Custom input value

Hi, searched around without luck and need help with a thing.
I had build some easy voltage meter to monitor ups backups and other 12v things, just 2 resistors and a capacitor. The output value is around 1v and using the code below to upscale it to 12v.

    friendly_name: "Ups_Batteri"
    unit_of_measurement: 'volts'
    value_template: "{{ ((states('sensor.ups_router_voltage_2')|float -0.005 ) * 3.35 * 5)|round (1) }}"

The problem is the 12v value isnt linaer with the real 12v sourse, after some adjustment I got 14,2v instead of 13.9 and 11,8v instead of 12,0v. Is it possible to create a curve so the value in HA is same as the real value?

You can use the compensation integration to achieve such a result.

Thanks, just what I wanted. But cant get it to work, trying in template tester but it give me no value. “sensor.ups_router_voltage_2” is my input value.

    source: sensor.ups_router_voltage_2
    attribute: volume_level
    unit_of_measurement: dB
      - [0.2, -80.0]
      - [1.0, 0.0]

Does sensor.ups_router_voltage_2 really have an attribute called volume_level?
The sensor name kind of says it reads the voltage, not decibel unit_of_measurement: dB

No, it read voltage. But I thought the template dont care if it measure voltage or db, it just convert a value and show it with a unit.
Just copypaste from the example code and changed the input value with my to test if it works