Process Dual Sensor Analog Input (PAID)

The Process Dual Sensor Analog Input (PAID) instruction monitors one analog Process Variable (PV) by using two analog input signals, from sources such as dual sensors, dual transmitters, and dual input channels. The PAID instruction monitors conditions of the channels and reports configured PV quality. The PAID instruction has functions for input selection, averaging, and failure detection. Additional functions, such as for filtering and alarming, are done by a downstream PAI block.

The PAID Instruction provides:

Available Languages

Ladder Diagram

Function Block Diagram

Structured Text

PAID (PAIDTag, 0);

Configuration Operands

P_ANALOG_INPUT_DUAL Structure

Public members are standard, visible tag members that are programmatically accessible. Private, hidden members are used in HMI faceplates and are not programmatically accessible. Private members are listed in separate tables after public members.

BUS_OBJ Structure

Operation

This diagram illustrates the functionality of the PAID instruction:

Alarms

Discrete tag-based alarms are defined for these members.

Mark the alarm as used or unused and set standard configuration members of the discrete tag-based alarm. Access alarm elements using this format:

PAIDTag.@Alarms.AlarmName.AlarmElement

There are Program, Operator, and External commands that enable the Reset and Reset & Acknowledge of all alarms of the instruction (Alarm Set) at the same time. This diagram shows how the commands interact with the PDO instruction.

Initialization

The instruction is normally initialized in the instruction first run. Request re-initialization by setting Inp_InitializeReq = 1. For proper initialization, when adding the instruction while performing an online edit of the code, make sure that Inp_InitializeReq = 1, the default value.

Configuration of Strings for HMI

Configure strings for HMI faceplates, as seen in FactoryTalk View, and for the Logix Designer configuration dialog box.

Monitor the PAID Instruction

Use the operator faceplate from the PlantPAx library of Process objects for monitoring.

Affects Math Status Flags

No.

Major/Minor Faults

None specific to this instruction. See Index Through Arrays for array-indexing faults.

Execution

Ladder Diagram

Function Block Diagram

Structured Text

In Structured Text, EnableIn is always true during normal scan. The instruction executes when it is in the control path activated by the logic.

Example

This example uses the PAID instruction to monitor one analog Process Variable (PV) using two analog input signals (dual sensors, dual transmitters). The PAID instruction allows you to select one sensor, the other sensor, or the average, minimum or maximum of either sensors. If difference between the two input signals exceeds a configured limit, an Alarm is generated.

In this example, an application uses two analog sensors (A, B). The average of these analogs is used elsewhere in logic to control a separate application element.

The Inp_PVAData and Inp_PVBData parameters are connected to the values from the two analog transmitters. The fault status of each of these sensors is tied to the bad input of the instruction (for example, Inp_PVABad). The output parameters Val, Sts_PVBad and Sts_PVUncertain, can then be connected to the Inp_PVData, Inp_PVUncertain and Inp_ChanFault for control.

Ladder Diagram

Function Block Diagram

Structured Text

PAI(AIT_201A);

PAI(AIT_201B);

AY_201.Inp_PVAData := AIT_201A.Val;

AY_201.Inp_PVASrcQ := AIT_201A.SrcQ;

AY_201.Inp_PVANotify := AIT_201A.Sts_eNotify;

AY_201.Inp_PVBData := AIT_201B.Val;

AY_201.Inp_PVBSrcQ := AIT_201B.SrcQ;

AY_201.Inp_PVBNotify := AIT_201B.Sts_eNotify;

PAID(AY_201,0);

AI_201.Inp_PVData := AY_201.Val;

AI_201.Inp_ChanFault := AY_201.Sts_PVBad;

AI_201.Inp_PVUncertain := AY_201.Sts_PVUncertain;

PAI(AI_201);