Thingy52 Temperature resolution

[juu]

Hello,

I have used the Nordic Thingy application, I also used the Raspberry Pi Python interface and I observed the temperature measured.

The temperature is not stable and can go up to 1°C in 1 second then decrease. I don't understand where these measures are coming from.

The temperature and humidity sensor is the HTS221.

I have found here : https://learn.adafruit.com/adafruit-hts221-temperature-humidity-sensor

" The HTS221 can measure relative humidity from 0%-100% rH with a sensitivity of 0.004% and 3.5% accuracy. It can also measure temperature from -40 to 120 degrees C, with a resolution of 0.016°C with ±0.5 °C accuracy between 15 and +40 °C."

 

Best regards.

[haakonsh]

That's probably a rounding error. Are you parsing the temperature characteristic correctly? 

See the Environment service docs. 

Also, 

±0.5 °C accuracy

That's 1 degree celcius, exactly what you observe.  

[juu]

I am using the application from Nordic (Nordic Thingy), I guess they parsed correctly their own product.

haakonsh said:

±0.5 °C accuracy

Doesn't it mean that when I read 26°C, in reality it could be 25,5°C or 26,5°C ?

When I see a temperature going from 25°C to 26°C, for me it's more a resolution issue than an accuracy issue.

[haakonsh]

juu said:

Doesn't it mean that when I read 26°C, in reality it could be 25,5°C or 26,5°C ?

 Yes. 

juu said:

When I see a temperature going from 25°C to 26°C, for me it's more a resolution issue than an accuracy issue.

 Then it seems you're discarding the decimals. From the docs i linked to:

Temperature in Celsius

• int8_t - integer
• uint8_t - decimal

It might be that you're only using the integer byte

[juu]

From 25°C to 26°C was just an example, I do have the decimals.

In my screenshots in the first message you can see the temperature going from 26,8°C to 25,93°C in 1 second.

[haakonsh]

I'm sorry I can't see any such screenshot, do you mind sending the screenshot in a .zip folder? Devzone is a bit wonky sometimes...

[juu]

2843.Downloads.zip

[haakonsh]

That seems like a fairly normal temperature reading to me? 

How are you controlling for the environment? Do you use a temperature chamber?

[juu]

I am planning on using a temperature chamber to verify the accuracy of the measure.

on the image "Screenshot_2020-08-04-09-11-43-309_no.nordicsemi.android.nrfthingy"

The jump from 26,17°C to 26,80°C then 25,93°C in 2 seconds doesn't seem correct to me.

The temperature can't vary that fast.