VariableMonitorActivity

Category: Common Steps Namespace: CMS.Plugin.FlowManagement.Domain.FlowBusiness.Activitys Base Class: BusinessActivity Module: FlowManagement.Domain

Overview

VariableMonitorActivity (Variable Monitor) is a node used to listen for changes in external variables in the process. It inherits from BusinessActivity and triggers subsequent process execution when the monitored variable value meets the condition, commonly used in PLC signal trigger scenarios.

Configuration Description

Property Name	Type	Required	Default	Description
MonitorMode	MonitorMode	Yes	ValueCompare	Monitor Mode (ValueCompare/ValueChange)
MonitorVariableName	string	Yes	-	Monitored Variable Name
CompareVariableValue	string	No	-	Comparison Value
NOT	bool	No	false	Invert Result
CompareOldValue	bool	No	false	Whether to compare old value
NeedTagChange	bool?	No	-	Whether tag change is needed
WaitTimeout	int	No	-1	Wait Timeout (milliseconds), -1 means infinite wait
UnsubscribeOnExit	bool	No	true	Unsubscribe on exit
ReadRetryCount	int	No	3	Read retry count
ReadRetryDelay	int	No	500	Read retry delay (milliseconds)

Usage Examples

{
  "Type": "VariableMonitorActivity",
  "Name": "Wait Start Signal",
  "Alias": "WaitStartSignal",
  "MonitorMode": "ValueCompare",
  "MonitorVariableName": "DB1.StartSignal",
  "CompareVariableValue": "1",
  "NOT": false,
  "WaitTimeout": -1
}

Notes

• 💡 Supports two monitor modes: value comparison and value change.
• 💡 CompareVariableValue="IsNullOrWhiteSpace" indicates monitoring for empty values.
• 💡 Exit mode is Manual.
• ⚠️ Requires variable service configuration to support subscription function.

Related Nodes

• VariableReadActivity: Read Variable Node
• VariableWriteActivity: Write Variable Node

Update History

Date	Version	Description
2025-11-28	1.0	Initial version

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Last updated: 2025-11-28