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Noise sensor was permanently on 99dB and now is showing unrealistic values

Hello,
I would like to make get some background noise measurements so I plugged in again my SCK 2.1. After turning it on all the sensors seemed to work OK except for noise sensor that showed constant 99 dBA.
After plugging and un plugging around ( tests with and without battery plugged, charged battery vs uncharged ) the sensor started to show something different, around 70 dBA. But at some point climbed again to 99 dBA.
Then i’ve updated the FW to the current version on git, the SAM 0.9.6. There the behaviour is the same with the lectures falling abruplty several minutes after the SCK restart from 99dBA to around 70 dBA. Now the noise showed is steadily drecreasing ( in one hour it went from 74 dBA to 68 dBA ) but being at night and inside a house these measures are nonsense and not related with previous measured done on the exterior that show a maximum of 68 dBA at noon on the exterior, and a minimum of 53 dBA on the exterior.
You can see the screenshots with the strange behaviour.

Regards
I’ll will cite @oscgonfer as It seems an specialist on this subject.

Here there is the usual expected graph gathered by this same sensor on july:

Hi!

We found this issue could be related to water going inside the microphone. @oscgonfer and @victor are currently carrying out some research on the topic.

Don’t worry that we will find a good solution!

Thanks for the update.

In my concrete case I don’t recall having the sensor in a place where it could get direct liquid or vapour water exposure.

On the following attach one could see various days. It measures something but the values are far from previous lectures when it was working.![30|690x245(upload://zxigCjNc0aea4tifbr25OXp9AEl.png)

If the problem are water molecules trapped inside of the mems I could do the following tests if you provide enough information.
On my workplace we have vacuum ovens to heat up equipment and extract impurities from its surfaces ( by evaporation and suction ).
I could try to put the sensor board on that oven. In that case what temperature and pressure you’ll advise?

Regards

Hi @aquefotescriuretant,

Thanks for your support on this. We really appreciate your messages.

That possibility sounds amazing. From reading the datasheet of the ICS43432 (here), maximum ratings would be:

The rest of the sensors are more or less in the same range (except the light sensor), which goes only up to 100degC. In terms of pressure, we do not have much information, but what I would suggest is to go up to 100degC and maybe lower pressure until 30-40kPa or so (although it is difficult to know whether this will do anything or not).

PD: I believe you are in Cataluña?

Regards,

Óscar

Ok, nice to hear that.
Yes, from Catalonia.

When I do the test I’ll post it here.
Regards

1 Like

Check here:

We did a quick test reducing the pressure on the sensor board.
It was a short time under 3 millibars.
At the beginning it seemed to start at a lower readings on noise. After we situated the device on the outside with heavy rain ( not directly exposed to water ). It saturated again.

We’ll do more tests situating the device at less millibars during far longer time, at room temperature, in order to get evaporation of water due to the low pressure.