Owner's manual

FOUNDATION
TM
Fieldbus Blocks Manual
7-4
Block Execution The INT function block integrates a variable over time. The integrated
or accumulated value (OUT) is compared to pre-trip and trip limits.
When the limits are reached, discrete output signals are generated
(OUT_PTRIP and OUT_TRIP). You can choose one of six integrator
types that determine whether the integrated value increases from zero
or decreases from the trip value. The block has two inputs and can
integrate positive, negative, or net flow. This capability is useful to
calculate volume or mass variation in vessels, or as an optimization tool
for flow ratio control.
The transfer equation used in the Integrator function block is:
You can choose integration type options that define the integrate up,
integrate down, and reset characteristics of the block. When you select
the SP to 0 - auto reset or SP to 0 - demand reset integration type option:
For all other integration types:
Figure 7-2 illustrates the relationship between the SP, PRE_TRIP,
OUT_PTRIP, OUT_TRIP, and RESET_IN parameters in the Integrator
function block.
To specify the execution of the INT block, configure input flow and rate
time variables, integration type and carryover options, and trip and
pre-trip action.
Figure 7-2. Integrator Function Block
Timing Diagram
Current Integral
∆t
2
-----


x y OUT t 1–[]++()×=
Where
Dt: the elapsed time since the previous cycle (in seconds)
x: the converted IN_1 value (based on the options you configure)
y: the converted IN_2 value (based on the options you configure), or zero if you select not to
use a second input
OUT[t-1]: the value of OUT from the previous cycle
Integral Integral Current Integral+=
OUT SP Integral–=
OUT Integral=
IN_1
SP
PRE_TRIP
OUT_PTRIP
OUT_TRIP
RESET_IN
5 seconds
(or = scan rate if
scan rate > 5 seconds)
Time
FIELDBUS-FBUS_22A