The Virtual Connector provides items that can store and return values without connecting to external hardware, a database, or a cloud service. Use it as an intermediate data layer when you need to combine, format, calculate, test, or redistribute values between other Connectors.

This guide explains how to create a Virtual instance and its items, connect them with mappings, verify the result, and its various use cases.

Before you begin

Make sure that:

• The Virtual Connector is installed and enabled.
• The source and destination instances are configured if the virtual items will exchange data with other Connectors.
• You know whether each virtual item must receive values, provide values, or do both.
• You know whether the value must be transformed before it is stored or sent to another item.

Use cases

Format a value once and reuse it

Use a virtual item as a common processing point when the same source value must be sent to several destinations in the same format.

For example, map a machine value to a virtual item, apply the required formatting, and map the result to an MQTT Connector and a database Connector. This avoids maintaining equivalent formatting on several source mappings.

Combine several values into one payload

Use the virtual item's Input template (writings) to create a structured payload containing values from several items.

For example, create one JSON value containing a temperature, pressure, machine name, and timestamp. The completed payload can then be mapped to an MQTT topic, REST endpoint, file, or cloud Connector.

Use SIA Connect variables in the template to reference the required items. Any mapping that updates the virtual item can cause the template to be evaluated with the latest referenced values.

Calculate a derived value

Use Post-processing (readings) to convert or calculate a value without changing the original source item.

For example, a source item can provide a temperature in degrees Celsius. A virtual item can calculate the Fahrenheit value, which can then be logged or mapped to another system.

Write a processed value back to a controller

Use a virtual item between a measured value and a writable controller item when the value must be calculated before it is written.

For example, map a source value to a virtual item, apply a scaling expression, then map the processed value to a writable PLC item.

Important: Writing to a PLC or other control device can affect equipment operation. Verify the calculation, mapping direction, limits, and destination item before enabling the mapping.

Test a destination Connector

Use a virtual item as a controllable test source when a physical device is unavailable.

Write a known value to the virtual item, then map it to an MQTT broker, database, REST endpoint, file, or other destination. This lets you verify the destination configuration and payload format independently of the production source.

Separate data acquisition from delivery

Use a virtual item as an intermediate layer between a source Connector and one or more destination Connectors. This keeps source acquisition separate from destination-specific formatting and makes the data flow easier to change later.

Create a Virtual instance

1. Sign in to the Edge Portal.
2. Open Workspace > Instances.
3. Select Add instance.
4. Select the Virtual Connector.
5. Enter a descriptive instance name.
6. Optionally enter a description and adjust the common instance settings.
7. Select Create.

The Virtual Connector does not add any Connector-specific instance parameters. Settings such as the name, description, enabled state, and default read interval are standard SIA Connect instance settings.

Create a virtual item

1. Open the Virtual instance.
2. Open the Items section.
3. Select Add item.
4. Enter a unique item name.
5. Optionally add a description, unit, and tags.
6. Select the required Read write setting.
7. Configure the common item settings needed for the application.
8. Select Create.

The Virtual Connector does not add any Connector-specific item parameters. Configure the item by using the standard fields available to all items.

Advanced settings such as logging, triggers, data retention, and processing are handled by SIA Connect rather than by the Virtual Connector itself.

Connect the virtual item with mappings

A mapping determines where the virtual item receives its value and where that value is sent.

Receive a value from another item

1. Open the source instance or the Virtual instance.
2. Create a mapping from the source item to the virtual item.
3. Choose a one-way mapping when values should only flow into the virtual item.
4. Configure any required mapping condition, trigger, template, or store-and-forward behavior.
5. Save the mapping.

When the mapping writes to the virtual item, the Connector stores the incoming value for that item. Later reads return the current runtime value.

Send the value to another item

1. Create a mapping from the virtual item to the destination item.
2. Configure the mapping direction and trigger required by the destination.
3. Save the mapping.
4. Confirm that the destination receives the expected value.

You can map one virtual item to several destinations. This is useful when the same processed value or payload must be reused without repeating the same formatting on every source item.

Understand how values are stored

The Connector keeps a current runtime value for each virtual item after the item has been written. When the item is read:

• If a runtime value exists, the Connector returns that value.
• If no runtime value has been written since the Connector started, it requests the item's current value from the SIA Connect database.

This behavior allows the item to act as a simple value container. The standard item logging and retention settings determine how values are stored in the SIA Connect database.

Verify the configuration

1. Open the Virtual instance and locate the configured item.
2. Write a known test value directly or allow the source mapping to send one.
3. Confirm that the virtual item's current value changes.
4. If post-processing is configured, confirm that the displayed result is correct.
5. Confirm that each destination mapping receives the expected value or payload.
6. Review the item and mapping errors if any stage does not update.

Troubleshoot the Virtual Connector

The virtual item has no value

• Confirm that the item is enabled.
• Confirm that a value has been written directly or received through a mapping.
• Check that the source item has a current value.
• Confirm that the source-to-virtual mapping is enabled and its condition or trigger can run.

The value does not update

• Check the mapping direction and make sure the virtual item is the intended destination.
• Confirm that the virtual item's Read write setting permits incoming writes.
• Check the source item's read interval and timestamp.
• Review mapping conditions, triggers, and minimum intervals that can prevent an update.

The value changes but the destination does not update

• Confirm that the virtual-to-destination mapping is enabled.
• Make sure the destination item permits writes.
• Check the destination Connector and instance status.
• Review any mapping condition, trigger, template, or store-and-forward setting.

The formatted value is incorrect

• Review Input template (writings) and Post-processing (readings).
• Check that every referenced item has a current value.
• Confirm that numeric and text values use the expected format.
• Open the item details and check for an input-template or post-processing error.

Values from several sources overwrite each other

The Connector stores one current runtime value for each virtual item. The latest incoming write replaces the previous value. Create separate virtual items for independent values, or use an input template to build one combined payload.

The value after a Connector restart is unexpected

The in-memory runtime values are cleared when the Connector stops. Until a new write arrives, the Connector requests the current saved item value from the SIA Connect database. Send a new value and review the item's logging and retention configuration if the saved value is not the one you expect.

No Connector-specific parameters are shown

This is expected. The current Virtual Connector does not define custom instance fields, item fields, files, discovery settings, or network settings.

Related articles

• Install and manage Connectors
• Create and edit instances
• Create and edit items
• Create and edit mappings
• Troubleshoot Connectors, instance, item, and mapping errors