Honeywell HC900 - Page 35

Design and Implementation of HC900 Control System - Allowable Function Blocks for Process and Safety Functions
Revision 1.9 HC900 Process & Safety Controller Safety Manual 27
01/14
DIV
Divides one input (X) by another (Y). If Y = 0, then
OUT = 0 and block status is set to error; otherwise,
OUT = X ÷ Y.
X
X
4 Input ADD
Adds four inputs (X, Y1, Y2, and Y3) to get an output.
X
X
4 Input SUB
Subtracts three analog inputs (X1, X2, X3) from input
Y to get an output.
X
X
4 Input MUL
Multiplies four inputs to get an output. Note: All four
inputs must be connected. Unconnected inputs
default to zero. If only 3 inputs are needed, the 4th
should be connected to a constant value of 1.
X
X
Free Form Math
Read inputs A through H and calculates the output
based on specified general purpose calculation.
X
X
Calculation
Blocks
Compare
Compares value of X input to value of Y input and
turns ON one of three outputs based on this
comparison.
X
X
Deviation
Compare
Compares up to 6 analog inputs to a + or - user-
entered deviation setpoint to a 7th input reference
value and sets the output true if any input exceeds
the deviation value from the reference value. Output
is off if all inputs are less than the deviation. Plus Dev
Compare Value = Reference input + User entered
Plus Deviation value. Minus Dev Compare Value =
Reference input - User entered Minus Deviation value
(Minus Deviation value should be a positive number).
If any IN (1-6) > the Plus Dev Compare value, Out =
ON. If any IN (1-6) < the Minus Dev Compare value,
Out = ON. Note: When the reference input is the
average of the 6 inputs, the block performs deviation
from average. Note: All inputs should be used or a
single value should be connected to multiple inputs.
Unused inputs will default to 0.
X
X
Absolute Value
Calculates the absolute value of a single analog
variable input. Useful when you need to output a
positive number.
X
X
Square root
Extracts the square root of the analog input (X) as
long as the input is greater than the configured
DROPOFF value. If X > DROPOFF, then: OUT =
square root of X. Otherwise, OUT = 0.
X
X
Mass Flow
Calculates gas mass flow (OUT) from differential
pressure input value (X) that represents a pressure
drop across an orifice plate (for example). It accepts
two other inputs to include pressure (Y) and/or
temperature (Z) compensation in the calculation. The
calculation includes square root extraction.
X
X