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Average Temperature Across Related Devices

Use a Related Entities Aggregation calculated field to collect temperature readings from multiple sensors and store the average on a parent asset.

Use case

Section titled “Use case”

Warehouse A contains two thermometer sensors. Each reports a temperature telemetry key.

ThingsBoard:

  • finds all devices related to Warehouse A via Contains relations
  • averages the latest temperature reading from each sensor
  • stores the result as avgTemperature on Warehouse A

Step 1. Create devices and asset

Section titled “Step 1. Create devices and asset”

Create an asset to represent the warehouse:

  • Name: Warehouse A
  • Asset profile: warehouse

Create two devices with the thermometer device profile:

  • Name: Sensor A1
  • Name: Sensor A2

Step 2. Create relations

Section titled “Step 2. Create relations”

Link both sensors to the warehouse using outbound Contains relations:

  1. Open Warehouse A details.
  2. Go to the Relations tab.
  3. Add an outbound Contains relation to Sensor A1.
  4. Add an outbound Contains relation to Sensor A2.

Step 3. Create calculated field

Section titled “Step 3. Create calculated field”

You can import a ready-made calculated field or build it manually.

Option 1. Import calculated field

  • Download the Warehouse Average Temperature calculated field as JSON file and import it into your instance.

Option 2. Create manually

  • Navigate to Calculated fields and click + Add calculated field.

General settings

Section titled “General settings”
  • Title: Warehouse Average Temperature
  • Entity type: Asset
  • Entity: Warehouse A
  • Type: Related entities aggregation
  • Aggregation path:
    • Relation direction: Down to child
    • Relation type: Contains

Argument

Section titled “Argument”

Click Add argument and configure it to read temperature from each related device:

  • Argument type: Latest telemetry
  • Time series key: temperature
  • Argument name: temperature
  • Default value: 0

Metric

Section titled “Metric”

Click Add metric and configure the aggregation:

  • Metric name: avgTemperature
  • Aggregation: Average
  • Value source: Key
  • Argument name: temperature

Output

Section titled “Output”
  • Output type: Time series
  • Decimals: 1
  • Strategy: Process right away

Click Add to save.

Step 4. Verify the result

Section titled “Step 4. Verify the result”

Post temperature telemetry to each device. Replace $ACCESS_TOKEN with the device access token.

Sensor A1:

Terminal window
curl -v -X POST -d '{"temperature": 21.06}' https://eu.thingsboard.cloud/api/v1/$ACCESS_TOKEN/telemetry --header "Content-Type:application/json"

Sensor A2:

Terminal window
curl -v -X POST -d '{"temperature": 23.84}' https://eu.thingsboard.cloud/api/v1/$ACCESS_TOKEN/telemetry --header "Content-Type:application/json"

The computed field reads the latest value from each related device, calculates the average, and stores it as the totalWaterConsumption time-series key for Warehouse A.

Expected result: Open Warehouse A ⇾ Latest telemetry tab. The avgTemperature value is 22.5 (average of 21.06 and 23.84, rounded to 1 decimal), updated automatically whenever new data arrives from either sensor.

See also

Section titled “See also”
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