Hello all, I’m trying to understand the readings I’m getting from an ESP-01s & dallas temp sensor.
I’m using a waterproof sensor to measure the temps in a freezer but some reason I’m getting shark fin readings I can’t explain as seen below.
once the sensor is reading the right temps (-17C) it slowly ‘warms’ up and then going back to the correct reading. the cycle is pretty stable as it takes 18 mins to reach -17 and then 34 mins to go up to -10 and then the cycle repeats. I removed the sensor from the freezer and ambient temperature seem to work well. restarting doesn’t change anything
Power supply is from a stabilised source , the range of the Dallas sensor goes from -50 to +125 C so I’m not hitting physical limits here.
I used to measure my freezer. The curve looked like that. But not as dramatic that. Going from -17 -> -10 in just 18 min, My did only varied a few degrees. Every time the compressor started it went down and then it slowly went up.
Have you tried to pack some put the sensor under som frozen stuff from the freezer and see if that changes the curve. If it still going in the same pattern the sensor seems off. If the temperature curve become stable.
Maybe your freezer is behaving odd or you are measuring on a bad spot. Then you probably need to check it against another thermometer.
Mine is the same shark fin profile. I have one DS18B20 inside the freezer and one SI7021 temp/hum outside, to measure the room temperature in the garage.
You can see from the screenshot that the temp goes down to about -20 in about 50 minutes, then slowly up to about -4 in about 3,5 hours.
Did moving the sensor solve your problems? Mine is at the top, right next to the door.
The thing I don’t quite understand is that you can see the SI7021 fluctuate at the same time as the DS18B20
I didn’t move the sensor, my goal was to detect an open door, the shark fin profile is as designed , the freezer averages out on the set temperature.
My sensor is next to the door opening at the top. When the door is open too long, temp rises to above 0 very quickly which triggers the alarm.
Happy with this solution and it serves the need.
as for the hum sensor, assuming temperature also affects humidity so you’d expect see a similar graph.
I installed a second DS18B20 sensor in the middle of the freezer, and the temperature still fluctuates, but now the temperature is always below 16,5 degrees celcius. (- 16,5 to - 24) So everything good.
The temperature close to the door just has that big fluctuations (-3,5 to -22)