Mbars improperly displayed as bars

Grafana Time Series Panel
1

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  • What Grafana version and what operating system are you using?

Docker grafana/grafana-enterprise:latest@sha256:8861608c3eec1a888ce92a528956f0a93cffdd7f66ceff2a9bd2787c99a3d7c8 / Grafana v9.4.3 (cf0a135595)

OpenMediaVault 6.3.5-2

Also able to reproduce the bug on https://play.grafana.org/ (i.e. take 1 - Time series graph, set the unit to millibars, and use the transformations below to get it close to the range that weather data is typically in).

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  • What are you trying to achieve?

Display weather station pressure data

  • How are you trying to achieve it?

Using a time series panel in grafana

  • What happened?

Grafana applied automatic SI unit scaling to convert mbar into bar, but this is unexpected and unwanted for this use case. Station pressure data is always provided as mbar, even when above 1000 mbar.

  • What did you expect to happen?

Grafana uses mbar in the yaxis values and in the tooltip when hovering over datapoints.

  • Can you copy/paste the configuration(s) that you are having problems with?
  • Did you receive any errors in the Grafana UI or in related logs? If so, please tell us exactly what they were.

This bug appears as incorrect behavior, there are no errors or logs associated.

  • Did you follow any online instructions? If so, what is the URL?

N/A

2

I would say that automatic SI unit conversion is correct. Grafana is doing that to have nice, short, human friendly numbers in graphs.

I would try to define custom unit mbar, instead of predefined mbar unit. I guess Grafana won’t be doing automatic SI conversation then.