HTU21D returns humidity above 100%

LuckyTriple7 commented 3 years ago

Operating environment/Installation (Hass.io/Docker/pip/etc.):

HASSOS, HASS 2021.06.02

ESP8266 NodeMCU v3

ESPHome version: V1.18

Affected component: HTU21D Temperature+Humidity Sensor

Description of problem:

HTU21D reports Humidity above 100%. These are unrealistic values. Maximum humidity is 100%

Problem-relevant YAML-configuration entries:

sensor:

platform: htu21d temperature: icon: mdi:thermometer name: Temperatur ${devicename_short} id: temp humidity: icon: mdi:water-percent name: Luftfeuchtigkeit ${devicename_short} id: humi update_interval: 60s


**Logs (if applicable):**
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[08:18:28][D][htu21d:052]: Got Temperature=17.1°C Humidity=101.7%



**Additional information and things you've tried:**

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Fusseldieb commented 3 years ago

From https://forums.adafruit.com/viewtopic.php?f=22&t=108435:

The higher-than-100% output you're seeing is a side effect of the humidity sensor absorbing too much water during the fog.

The sensor assumes that its sense cap will produce a specific reading at a specific temperature and humidty level.. usually 70% humidity at 25C. A sense cap that's been exposed to too much water will produce a higher reading than expected at the reference temperature and humidity levels. Exposing the sense cap to long periods of 100% humidity (like fog) will pick up that kind of offset.

You have two options:

1) You can declare the sensor dead and get a new one.

2) You can try to recondition the sensor by putting it in a 120C oven for about an hour to evaporate all the water stored in the sense cap, then let the sensor sit in a container at 70% humidity and 25C temperature for 24 hours.

This isn't an issue related to ESPHome.

LuckyTriple7 commented 3 years ago

Thank you for the information. the sensor is in a greenhouse. The values above 100% occur at night. When the windows are opened in the morning, the values are correct again. I have created a filter which filters out the values above 100%.

I hope the code is correct

      filters:
        - lambda: |-
            float MIN_VALUE = 1;
            float MAX_VALUE = 100.0;
            if (MIN_VALUE <= x && x <= MAX_VALUE) return x;

Fusseldieb commented 3 years ago

Nice to know!

It will certainly help others.

If you want, you can close this issue :)

esphome / issues

HTU21D returns humidity above 100% #2095