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A very simple method (no floating point, no algebraic formulas) for linear conversion of sensor output data to human-understandable units.

Two points are given: Sensor output 400 and 1200 correspond to 10 and 36.3 degrees Celsius respectively.
To get rid of floating point, we calculate Celsius in tenths of degrees:

  Sensor  Celsius
   400     100
  1200     363
  (800)   (263)  (Distance)

Let's take:

  SensorZ     = the given sensor value closest to zero (400)
  CelsiusZ    = the corresponding Celsius value (100)
  SensorDist  = distance between the two sensor values (800)
  CelsiusDist = distance between the two Celsius values (263)

Then the conversion looks like this:

  : >CELSIUS    ( sensor -- celsius )
    SensorZ -   CelsiusDist SensorDist */   CelsiusZ + ;

The working forth definition is:

  : >CELSIUS ( sensor -- celsius ) 400 - 263 800 */ 100 + ;

NEGATE must be inserted after */ when increasing sensor values correspond to decreasing Celsius values.

  Sensor  Celsius
   400     363
  1200     100
  (800)   (263)  (Distance)

The forth definition:

  : >CELSIUS ( sensor -- celsius ) 400 - 263 800 */ NEGATE 363 + ;

( an,jan2025)