BME280 humidity too high for 5 different parts - SparkFun Atmospheric Sensor Breakout (with Headers)

Sensors Environmental
1

For a laboratory setup, I am using BME280 - SparkFun Atmospheric Sensor Breakout (with Headers). I have ordered 5 items and none of them reads the humidity correctly (which is verified by measuring with independent two other sensors near the BME280). I use it in a temperature controlled room where the humidity should be 40% which is what the other sensors show. BME280s show at least 80% humidity and 3 of them even show always 100% (I think the reading is overflowing). I wonder if the soldering done in from the Sparkfun team had created an issue with the sensor?

Any help would be appreciated. thanks

2

Can you share a photo of the soldering/wiring?

Are they sharing the same bus, or are there any other items connected?

3

There’s no soldering that I did. I basically connected a single item using the I2c lines via simple jumper cables to an arduino. The temperature and the pressure works well. By different sensor I meant that I just disconnected one and tried the others so with the same configuration to see if maybe one sensor is good. However all had very high humidity readings yet not identical.

4

Datasheet has something about what you’re experiencing.

Reconditioning Procedure
After exposing the device to operating conditions, which exceed the limits specified in
section 1.2, e.g. after reflow, the humidity sensor may possess an additional offset. Therefore
the following reconditioning procedure is mandatory to restore the calibration state:

  1. Dry-Baking: 120 °C at <5% rH for 2 h
  2. Re-Hydration: 70 °C at 75% rH for 6 h
    or alternatively
  3. Dry-Baking: 120 °C at <5% rH for 2 h
  4. Re-Hydration: 25 °C at 75% rH for 24 h
    or alternatively after solder reflow only
  5. Do not perform Dry-Baking
  6. Ambient Re-Hydration: ~25 °C at >40% rH for >5d

Reflow happened when the board was assembled, give reconditioning a try and see if things improve.

5

Thanks for the instructions!!

Unfortunately I don’t have anything besides a regular oven which I can do the baking part but not the rehydration part. I would’ve expected sparkfun to do this already if the soldering is the cause.

Are there any tips on how you can do the rehydration part without a professional climate equipment?

6

Put the sensors in a sealed plastic container along with a clean, damp sponge for about a week.

7

I’ll try that thanks!

8

In my experience when these sensors ger really wet (like driving rain into my Stevenson screen) and the air droplets somehow get to the sensor, they start misbehaving and reading way too high.
They are cheap. If you can i suggest you switch to HDC3022 - it has an internal heating element helping the RH sensor cope with high humidity situations.
There is no extra wiring needed. This all is done via the SDA/SCL existing wires you use to read.
You just send 2 commands and the sensor either turns on or off its internal sensor heater.
If you measure only humidity, then using the heater is a good choice, but SDC3022 also measures temp, in which case I’d avoid using the heater and avoid artificially high temp readings - these cost less than $10. I did have to calibrate it (high RH readings are higher than in low RH readings when compared to a reference device). So, I had to build into my code to compensate for it in a gradual offset.

And since you are dealing with I2C, try to keep your cables under 2 feet if you can help it. Anything above 5 foot length will be prone to EM interference and could give spurious readings without a signal booster - troubleshooting at that point is hard, because you can’t even trust what your wire is passing through, let alone what the sensor is doing.
I learned this the hard way. Took me weeks to figure out my wires were a partial culprit.