> ## Documentation Index
> Fetch the complete documentation index at: https://docs.siftstack.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Investigate a telemetry anomaly

> Isolate unusual signal behavior, compare related Channels, and identify the root cause of an anomaly.

After completing this topic, you can narrow down the root cause of an anomaly by isolating the affected time range and comparing related signals.

## Before you begin

* You have a Run with an identified anomaly open in [Explore](/documentation/reference/explore-settings) with the affected Channel plotted.

## How anomaly investigation works

When a signal shows unexpected behavior, you can zoom into the affected time range and plot related Channels side by side to determine whether the anomaly is isolated to a single signal or correlated across multiple signals.

Comparing related Channels helps narrow down the root cause, such as a sensor failure, an environmental event, or a system-level issue.

## Investigate an anomaly

1. In the toolbar, select a [range control](/documentation/reference/explore-settings#range-controls) to zoom into the time range where the anomaly occurs.
   * Range controls are available in Timeseries, FFT, and Scatter Plot Panels.
2. Add related Channels to the same Panel or [split](/documentation/reference/explore-settings#layout) the Panel by right-clicking its tab and selecting a split direction to compare signals in an adjacent Panel.
3. Optional: Create a [Calculated Channel](/documentation/reference/explore-settings#calculated-channels) to derive a signal that highlights the anomaly, such as a difference or ratio between two Channels:
   1. Click the <Icon icon="wave-pulse" /><Icon icon="plus-minus" /> **Calculated Channels** tab.
   2. Click <Icon icon="plus" /> **Create new Calculated Channel**.
   3. Select the **Asset** to attribute the Calculated Channel.
   4. In the **Calculated Channel name** box, enter a name.
   5. Click the **Input Channels** list.
   6. In the **Expression** box, enter the CEL expression.
      * To learn more, see [Expression syntax](/documentation/reference/expression-syntax).
   7. Optional: In the **Unit** box, enter a unit.
   8. Optional: Turn on the **Save to Asset** toggle to save the Calculated Channel for future reuse.
   9. Click **Add Calculated Channel**.
4. Optional: Add an [Annotation](/documentation/reference/explore-settings#annotations) to mark the anomaly for review or to share with your team:
   * In the <Icon icon="note-sticky" /> **Annotations** tab, click <Icon icon="plus" /> **Create new Annotation**, select a type (**Phase** or **Data Review**), configure the fields, and click **Add Annotation**.
   * Alternatively, click <Icon icon="square-dashed-circle-plus" /> **Select X**, drag over the time range in the Timeseries Panel, right-click the selection, and select <Icon icon="plus" /> **Create Annotation**.
5. Optional: In **Explore**, click <Icon icon="link" /> [**Share**](/documentation/reference/explore-settings#share) to send the exact state of your investigation to another engineer.
6. Optional: Create a [Rule](/documentation/review/detect-deviations-automatically-using-rules) to automatically detect the same anomaly in future Runs.

## Reference

* [Explore settings](/documentation/reference/explore-settings)