DHT11-sensor needs offset

ESPHome
1

I have a DHT11-sensor in my garage. But I notice that it is roughly 2°C off.

Is there a way to offset, so the entity always is 2°C offset from its reading?

My Yaml for it is:

substitutions:
  name: esphome-web-0b9707
  friendly_name: ESPHome01

esphome:
  name: ${name}
  friendly_name: ${friendly_name}
  min_version: 2024.6.0
  name_add_mac_suffix: false
  project:
    name: esphome.web
    version: dev

esp8266:
  board: esp01_1m

# Enable logging
logger:

# Enable Home Assistant API
api:

# Allow Over-The-Air updates
ota:
- platform: esphome

# Allow provisioning Wi-Fi via serial
improv_serial:

wifi:
  # Set up a wifi access point
  ap: {}

# In combination with the `ap` this allows the user
# to provision wifi credentials to the device via WiFi AP.
captive_portal:

dashboard_import:
  package_import_url: github://esphome/example-configs/esphome-web/esp8266.yaml@main
  import_full_config: true

# To have a "next url" for improv serial
web_server:

# TEMPTEXT
sensor:
  - platform: dht
    pin: GPIO4
    temperature:
      name: Temperature
    humidity:
      name: Humidity
    model: dht11
    update_interval: 30s
2

Here my config

sensor:
#sensor: DHT22
  - platform: dht
    pin: GPIO22
    model: AM2302
    temperature:
      name: "Badezimmer Temperature"
      id: am2320_temp
      accuracy_decimals: 1
      filters:
        - round: 1 #  round to 1 decimal place mehr kann er nicht
        - offset: 0.37 # noch in Arbeit
    humidity:
      name: "Badezimmer Humidity"
      id: am2320_hym
      accuracy_decimals: 1
      filters:
        - round: 1 #  round to 1 decimal place mehr kann er nicht
        - offset: 0.00 # noch in Arbeit
    update_interval: 20s
1 Like
3 
sensor:
  - platform: dht
    pin: GPIO4
    temperature:
      name: Temperature
      filters:
        - offset: 2.0
....
1 Like
4

So easy then.
I missed the part with “filters”.
Just added the offset, and got error.

Will try and come back!

5

It worked as a sharm.
Thanks alot!

# TEMPTEXT
sensor:
  - platform: dht
    pin: GPIO4
    temperature:
      name: Temperature
      filters:
        - offset: -2.0
    humidity:
      name: Humidity
    model: dht11
    update_interval: 30s
6

I’ve experimented with these temperature sensors a lot; to then extent that I built a temperature controlled oven. The spec is +/- 2°C Yup, they can have an offset up to that amount. But also the measurement wil vary with the temperature. So its not just T=Tm + O! It’s T = S * Tm + O. S and O are specific to each device. Fortunately, S is usually pretty close to 1, but enought to be annoying.

These devices can be as much as 4°C off the actual temperature. Humidity also plays a small roll in the measurement. As I remember, they’re rated to be used from 0°C to 40°C. Mine, shielded from rain, only lasted a year in a garden environment. My experiments showed that the DHT12 was only slightly better than the DHT11.

-OSD

1 Like
7

The DHT style sensors were okay when all others were expensive and you didn’t really care that much about accuracy. Today, if you care at all about accuracy you should pick a better sensor.