Allen-Bradley ProcessLogix 1756-IA16, Reference Manual, Page: 49 / 120

Publication 1757-RM810A-EN-P - May 2002
Functional Blocks 3-9
Data Acquisition Block
DATAACQ
Description Processes a specified process input value (P1) with or without filtering into an output value (PV).
Function Normally configured to fetch process input from an AI device, controller or another function block; it performs the
following major functions:
•
Brings input data and updates the input (P1) and its status P1STS. If input provides value only, P1STS is derived
from the value.
•
PV characterization option lets you configure Linear or Square Root conversion on the P1 input, if required.
•
Low signal cut off function lets you configure a low cutoff value for P1 with Linear or Square Root PV
characterization.
•
Performs filtering (P1FILTTIME) and clamping (P1CLAMPOPT) on P1 through parameters P1FILTTIME and
P1CLAMPOPT, and stores the result in PVAUTO.
•
Generates alarm flags when PV exceeds any of a number of user-specified alarm trip points for more than a
designated time interval.
•
PV source selection option (PVSOURCE) supports automatic, manual, and substitute. A PV source selection of
manual means an operator can store a value to the output (PV). A selection of substitute means a user program can
store a value to PV.
Inputs
•
Requires one process input value (P1) that must be fetched from another block.
•
Number of process input connections (NUMPINT) is 1.
•
P1STS provides the status of P1.
Input Ranges
and Limits
•
PVEUHI and PVEULO define the full range of P1 in engineering units.
•
PVEUHI is 100% of full scale value.
•
PVEULO is 0% of full scale value.
•
PVEXHILM and PVEXLOLM define the high and low limits of P1in engineering units.
•
If P1 clamping is desired (P1CLAMPOPT = Enable), the block clamps the input within PVEXHILM and PVEXLOLM.
Output Produces an output value (PV) and its status (PVSTS).
Alarm
Processing Block may be configured to generate an alarm when PV exceeds one of various trip points (XXXX.TP parameters) for
more than a specified time.
Parameters with the following suffixes also apply to alarm processing:
•
XXXX.DB, XXXX.DBU (deadband, deadband units)
•
XXXX.FL (alarm flag)
•
XXXX.PR (priority)
•
XXXX.SV (severity)
•
XXXX.TP (trip point)
•
XXXX.CT (alarm count)
•
Where XXXX stands for one of the following:
PVHIALM PVLLALM PVHISIGCHG
PVHHALM ROCPOSALM PVLOSIGCHG
PVLOALM ROCNEGALM BADPVALM
Parameters on following page
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