---
title: XMR Chart
slug: litmusedge/xmr-chart
docTags: 
createdAt: 2024-08-06T18:54:17.057Z
---

The XMR Chart processor establishes a central line from a window of process data, then tracks the process against upper and lower control limits calculated from that line.

## Why use XMR Chart

Use this processor to monitor a process for control-chart-style drift once a baseline has stabilized, for example, tracking a machine's baseline vibration level and flagging when it moves outside its expected range.

## How it works

Once the window fills with values, the processor calculates a central line that stays constant going forward, along with:

- **Moving ranges**: the difference between successive values.
- **Average moving range**: the average of the moving ranges.
- **Upper and Lower Natural Process Limits**: the central line, plus or minus the product of **Process Limit Multiplier** and the average moving range.

The processor adjusts the central line if the current value falls outside the process limits multiple times in a row, or if multiple values in a row sit closer to either limit than to the central line.

If your input tag doesn't publish at a steady rate, use **Timer Interval** to publish a value on a fixed schedule instead of waiting for the next incoming event. Enter `0` to disable the timer if your input already publishes at the expected rate.

## Parameters

| **Parameter**            | **Details**                                                                                                                                    |
| ------------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------- |
| Window Size              | The window (in seconds) over which the central line and other calculated fields are established.                                               |
| Process Limit Multiplier | The factor used to calculate the upper and lower process limits. Influences the range within which the process is considered to be in control. |
| Timer Interval           | Sets a timer (in milliseconds) that continuously publishes the output when no event triggers a calculation. Enter `0` to disable the timer.    |

## Related topics

- [Use the XMR Chart Function](docId\:mYhAhjGKuSa9bWNGWVRJ0)