BME688 gas sensor warmup etc.

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garberw
 
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BME688 gas sensor warmup etc.

Post by garberw »

See graphs; I have two BME688 and they totally do not agree. One is a few days old, the other months older.
I know there is a warmup time of about 48 hours but looking at weekly graph it should have been plugged in long enough but it is still going up and up.
I have to say right off that I cleaned the new enclosure (NOT THE BME688 !!!!) with acetone (a VOC volatile organic compound a gas it detects) but that was maybe a week ago. how could that still affect it?
I think the air quality inside here is okay so the older (wmod) is probably correct. Also the newer (atlas) is getting a few spikes in the temperature but not the humidity. It was suggested that the arduino it was hooked up to could have a bad usb connection or there could be some faulty soldering (solder was making balls on pins) or I left the soldering iron tip on the pin more than two seconds and it got damaged but it seems to be functioning. I replaced most of the usb cables so we will see soon if that fixes the spikes but it can not cause the crazy gas readings.
wmod_gas_iaq.png
wmod_gas_iaq.png (9.66 KiB) Viewed 74 times
atlas_gas_resis_weekly.png
atlas_gas_resis_weekly.png (9.64 KiB) Viewed 74 times
atlas_gas_resis_iaq.png
atlas_gas_resis_iaq.png (18.19 KiB) Viewed 74 times
I can't solder so great since I have bad tremor.

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garberw
 
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Re: BME688 gas sensor warmup etc.

Post by garberw »

wmod_gas_resis.png
wmod_gas_resis.png (11.37 KiB) Viewed 73 times
IAQ index of air quality is computed from gas_resistance by program
by David Bird
http://www.dsbird.org.uk

I might add that the BME688 appeared to be in older packaging. It was from adafruit. Could it be an older model? Using adafruit arduino C++ library.
regards

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garberw
 
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Re: BME688 gas sensor warmup etc.

Post by garberw »

spikes in temp not humidity.
spikes_in_temp.png
spikes_in_temp.png (17.6 KiB) Viewed 70 times
lower iaq is better and corresponds to higher gas resistance.

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garberw
 
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Re: BME688 gas sensor warmup etc.

Post by garberw »

atlas_iaq_sinking_open_window_fan.png
atlas_iaq_sinking_open_window_fan.png (10.07 KiB) Viewed 65 times
with an open window and a fan the weekly plot for the atlas (new one) shows iaq sinking in the last few hours.
At this rate it would take 3 more for a total of 6 days to reach the steady state of the older burned in one wmod.

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garberw
 
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Re: BME688 gas sensor warmup etc.

Post by garberw »

the end of the story is that the bme688 took two to three weeks for the gas to equilibrate or auto-calibrate or whatever. it ended up at about 300 kOhm and an iaq of about 20 (clear breathable air).

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