Temperature is never below -1.8 C

[ilkkao]

dmesg output: [ 2.225797] usb 1-1.5: Product: TEMPer2_M12_V1.3

Command I use:

$ raspberrypi  ~/g/temper-python> temper-poll -s 1                                                                                                                                                    
Found 1 devices
Device #0: -1.8°C 28.7°F

Result in Finland currently:

During the daytime, temperature is correctly reported. But at night when it gets freezing, values never go below -1.8C. In reality, it gets colder than that.

My temper device should work up to -40C. Could it be that something changes at -1.8C regarding how the value is read? I'm also wondering if my device is faulty but that doesn't feel likely as day temperatures are very accurate.

[ilkkao]

I added print to see the raw response byte array from the sensor:

 raspberrypi  ~/g/temper-python> /home/pi/.local/bin/temper-poll -s 1                                                                                                                               master!
Found 1 devices
{'temp_data': array('B', [128, 4, 5, 128, 254, 48, 191, 107]), 'humidity_data': None}
Device #0: -1.8°C 28.7°F
[wait couple minutes]
 raspberrypi  ~/g/temper-python> /home/pi/.local/bin/temper-poll -s 1                                                                                                                               Found 1 devices
{'temp_data': array('B', [128, 4, 5, 144, 254, 48, 191, 107]), 'humidity_data': None}
Device #0: -1.8°C 28.7°F

Are there any kind of manufacturer specs available?

[ilkkao]

Second sensor value seems to simply be an be 16-bit big endian integer from offset 4. Seems that my problem is that it never goes below [254 48]. So maybe a HW problem after all. I'd be interested to hear if somebody else has seen this.

[kl1lercher]

Same here for me, Temperature is never below -1.6°C. As i have two sensors i've changed positions (inside/outside a vice versa) but still temperature is never below -1.6°C. I am still checking data output to try to find out if it's a hardware problem (TEMPerV1.4)

[ilkkao]

My sensor started to work again when temperature went below ~ -4C (can't remember the exact value, the sensor is offline now).

Not sure at all what the problem is at this point.

[ilkkao]

Winter came so I was able to debug this bit further. My sensor returns -1.8C when the temperature is between 0..-1.8C. It works just fine when the temperature is outside of this range, i.e >0 or <1.8.

A strange HW flaw is my guess. Feel free to close this issue.

[Starfight]

Not exactly the same but for my temper temperature is never below 19.5°C. Work well above this value.