Historian Tags (Reference)

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Configuration Properties

Creating Historian Tags

Prerequisites

• Configured HistorianTable (or use default Table1)
• Tags defined in Unified Namespace
• Understanding of collection requirements

Configuration Steps

1. Navigate to Historian → Historian Tags
2. Enter TagName or select from list
3. Configure deadband parameters:
   • DeadBand for value changes
   • Deviation for time overrides
   • RateOfChange for velocity triggers
4. Select DeviationDeadBandType
5. Choose target HistorianTable

Deadband Configuration

DeadBand (Value Change)

Minimum absolute change required for storage:

• Applied with SaveOnChange trigger
• Reduces database writes
• Filters noise and minor fluctuations

Example:

TagName: Tank.Level
DeadBand: 0.5
// Only stores when level changes by ±0.5 units

Deviation (Time Override)

Overrides TimeDeadBand interval when exceeded:

• Forces storage regardless of time interval
• Captures significant changes immediately
• Works with TimeDeadBand configuration

Example:

TagName: Reactor.Temperature  
Deviation: 5.0
TimeDeadBand: 60 seconds
// Stores every 60s OR when temp changes by ±5°

RateOfChange (Velocity)

Triggers on rapid value changes:

• Measured in units per second
• Detects process upsets
• Overrides time intervals

Example:

TagName: Pressure.Line1
RateOfChange: 10
// Stores when pressure changes >10 PSI/second

DeviationDeadBandType

Absolute

Fixed unit threshold:

Current Value: 100
Deviation: 5
Triggers at: <95 or >105

Percentual

Percentage of current value:

Current Value: 100
Deviation: 5 (%)
Triggers at: <95 or >105

Current Value: 200
Deviation: 5 (%)
Triggers at: <190 or >210

UserType Tags (Template Tags)

Archive entire templates or specific properties:

Full Template

TagName: Pump1
// Archives all properties of Pump1 template

Specific Property

TagName: Pump1.Motor.Current
// Archives only motor current property

Multiple Instances

When using template arrays:

TagName: Pumps[1].Flow
TagName: Pumps[2].Flow
// Individual configuration per instance

HistorianTable Assignment

Grouping Strategy

Assign tags to tables based on:

• Update frequency
• Process relationships
• Data types
• Storage requirements

Best Practices

Runtime Behavior

SaveOnChange Mode

Tag changes → Check DeadBand → Store if exceeded

Trigger Mode

Trigger fires → Store all table tags → Apply timestamp

TimeDeadBand Mode

Timer expires → Check Deviation/RateOfChange → Store if exceeded OR timer

Performance Optimization

DeadBand Settings

• Analog signals: 0.1-1% of range
• Digital signals: Usually 0 (all changes)
• Calculated values: Based on significance

Table Organization

• Group similar update rates
• Separate critical from non-critical
• Consider query patterns
• Balance table sizes

Storage Efficiency

• Use Normalized tables for sparse data
• Standard tables for synchronized data
• Enable compression where supported

Common Configurations

Temperature Monitoring

TagName: Furnace.Temperature
DeadBand: 0.5
Deviation: 10
RateOfChange: 5
DeviationDeadBandType: Absolute
HistorianTable: ProcessData

Level Tracking

TagName: Tank.Level
DeadBand: 0.1
Deviation: 5
DeviationDeadBandType: Percentual
HistorianTable: TankFarm

Discrete Events

TagName: Pump.Status
DeadBand: 0
HistorianTable: Events
// Captures all state changes

Troubleshooting

Data not archiving:

• Verify tag name spelling
• Check HistorianTable is active
• Review deadband settings
• Confirm tag has valid quality

Excessive storage:

• Increase deadband values
• Review deviation settings
• Check for oscillating tags
• Enable time deadband

Missing rapid changes:

• Decrease RateOfChange threshold
• Reduce deviation value
• Check scan rates
• Verify trigger configuration

Template tags not working:

• Confirm template structure
• Check property paths
• Verify array indices
• Review instance names

Best Practices

1. Set appropriate deadbands - Balance detail vs storage
2. Group related tags - Same table for correlated data
3. Document settings - Record why values chosen
4. Test configurations - Verify before production
5. Monitor performance - Track storage growth
6. Use templates efficiently - Archive needed properties only
7. Plan for maintenance - Consider future adjustments

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