salt_level_sensor.yaml

---
esphome:
  name: salt_level_sensor
  platform: ESP8266
  board: d1_mini

# WiFi connection, replace these with values for your WiFi.
wifi:
  ssid: !secret Wifi_SSID
  password: !secret Wifi_PWD

# Enable logging
logger:

# Enable Home Assistant API
api:

# Enable over-the-air updates.
ota:

# Enable Web server.
web_server:
  port: 80
# Sync time with Home Assistant.
time:
  - platform: homeassistant
    id: homeassistant_time

# Text sensors with general information.
text_sensor:
  # Expose ESPHome version as sensor.
  - platform: version
    name: salt_level_sensor ESPHome Version
  # Expose WiFi information as sensors.
  - platform: wifi_info
    ip_address:
      name: salt_level_sensor IP
    ssid:
      name: salt_level_sensor SSID
    bssid:
      name: salt_level_sensor BSSID

# Exposed switches.
# Switch to restart the salt_level_sensor.   
switch:
  - platform: restart
    name: "salt_level_sensor Restart"

sensor:
  # Uptime sensor.
  - platform: uptime
    name: salt_level_sensor Uptime

  # WiFi Signal sensor.
  - platform: wifi_signal
    name: salt_level_sensor WiFi Signal
    update_interval: 60s

  - platform: ultrasonic
    trigger_pin: D1
    echo_pin: D2
    name: "Saltlevel in percent"
    update_interval: 12h
    filters:
    # Calculates in %
    # Replace 0.42 by the height of your container. From the sensor to the bottom.
    # I used this website to know how I should multiply my values :https://www.skillsyouneed.com/num/percent-change.html 
    - lambda: return (0.42-x)*(100/0.42);
    unit_of_measurement: "%"
    
  - platform: ultrasonic
    trigger_pin: D1
    echo_pin: D2
    name: "Saltlevel in cm"
    update_interval: 12h
    filters:
    # Replace the 0.42 by the height of your container. From the sensor to the bottom.
    # I multiplied by 100 in order to get CM since the sensor works in meters
    - lambda: return (0.42-x)*100;
    unit_of_measurement: "cm"

Hi ... Just wondering if this code still works for you? I tried and can't seem to have 2 entities defined using "platform: ultrasonic".
What's really weird are the errors I get ... (pins 4 & 5)

I ended up having to do the following for the two sensors: In the case of my tank the sensor is located 83.5 cm from the bottom but I can only fill it to 72cm.

`sensor:
  - platform: ultrasonic
    trigger_pin: D1
    echo_pin: D2
    name: "Salt Level"
    update_interval: 60s
    filters:
    - lambda: return (0.835-x)*100;
    unit_of_measurement: "cm"
    id: salt_level
    
  - platform: template
    name: "Salt Level Percent"
    lambda: |-
      if (id(salt_level).state >= 0) {
        return (id(salt_level).state/72)*100;
      } else {
        return 0;
      }
    unit_of_measurement: "%"
    update_interval: 60s    `