Filter
Top Products
Instruction Manual
IM-106-880C, OI
September 2009
Hazardous Area OCX 8800
7-56
This allows a ratio to be set up that increases the level indication at block
output for an increase in the tank temperature relative to ambient
temperature.
Figure 7-25. Arithmetric
Function Block Diagram
Example
This application can be applied to very large storage tanks whose contents
are subject to thermal expansion and contraction during seasonal changes in
temperature.
Advanced Topics Arithmetric Types
The parameter ARITH_TYPE determines how PV and the compensation
terms (t) are combined. User may select from nine (9) commonly used math
functions, depicted below. COMP_HI and COMP_LO are compensation
limits.
If there is a divide by zero and the numerator is positive, f is set to COMP_HI;
if the numerator is negative, then f is set to COMP_LO.
The square root of a negative value will equal the negative of the square root
of the absolute value. Imaginary roots are not supported.
If there is a divide by zero and numerator is positive, f will be limited to
COMP_HI; if the numerator is negative, f will be limited to COMP_LO.
Compensation inputs which are not usable are not included in the calculation.
PV is always included.
OUT
IN_1
ARTHM
Block
39930021
LIQUID_TEMP
IN
TANK_LEVEL
IN_2
AIR_TEMP
ARITH_TYPE = FLOW
COMP-LINEAR
Flow Compensation Linear
COMP_HI
f=
COMP_LO
t(1)
t(2)
Flow Compensation Square Root
COMP_HI
f=
COMP_LO
t(1) t(3)
t(2)
√
func = PV · f func = PV · f
39930022
Flow Compensation
Approximate
COMP_HI
f = t(1) t(2) t(3)
2
COMP_LO
COMP_HI
f = + t(3)
COMP_LO
t(1)
t(2)
func = PV · f func = PV · f
39930029
BTU Flow
COMP_HI
f = t(1) - t(2)
COMP_LO
func = PV · f
Traditional Multiply
and Divide