Plugins 〉Psychart

Nicolas Ventura

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  • Installation
  • Change log
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A Psychrometric Chart for Monitoring Data Center Health & Human Comfort

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View air conditions on a psychrometric chart.

What is a psychrometric chart?

Psychrometric charts are charts adopted by ASHRAE that plot various thermodynamic properties of air-vapor mixtures. These charts are particularly useful in HVAC applications. The following properties describe what's called a state of air. Two properties are needed to fix the state of air, which means that two properties are needed in order to calculate every other property. The following 4 properties are plotted by Psychart by default:

  • Dry Bulb
    • The temperature of air using a dry thermometer.
  • Wet Bulb
    • Wet bulb temperature can be practically explained by the temperature of a surface where water is evaporating.
  • Dew Point
    • Water will condense from the air at or below this temperature.
  • Relative Humidity
    • A ratio of vapor pressure in the air to the saturation vapor pressure. 0%rh indicates absolutely dry air, and 100%rh indicates saturated air.

Psychart also has the capability to derive the following state variables, which are optionally displayed using the Show Advanced State Variables switch in Display options.

  • Vapor Pressure
    • The partial pressure of water in the vapor-air mixture.
  • Humidity Ratio
    • Weight of water vapor per weight of dry air.
  • Enthalpy
    • In thermodynamics, refers to the total heat content of the vapor-air mixture.
  • Specific Volume
    • Amount of volume taken up by one unit of mass of the vapor-air mixture.

Getting started

This section will go over the options in the panel editor.

Panel options

This is the default panel options for all Grafana panels which gives the user access to the panel title and description and other UI effects.

Chart options

These options affect how the chart itself is displayed.

Allows the user to select whether measurements are being reported in US or SI units, the local altitude, graph bounds, and optionally display ASHRAE comfort regions (envelopes). For data center envelopes, these comfort regions follow the 2021 ASHRAE standard and are designed for data centers and IT spaces of various criticality. For human comfort envelopes, these comfort regions follow the ASHRAE-55 guidelines published in 2017. These human comfort envelopes are a function of metabolic rate (MET, which is dependent on the indoor activity), clothing level (CLO), and air speed. In both cases, the envelopes show the target region for conditioned air supplied into the indoor space.

Data options

These options help process the incoming data.

Psychart is capable of plotting 1 series of states per panel. Due to the fact that 2 properties are needed to fix the state, two numeric time-dependent fields are required. The user must select whether those two fields are dry bulb and wet bulb, dry bulb and dew point, or dry bulb and relative humidity. These fields must then be entered into the field selectors below respectively.

It is important to note that one or two queries may be necessary depending on the data structure. One single query may be sufficient to return the two fields needed to fix the state. Other times, one query will be needed to obtain the dry bulb field and another for relative humidity field, for example.

Display options

This section changes the visual appearance of data within the chart.

Allows the user to change the point radius, optionally draw a line between adjacent points in time, and select a color gradient for the data series. The user can also optionally select to view more state variables here.

Errors & Troubleshooting

Some errors can arise from the Data options section due to the fact that wet bulb and dew point must be less than or equal to the dry bulb temperature and relative humidity must be within the range of 0-1. If relative humidity is a driving measurement, make sure that the measurement type is correct (0-1 or 0%-100%). For other measurements, make sure that they are being reported correctly.

Psychart matches up values with similar timestamps. For a dry bulb & relative humidity series, the dry bulb measurement timestamp must match that of the relative humidity timestamp in order to be recognized as a single point. The Query options in the query inspector may provide the tools required to fix any time discrepancies.

Importantly, if there is missing data in one field, for example if dry bulb temperature has not been reporting for the last 5 minutes, no new states are calculated, and no new data is plotted in Psychart for the last 5 minutes to avoid the display of inaccurate data.

Psychart works best both visually and practically when observing a narrow span of time. If Psychart is loading very slowly, try to decrease the Time range in Grafana. Both absolute and relative time spans are accepted by Psychart. If the data still seems too cluttered, try disabling the line that connects the series or reducing the point radius.

Finally, if there are issues after upgrading to a newer version of Psychart, (for example the regions are not being rendered) try to open the panel editor, reapply your customization settings, and save the panel. Sometimes, the panel options are not properly stored from version to version.


Psychart was created by Nicolas Ventura and is distributed under a modified BSD License. Plugin ID: ventura-psychrometric-panel

Copyright Notice


HVAC use case: Air handler supply temperatures. There are many different styling options for Psychart. Psychart can render data in imperial or metric units! IT use case: Data center supply air conditions. Hover the mouse over the shaded regions to learn more! Hover the mouse over the data points to show the thermodynamic properties of air. (Currently showing advanced state variables.) Meteorological use case: Long-term outdoor air conditions. General use case: Psychart as a thermodynamic calculator. Grafana configuration options for Psychart. Data options panel for Psychart. Display options panel for Psychart.

Installing Psychart on Grafana Cloud:

For more information, visit the docs on plugin installation.



  • Update to the latest version of @grafana/create-plugin (1.12.0)


  • Update to the latest version of @grafana/create-plugin (1.10.0)
  • Fix incorrect plugin ID in docker-compose.yaml
  • Remove references to GRAFANA_API_KEY in favor of GRAFANA_ACCESS_POLICY_TOKEN


  • Update to the latest version of @grafana/create-plugin (1.9.0)
  • Remove references to npm in build script
  • Store series value in label named field.config.displayNameFromDS


  • Update to the latest version of @grafana/create-plugin (1.6.3)
    • Grafana version required: >=9.5.3
  • Automatically build and validate plugin in validation script


  • Update to the latest version of @grafana/create-plugin (1.3.0)
  • Change yarn commands to npm run


  • Move from base folder to src/
  • Update dependencies


  • Screenshots are moved to


  • Screenshots are no longer packaged with the plugin
  • Add more and new screenshots with better descriptions
  • Fix bug that prevented the default gradient from being set
  • Don't attempt to plot data if no field names are selected
  • Show an error if field is not found or otherwise invalid
  • Show an error if maximum dew point > maximum dry bulb
  • Add author contact information in plugin.json
  • Publishing script now ensures changelog matches published version number


  • Set Viridis as the default color gradient
  • Add a short blurb in in Troubleshooting to explain how to fix errors when upgrading to major versions


  • Migrate from a JavaScript to a TypeScript code base
  • Dynamically generate region & gradient selections in both the standalone app and the Grafana plugin
    • This means, less code duplication, so it will be much easier to add additional regions or gradients in the future
  • Regions are now rendered in a blue gradient instead of a violet gradient
  • Tooltips now follow the mouse instead of being in predefined calculated positions
  • Regions, chart axes, and points are no longer rendered outside of chart boundaries
  • Rebuild with npx @grafana/create-plugin@1.0.0 to make sure source files and dependencies are up-to-date
  • Better support for long and multi-frame time series (wide time series still not implemented)
    • For now, if you are using a wide time series, use the Grafana transform to convert to the long or multi-frame format
  • Standalone app now adds timestamps to data points by default
  • Minor updates in to explain new ASHRAE guidelines and to update badges
  • Add link to official Grafana blog post in plugin.json
  • Add more relevant search keywords in plugin.json


  • Fixed broken badges in
  • Fixed link to copyright notice in
  • Removed references to plugin signing
  • Minor improvements to build pipeline


  • Use the new Grafana plugin builder from
    npx @grafana/create-plugin
  • Added additional workflows for compatibility and testing the build


Minor updates in packaging.

  • Fixed instances of incorrect package name.
  • Updated website URL
  • Added plugin download URL


First public release in Grafana. Click here to visit the plugin's page.

  • Updated badges
  • Updated screenshots
  • Other small fixes in README


Pre-release with a few minor non-code updates.

  • Small edits in README and CHANGELOG


Pre-release with data source bug fix.

  • Psychart can now detect if a data source calls each series by its frame name, field name, or a concatenation of both (for example, the Static Datasource)


Initial release with base features.

  • Visualization of one data series of psychrometric properties with various field options
  • A robust chart editor with graph options and display options
  • Interactivity via hovering over data points or parts of the graph with the mouse