UOM lost on restart & missing UOM definition at data collection level

Description

When using the ModbusTCP adapter (seems other Adapters impacted):

• Data is ingested into CDS as a stream

• A Unit of Measure (UOM) can be manually assigned to the stream in CDS or EDS.

• But on adapter restart, the UOM is automatically removed

This behavior is reproducible, has no workaround, and should be considered a bug. Adapter restarts should not remove user-defined metadata.

Requested Improvements

1. Bug fix

   • UOM assigned to a CDS stream must not be removed when the adapter restarts.

2. Functional enhancement

   • Allow defining the UOM directly at Data Selection level, e.g. via a unitOfMeasureId parameter alongside conversionFactor and conversionOffset.

{
"registerOffset": 4000,
"dataTypeCode": 20,
"conversionFactor": 10,
"conversionOffset": 0,
"unitOfMeasureId": "degree Celsius"
}

Functional Rationale

From an engineering and operational standpoint, this approach is more consistent and intuitive:

• The engineer defining the Modbus register mapping:

  • Knows the physical meaning of the data

  • Already defines conversionFactor and conversionOffset

• The unit is an integral part of the signal definition, just like scaling and offset

Defining the UOM as close as possible to the data source ensures:

• Clear expectations on the adapter output

• Better data quality and consistency in CDS

• Reduced risk of human error and post-processing corrections