National Instruments BridgeVIEW User Manual download pdf (Page 82)

Chapter 3 Tag Configuration

BridgeVIEW User Manual 3-24 © National Instruments Corporation

What Is Deadband?

In process instrumentation, deadband is the range through which an input

signal can vary without initiating an observable change in output signal.

Deadband usually is expressed in percent of full scale. Although the term

deadband generally applies only to analog tags, other tag types have a

limited type of deadband. A checkbox allows you to determine if updates

to the RTDB and historical data files should occur with any new data from

the device server or if the value has changed.

Note

The BridgeVIEW Engine performs historical logging and alarm management

operations based on new values in the RTDB. If you set the Update Deadband too

high, the RTDB might not be updated. This might result in inadequate historical

logging or alarm management.

How Do You Use Deadband to

IncreaseEngineThroughput?

The BridgeVIEW Engine uses Update Deadband and Log Deadband

values to eliminate unnecessary processing on minor data value changes.

Deadband allows you to define a significant change. The Engine ignores an

operation if the change in data is not considered significant. Deadband is

expressed as percent of full scale. For example, if the tag engineering range

is 0 to 200 liters, a deadband of 5% is 10liters. In addition, through I/O

group configuration, you can configure a server to apply a deadband to any

items associated with that I/O group. Not all servers implement deadbands.

OPC servers support deadbands.

Set Initial

Value

all Determines whether an initial value is used for this tag. If Set

Initial Value is OFF for this tag, the tag value is marked as

uninitialized until its value is updated.

Initial Value all The initial value used for this tag when Set Initial Value is ON.

Ifthe tag is an Output only or Input/Output tag, the BridgeVIEW

Engine sends the Initial Value to the server at Engine startup.

Ifthe tag is an Input only or Memory tag, the Initial Value is

stored in the RTDB at startup.

Table 3-4.

Operations Configuration Attributes (Continued)

Attribute

Applies to

Data Types

Description

1 2 ... 77 78 79 80 81 82 83 84 85 86 87 ... 454 455

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National Instruments BridgeVIEW User Manual Page 82