UNS OpenHubDocumentation

Schema administration

Understand and create a measurement unit

A measurement unit is a reusable catalog entry used to describe values, such as °C or kWh. Use this guide when inspecting an existing entry or creating one; neither action converts existing data or changes the unit published by a live topic.

Applies to
Schema · Measurement unit · View, Edit, and New
Guide version
1.0

Worked example

Example: degrees Celsius

Use this when temperature values are interpreted and displayed in degrees Celsius.

Category temperature

Groups compatible units so administrators can find them together.

Key celsius

Stable identifier. Together with Category, it identifies this catalog entry.

Symbol °C

Short display token shown next to values.

Label Degrees Celsius

Optional readable name when the key or symbol needs clarification.

Description Temperature relative to the Celsius scale.

Canonical description for administrators and future translations.

Procedure

Follow the task in order

  1. 1
    Check the catalog firstReuse an existing unit when its category, key, and symbol already describe the same measurement.
  2. 2
    Choose a category and stable keyUse a category such as temperature, pressure, energy, or flow. The category and key together identify the unit.
  3. 3
    Add the display symbolUse the concise token that administrators expect beside values, for example °C, kWh, or bar.
  4. 4
    Explain unfamiliar unitsAdd a label and description whenever the symbol alone is ambiguous or the measurement has a domain-specific meaning.
  5. 5
    Use the unit from attribute definitionsAfter saving, select this unit as the preferred unit on compatible attribute types.

Expected result

What you should have

A reusable measurement-catalog entry. Attribute definitions can select it as their preferred unit; this action does not rescale existing values or rewrite publishers.

Boundaries

Important boundaries

  • Creating a catalog unit does not convert values from one scale to another.
  • Keep the symbol concise and keep the category/key stable once other attribute definitions rely on it.
  • Use a specific description when the same symbol can mean different measurements in different domains.

This versioned public guide is maintained with the UNS OpenHub website and linked directly from the controller where the task applies.