to_ntc_resistance

Convert your sensor values available as temperature into corresponding resistance values using an NTC characteristic curve.

Configuration variables:

• calibration (Required): calibration data.

A resistance/temperature characteristic curve is required to use this filter. This can be taken from a corresponding diagram in a data sheet. If you do not have access to the data sheet or want to calculate these values yourself, you must first measure three resistance values at different temperatures. Heat or cool the NTC to three different temperatures (preferably widely separated temperatures) and note the resistance values at these temperatures. Then enter these values in the calibration parameter:

- platform: template
  id: to_ntc_resistance_sensor1
  unit_of_measurement: "Ohm"
  lambda: |-
    return id(some_sensor).state;
  update_interval: 1s
  filters:
    - to_ntc_resistance:
        calibration:
          - 10.0kOhm -> 25°C
          - 27.219kOhm -> 0°C
          - 14.674kOhm -> 15°C

The filter determines coefficients for the Steinhart-Hart_ equation from the specified pairs of values which can also be specified directly as an alternative.

Steinhart-Hart

- platform: template
  id: to_ntc_resistance_sensor2
  unit_of_measurement: "Ohm"
  lambda: |-
    return id(some_sensor).state;
  update_interval: 1s
  filters:
    - to_ntc_resistance:
        calibration:
          a: 1.439114856904070E-03
          b: 2.693066430764570E-04
          c: 1.653440958554570E-07

To send the resistance value generated by this sensor to an output component, e.g. a digital potentiometer or a DAC, the sensor automation on_value can be used. This makes it possible, for example, to replace a physical NTC and thus make it smart.

An output component can accept values in the range of 0..1 (see output.set_level Action), so that scaling with the actual resistance value of the simulated NTC is required.

on_value:
  then:
    - output.set_level:
        id: output_id
        level: !lambda return x / 100000.0;