80209C_MHW_850-1650-1850_01-2020_ENG_pag. 232
5.17. Math oforations
5.17.1. Math function blocks
The math oforations function processes (with Math Function
Blocks) the values of input variables to obtain values for
output variables.
Math function blocks are programmed with GF_eXpress
software.
Math function blocks are executed every 60 ms, in sequence
from MFB1 to MFB8. Therefore, the maximum delay between
the change of an input and the update of its output is 60 ms.
Math function blocks continue to be executed even in Soft-
ware OFF conditions.
There is a maximum of 8 function blocks, each of which can
handle up to 2 analogue variables and 2 digital variables in
input and 1 analogue variable and 1 digital variable as output.
Input variables (a, b) can refer to:
• analog inputs,
• setpoint,
• alarm thresholds,
• control powers,
• support coefficients settable from serial or user menu,
• variables MFB_OUT_01… MFB_OUT_08 from other
function blocks,
• LFB_OUT_1...LFB_OUT_32.
The input variables (c, d) refer to variables LFB_OUT_01…
LFB_OUT_32 from logic function blocks.
2 types of oforations on inputs variables a, b can be executed
on math function blocks:
• Type 1: MATH FUNCTION (a, b);
• Type 2: MATH FUNCTION (a) + LOGIC RESET
COMMAND (c).
• Type 3: UP/DOWN COUNTER with prescaler x1, x10,
x100, x1000 of the logical input (d) + reset logical input
(c) with threshold (UP) or preset (DOWN) analogue (a)
and digital output at end of count + analogue counter
output (b);
• Type 4: COMPARISON of (a, b) with digital output
The result of the Math Oforations function can act on:
• process variables,
• local setpoint,
• value of analog outputs.
• Reference for alarms AL1…AL4
5.17.2. Groups of variables
The controller offers many variables that can be used in input
for math oforations.
These include the following groups of homogeneous
variables:
Analog inputs
IN1 Main input
IN2 Auxiliary input
CURR1 input from current transformer CT1
CURR2 input from current transformer CT2
Process variables
PV.1 Process variable for PID.1
PV.2 Process variable for PID.2
Local setpoint
NOTE: When the SETP.x is managed as a Math Function
Block output, the parameter can no longer be changed
from the display or by serial connection.
SETP1 local setpoint for PID.1
SETP2 local setpoint for PID.2
Multiset setpoint
M.SET1.1 multiset setpoint 1 for PID.1
M.SET2.1 multiset setpoint 2 for PID.1
M.SET3.1 multiset setpoint 3 for PID.1
M.SET4.1 multiset setpoint 4 for PID.1
M.SET1.2 multiset setpoint 1 for PID.2
M.SET2.2 multiset setpoint 2 for PID.2
M.SET3.2 multiset setpoint 3 for PID.2
M.SET4.2 multiset setpoint 4 for PID.2
Alarm thresholds
ALRM1 alarm 1 threshold
ALRM2 alarm 2 threshold
ALRM3 alarm 3 threshold
ALRM4 alarm 4 threshold
Control powers
OUT.P1 for PID.1
OUT.P2 for PID.2
Analog outputs
OUT.C continuous output
OUT.A1 analog output 1
OUT.A2 analog output 2
Support coefficients (displayable and settable on User
menu)
M.C1 mathematical coefficient 1
(with setting of the decimal point position in
M.DECP1)
M.C2 mathematical coefficient 2
(with setting of the decimal point position in
M.DECP2)
M.C3 mathematical coefficient 3
(with setting of the decimal point position in
M.DECP3)
M.C4 mathematical coefficient 4
(with setting of the decimal point position in
M.DECP4)
M.C5 mathematical coefficient 5
(with setting of the decimal point position in
M.DECP5)
M.C6 mathematical coefficient 6
(with setting of the decimal point position in
M.DECP6)
M.C7 mathematical coefficient 7
(with setting of the decimal point position in
M.DECP7)
M.C8 mathematical coefficient 8
(with setting of the decimal point position in
M.DECP1)
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