> For the complete documentation index, see [llms.txt](https://documentation.nomos-system.com/nomos-system/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://documentation.nomos-system.com/nomos-system/integrator-en/devices/data-log.md).

# Data Log

In the **"Data Log"** tab you can record numeric and logical values of a device over time and display them as a chart. This is useful for tracking the history of e.g. temperature, power consumption, or door status over days and weeks.

The tab is only shown if the device has at least one loggable property.

## Selecting a property

Use the dropdown at the top right to select the property whose history should be displayed (e.g. temperature, power, brightness).

* Properties that already have logging enabled are marked with a **●**.
* Properties without logging can also be selected here and enabled in the next step.

## Enabling logging

If logging is not yet active for the selected property, the **"Enable Logging"** button appears. After clicking, values are recorded from that moment on.

## Chart and settings

Once logging is active, the chart with all collected values is shown. Below the chart you find the following settings:

* **Color** – The color picker sets the color of the chart line. Changes are saved automatically.
* **Samplingrate** – Determines the interval at which values are recorded:
  * **All Data** – Every value change is recorded.
  * **5 seconds to 60 minutes** – Values are only recorded at this interval, which saves storage space.
  * For boolean properties (e.g. on/off), the sampling rate is fixed to **All Data**.

## Actions

The following buttons are available below the chart:

* **Reset Logging** – Deletes all recorded values, but keeps logging active.
* **Disable Logging** – Stops logging and deletes all recorded values.
* **Export as .csv** – Exports the values in CSV format for further processing (e.g. in Excel).
* **Export as .json** – Exports the values in JSON format for use in custom applications.

{% hint style="danger" %}
**Warning:** Both **"Reset Logging"** and **"Disable Logging"** permanently delete the collected data. A confirmation prompt is shown before the action.
{% endhint %}


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