Thermocouple type K conversion

Cargo.toml

@@ -41,7 +41,7 @@ version = "0.3.*"
 version = "0.4.*"
 # Serialization
 [workspace.dependencies.parity-scale-codec]
-version = "3.5.*"
+version = "3.6.*"
 default-features = false
 # Embedded-HAL
 [workspace.dependencies.embedded-hal]
@@ -132,6 +132,7 @@ thermocouple_k = []
 [dependencies]
 uom = { workspace = true }
 parity-scale-codec = { workspace = true }
+libm = { workspace = true }
 
 #---------------------------------------------------------------------------------------------------------------------
 #----- Profiles ------------------------

src/transducer/conversion/thermocouples/type_k.rs

@@ -1,4 +1,5 @@
 use crate::transducer::InvalidValue;
+use libm::powf;
 use uom::si::electric_potential::{millivolt, volt};
 use uom::si::f32;
 use uom::si::thermodynamic_temperature::degree_celsius;
@@ -26,8 +27,7 @@ pub fn convert(
         let mv_pow7 = mv_pow6 * mv;
         let mv_pow8 = mv_pow7 * mv;
 
-        let celsius = 1.0
+        let celsius = 2.5173462E+1 * mv
-            + 2.5173462E+1 * mv
             + -1.1662878 * mv_pow2
             + -1.0833638 * mv_pow3
             + -8.9773540E-1 * mv_pow4
@@ -42,8 +42,7 @@ pub fn convert(
         let mv_pow8 = mv_pow7 * mv;
         let mv_pow9 = mv_pow8 * mv;
 
-        let celsius = 1.0
+        let celsius = 2.508355E+1 * mv
-            + 2.508355E+1 * mv
             + 7.860106E-2 * mv_pow2
             + -2.503131E-1 * mv_pow3
             + 8.315270E-2 * mv_pow4
@@ -72,21 +71,47 @@ pub fn convert(
 pub fn r_junction_offset_poly(
     temperature: f32::ThermodynamicTemperature,
 ) -> Result<f32::ElectricPotential, InvalidValue> {
-    const T0: f32 = 2.5000000E+01;
-    const V0: f32 = 1.0003453E+00;
-    const P1: f32 = 4.0514854E-02;
-    const P2: f32 = -3.8789638E-05;
-    const P3: f32 = -2.8608478E-06;
-    const P4: f32 = -9.5367041E-10;
-    const Q1: f32 = -1.3948675E-03;
-    const Q2: f32 = -6.7976627E-05;
-
     let celsius = temperature.get::<degree_celsius>();
-    if celsius >= -20.0 && celsius <= 70.0 {
+    let cel_pow2 = celsius * celsius;
-        let offset_tcj = celsius - T0;
+    let cel_pow3 = cel_pow2 * celsius;
-        let numerator = offset_tcj + (P1 + offset_tcj * (P2 + offset_tcj * (P3 + P4 * offset_tcj)));
+    let cel_pow4 = cel_pow3 * celsius;
-        let denominator = 1.0 + offset_tcj * (Q1 + Q2 * offset_tcj);
+    let cel_pow5 = cel_pow4 * celsius;
-        let mv = V0 + numerator / denominator;
+    let cel_pow6 = cel_pow5 * celsius;
+    let cel_pow7 = cel_pow6 * celsius;
+    let cel_pow8 = cel_pow7 * celsius;
+    let cel_pow9 = cel_pow8 * celsius;
+
+    if celsius >= -270.0 && celsius < 0.0 {
+        let cel_pow10 = cel_pow9 * celsius;
+
+        let mv = 0.394501280250E-01 * celsius
+            + 0.236223735980E-04 * cel_pow2
+            + -0.328589067840E-06 * cel_pow3
+            + -0.499048287770E-08 * cel_pow4
+            + -0.675090591730E-10 * cel_pow5
+            + -0.574103274280E-12 * cel_pow6
+            + -0.310888728940E-14 * cel_pow7
+            + -0.104516093650E-16 * cel_pow8
+            + -0.198892668780E-19 * cel_pow9
+            + -0.163226974860E-22 * cel_pow10;
+
+        Ok(f32::ElectricPotential::new::<millivolt>(mv))
+    } else if celsius >= 0.0 && celsius <= 1372.0 {
+        let base = celsius - 0.126968600000E+03;
+        let exp = -0.118343200000E-03 * (base * base);
+        let addition = powf(0.1185976, exp);
+
+        let mv = -0.176004136860E-01
+            + 0.389212049750E-01 * celsius
+            + 0.185587700320E-04 * cel_pow2
+            + -0.994575928740E-07 * cel_pow3
+            + 0.318409457190E-09 * cel_pow4
+            + -0.560728448890E-12 * cel_pow5
+            + 0.560750590590E-15 * cel_pow6
+            + -0.320207200030E-18 * cel_pow7
+            + 0.971511471520E-22 * cel_pow8
+            + -0.121047212750E-25 * cel_pow9
+            + addition;
 
         Ok(f32::ElectricPotential::new::<millivolt>(mv))
     } else {
@@ -94,11 +119,12 @@ pub fn r_junction_offset_poly(
     }
 }
 
+#[inline]
 pub fn r_junction_offset_lin(
     temperature: f32::ThermodynamicTemperature,
 ) -> Result<f32::ElectricPotential, InvalidValue> {
     let celsius = temperature.get::<degree_celsius>();
-    if celsius >= -2.0 && celsius <= 1000.0 {
+    if celsius >= -2.0 && celsius <= 800.0 {
         let mv = 0.041 * celsius;
         Ok(f32::ElectricPotential::new::<millivolt>(mv))
     } else {