Limitations
TLOG computation An operator or function cannot be written inside the parentheses.
An expression can contain only one TLOG function.
CLOG computation The maximum number of channels that can be written in the parentheses is 30.
An operator or function cannot be written inside the parentheses.
An expression can contain only one CLOG function.
PRE An operator or function cannot be written inside the parentheses.
HOLD(a):b Can only be written at the beginning of an expression.
An expression can contain only one HOLD function.
RESET(a):b Can only be written at the beginning of an expression.
An expression can contain only one RESET function.
CARRY(a):b Can only be written at the beginning of an expression.
An expression can contain only one CARRY function.
Only TLOG.SUM can be specified for b.
Conditional
expressions [a?b:c] RESET, CARRY, and HOLD cannot be specified for a, b, and c.
Conditional expressions cannot be combined with other operators or functions
([a?b:c]+001 for example). However, a conditional expression can be specified for a, b,
and c.