ABB 2600T Series Instruction Manual page 113

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Net Flow
To discern between forward and reverse flows, the Integrator block considers a negative sign as an indication of reverse flow.
Some flowmeters already indicate forward and reverse flows by adding a sign to the measurement value. Others use a separate
binary signal. This signal can be connected to the inputs REV_FLOW1 and REV_FLOW2, where True should invert the signal of the
corresponding input.
The net flow is obtained by adding the two increments. The net increment should have a positive or negative signal to indicate the
net flow direction. In order to integrate the difference between the inflow and outflow of a tank, for example, the second one can
be assigned to be negative.
The net flow direction to be considered in the totalization is defined in INTEG_OPTS. The following options are available:
FORWARD = only positive flows (after application of REV_FLOWi ) are totalized. The negative values should be treated as zero.
FORWARD is selected when the bit corresponding to Forward is set to true.
REVERSE = only negative flows are totalized. The positive values should be treated as zero. The option bit Reverse should be set to
true TOTAL = both positive and negative values should be totalized. Both option bits Forward and Reverse should
be set to true or to false.
Integration of Inputs:
There are three internal registers used for the totalization:
Total = The net increment is added every cycle, regardless of status.
Atotal = The absolute value of the net increment is added every cycle, regardless of status.
Rtotal = The absolute value of the net increments with bad status (rejects) are added to this register.
These internal registers may have greater precision than the standard floating point value. The value of Rtotal requires the same
precision as Atotal in order to be able to accumulate floating point fractions so that they are not lost as arithmetic underflow. The
value of a register that corresponds to standard floating point is called the most significant part of the register.
The most significant part of Total can be read in the output OUT, and of Rtotal in RTOTAL. OUT_RANGE is used only for display of
the totals by a host. The high and low range values of OUT_RANGE have no effect on the block.
Types of integration:
The value of OUT can start from zero and go up or it can start from a Setpoint value (TOTAL_SP) and go down.
Reset may be automatic, periodic, or on demand. This is defined by the enumerated parameter INTEG_TYPE:
1 UP_AUTO Counts up with automatic reset when TOTAL_SP is reached
2 UP_DEM Counts up with demand reset
3 DN_AUTO Counts down with automatic reset when zero is reached
4 DN_DEM Counts down with demand reset
5 PERIODIC Counts up and is reset periodically according to CLOCK_PER
6 DEMAND Counts up and is reset on demand
7 PER&DEM Counts up and is reset periodically or on demand
The first four types indicate use as a batch totalizer with a setpoint TOTAL_SP. This is not the standard SP because it does not have
the structure of SP that is defined in FF-890. The count does not stop at TOTAL_SP going up or zero going down, as it is important
to get the true total of flow. Two outputs, OUT_TRIP and OUT_PTRIP, are associated with the four types.
See Batch totalizer outputs below .
The next three types indicate that TOTAL_SP and the trip outputs are not used. The Periodic type (5) disables operator reset.
The internal registers always add the net increments. Counting down is done by setting OUT to the value of TOTAL_SP minus the
most significant part of Total.