Same kind of sensors give different graph scale?

Tags: #<Tag:0x00007f328af79fb8>

Hi,

Can someone explain to me how it comes that two sensor devices of the same kind (TVOC + eCO2) come up with two totally different Graph Y-axis scale?
I played around with two kinds of TVOC + eCO2 sensors (CCS811 vs SGP30)
But as you can see is the graph of the CCS811 kinda useless.
image
The y-axis of the CCS811 sensor shows by default the value up to 8000 and doesn’t change.
The y-axis of the SGP-30 sensor shows a much more practical scal (and if i’m not mistaken it adjusts itself)

I try to understand how.

Both sensors are connected to a D1-Mini (one normal and one lite) and i use them with ESPHome.
The templates i use for both are:

CCS811

sensor:
  - platform: ccs811
    eco2:
      name: "CCS811 eCO2"
      accuracy_decimals: 1
    tvoc:
      name: "CCS811 TVOC"
      accuracy_decimals: 1
    address: 0x5A
    update_interval: 20s

SGP30

sensor:
  - platform: sgp30
    eco2:
      name: "SGP30 eCO2"
      accuracy_decimals: 1
    tvoc:
      name: "SGP30 TVOC"
      accuracy_decimals: 1
    address: 0x58
    update_interval: 20s

I hope that there is a way to align them better.

You have a single errant data point in the CCS sensor history (both TVOC and eC02):

17e6cf42976b72f12fa599604e0201c18e0a69cd

After 24 hours that will fall off the graph timescale and the Y axis will autoscale again.

Very good call.

image
indeed.

Really don’t know where that came from. (probably a startup glitch)
I’ve changed the “hours to show” to 4 hours and it is gone indeed.
image

Thank you for clearing that out.

Now i can focus on why the CCS811 sensor measures about 10x the TVOC value of the SGP30 sensor and around 3x the eCO2 value (same location…). :smile:
See the 3 hour period :face_with_monocle:
image

Yeah, that I don’t know.

It looks like calibration.

The SGP30 needs 12 hours to calibrate. The CCS811 just 20 minutes.
They are getting closer now.

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