BME 280 wrong temp value

Moderators: grovkillen, Stuntteam, TD-er

Post Reply
Message
Author
Trainer
Normal user
Posts: 23
Joined: 03 Apr 2020, 15:45

BME 280 wrong temp value

#1 Post by Trainer » 04 May 2022, 19:28

Hello,

i got wrong temp values from my BME280.
the temperature difference is +2°C.

How can i get more accurate data?

User avatar
Ath
Normal user
Posts: 3416
Joined: 10 Jun 2018, 12:06
Location: NL

Re: BME 280 wrong temp value

#2 Post by Ath » 04 May 2022, 19:40

Often the sensor is mounted too close to an external heat source, that can be compensated by adjusting the 'Temperature offset' setting, in your case it should be -20.
Alternatively, if you need the original Humidity value (it may be correct, while the temperature is off), you can add this in the 'Formula' field of the 'Temperature' value: "%value%-2" (copy without the quotes).
/Ton (PayPal.me)

Trainer
Normal user
Posts: 23
Joined: 03 Apr 2020, 15:45

Re: BME 280 wrong temp value

#3 Post by Trainer » 04 May 2022, 19:53

the sensor is in the shade in its own 3d printed housing in which only the sensor is located.

TD-er
Core team member
Posts: 8643
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: BME 280 wrong temp value

#4 Post by TD-er » 04 May 2022, 22:01

When using the temperature offset in the BME280, the humidity is also compensated for this offset.
So no need to compensate the humidity as this is absolutely NOT a linear relation.

The typical 2 degree offset was also an issue on some (really old) builds of ESPEasy.
This may happen when the registers of the BME280 were not all read in 1 single I2C transmission.

What build of ESPEasy are you running?

Trainer
Normal user
Posts: 23
Joined: 03 Apr 2020, 15:45

Re: BME 280 wrong temp value

#5 Post by Trainer » 04 May 2022, 22:33

i ue the last fw "ESP_Easy_mega_20220427_normal_ESP8266_4M1M".

i set the offset for 2°C but now after the temp is falling it is again wrong :(

User avatar
Ath
Normal user
Posts: 3416
Joined: 10 Jun 2018, 12:06
Location: NL

Re: BME 280 wrong temp value

#6 Post by Ath » 04 May 2022, 22:40

And that housing has enough openings so the temperature can (quickly) adjust to the surrounding ambient temperature?
/Ton (PayPal.me)

TD-er
Core team member
Posts: 8643
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: BME 280 wrong temp value

#7 Post by TD-er » 04 May 2022, 22:54

Maybe also check the logs to see if you have read errors every now and then.

User avatar
ThomasB
Normal user
Posts: 1064
Joined: 17 Jun 2018, 20:41
Location: USA

Re: BME 280 wrong temp value

#8 Post by ThomasB » 05 May 2022, 01:42

the sensor is in the shade in its own 3d printed housing in which only the sensor is located.
I suggest posting a photo of your installed sensor. Photo should also show its placement from the ESP device.

- Thomas

TD-er
Core team member
Posts: 8643
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: BME 280 wrong temp value

#9 Post by TD-er » 05 May 2022, 09:30

And note the cable length!

Issues I've seen with the BME280:
- Reporting 2 degree too high (and thus humidity too low), on (really) old builds of ESPEasy
- Sensor heating itself, but that's less likely in a separate enclosure.
- Loose contacts or moisture shorting some pads => Check logs to see if there are faulty readings
- Too long I2C cabling, or missing pull-up resistors => lower I2C clock speed and check logs

Post Reply

Who is online

Users browsing this forum: Google [Bot] and 32 guests