ABB CM30 User Manual page 56

ControlMaster CM30 and CM50
Universal process controllers,
...Functions
Math Blocks
Math Block Number
Block Type
Equation
Real Time
Average
Max Hold
Min Hold
Multiplexer
Square Root
54
1 1
/ and / DIN
4 2
Up to 8 math blocks can be configured. Each block can be configured as one of 6 different
types (see Block Type below). The resulting analog value can be used as a source for other
function blocks, for example, Process Variable in the Custom Config parameter – see page
25.
The math block number (1 to 8).
Selects the type of math block required.
(See page 55 for Equation setup.)
Enables an equation with up to 4 operands and 3 operators to be created. The operands
can be assigned to any analog or digital signal (see page 79). Digital signals have a value of
either '0' or '1'. With the exception of the Median operator, the equation is processed in a
strict left to right order, with no operator precedence.
The result of a math block can be used as the operand in another math block, enabling more
complex math equations to be constructed. The math blocks are processed in ascending
order; Math block 1 is processed first, then Math Block 2, then 3 to 8.
Operator 1
Operand 1
Add, Subtract
Multiply, Divide
Operand 2
Low Select
High Select
Operand 3
Operand 4
(See page 55 for Real Time Average setup.)
Calculates the average value of a parameter over a user-configurable duration. The output of
the math block is updated at the end of the set duration only. A reset signal can be
configured to restart the calculation of the average value.
The average value is stored in case of power failure. If the duration of the power failure is
longer than the Average Duration (see page 55), the math block output value is set to zero.
(See page 55 for Max Hold / Min Hold setup.)
The math block output represents the highest / lowest value of the signal since it was reset.
(See page 56 for Multiplexer setup.)
Enables 1 of 2 analog signals or constant values to be selected using a digital signal.
A
B
Select
(See page 56 for Square Root setup.)
Calculates the square root of the selected sources value. If the input is less than 0, the
output is set to zero and the math block output state set to invalid.
Operator 2
Add, Subtract
Multiply, Divide
Low Select
High Select
Select
O/P
O/P
7 Advanced Level
Operator 3
Add, Subtract
Multiply, Divide
Low Select
High Select
IM/CM/ED–EN Rev. B