From 5386d2a2bfcb79da7f52add0a1560fa71f8228c9 Mon Sep 17 00:00:00 2001
From: Zachary Sunforge <zachary.sunforge@bfpower.io>
Date: Thu, 6 Jul 2023 22:40:54 -0700
Subject: [PATCH] Thermocouple type K conversion

---
 Cargo.toml                                    |  3 +
 src/transducer/conversion/mod.rs              |  4 ++
 .../conversion/thermocouples/mod.rs           |  2 +
 .../conversion/thermocouples/type_k.rs        | 66 +++++++++++++++++++
 4 files changed, 75 insertions(+)
 create mode 100644 src/transducer/conversion/thermocouples/mod.rs
 create mode 100644 src/transducer/conversion/thermocouples/type_k.rs

diff --git a/Cargo.toml b/Cargo.toml
index 513db1c..fd9fb6f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -126,6 +126,9 @@ repository.workspace = true
 readme.workspace = true
 license.workspace = true
 
+[features]
+thermocouple_k = []
+
 [dependencies]
 uom = { workspace = true }
 parity-scale-codec = { workspace = true }
diff --git a/src/transducer/conversion/mod.rs b/src/transducer/conversion/mod.rs
index e69de29..fe6f177 100644
--- a/src/transducer/conversion/mod.rs
+++ b/src/transducer/conversion/mod.rs
@@ -0,0 +1,4 @@
+mod thermocouples;
+
+#[cfg(feature = "thermocouple_k")]
+pub use thermocouples::type_k as thermocouple_k;
\ No newline at end of file
diff --git a/src/transducer/conversion/thermocouples/mod.rs b/src/transducer/conversion/thermocouples/mod.rs
new file mode 100644
index 0000000..9ce86f4
--- /dev/null
+++ b/src/transducer/conversion/thermocouples/mod.rs
@@ -0,0 +1,2 @@
+#[cfg(feature = "thermocouple_k")]
+pub mod type_k;
\ No newline at end of file
diff --git a/src/transducer/conversion/thermocouples/type_k.rs b/src/transducer/conversion/thermocouples/type_k.rs
new file mode 100644
index 0000000..e59b39e
--- /dev/null
+++ b/src/transducer/conversion/thermocouples/type_k.rs
@@ -0,0 +1,66 @@
+use crate::transducer::InvalidValue;
+use uom::si::electric_potential::millivolt;
+use uom::si::f32;
+use uom::si::thermodynamic_temperature::degree_celsius;
+
+/// Convert from a voltage produced by a type k thermocouple to a temperature.
+///
+/// This function uses the [NIST type K thermocouple linearisation polynomial](https://srdata.nist.gov/its90/type_k/kcoefficients_inverse.html).
+pub fn convert(
+    voltage: f32::ElectricPotential,
+    cold_junction: f32::ThermodynamicTemperature,
+) -> Result<f32::ThermodynamicTemperature, InvalidValue> {
+    //TODO: Add cold junction correction
+    let mv = voltage.get::<millivolt>();
+    let mv_pow2 = mv * mv;
+    let mv_pow3 = mv_pow2 * mv;
+    let mv_pow4 = mv_pow3 * mv;
+    let mv_pow5 = mv_pow4 * mv;
+    let mv_pow6 = mv_pow5 * mv;
+
+    if mv >= -5.891 && mv <= 0.0 {
+        let mv_pow7 = mv_pow6 * mv;
+        let mv_pow8 = mv_pow7 * mv;
+
+        let celsius = 1.0
+            + 2.5173462e1 * mv
+            + -1.1662878 * mv_pow2
+            + -1.0833638 * mv_pow3
+            + -8.9773540e-1 * mv_pow4
+            + -3.7342377e-1 * mv_pow5
+            + -8.6632643e-2 * mv_pow6
+            + -1.0450598e-2 * mv_pow7
+            + -5.1920577e-4 * mv_pow8;
+
+        Ok(f32::ThermodynamicTemperature::new::<degree_celsius>(celsius))
+    } else if mv > 0.0 && mv < 20.644 {
+        let mv_pow7 = mv_pow6 * mv;
+        let mv_pow8 = mv_pow7 * mv;
+        let mv_pow9 = mv_pow8 * mv;
+
+        let celsius = 1.0
+            + 2.508355e1 * mv
+            + 7.860106e-2 * mv_pow2
+            + -2.503131e-1 * mv_pow3
+            + 8.315270e-2 * mv_pow4
+            + -1.228034e-2 * mv_pow5
+            + 9.804036e-4 * mv_pow6
+            + -4.413030e-5 * mv_pow7
+            + 1.057734e-6 * mv_pow8
+            + -1.052755e-8 * mv_pow9;
+
+        Ok(f32::ThermodynamicTemperature::new::<degree_celsius>(celsius))
+    } else if mv >= 20.644 && mv <= 54.886 {
+        let celsius = 1.318058e2
+            + 4.830222e1 * mv
+            + -1.646031 * mv_pow2
+            + 5.464731e-2 * mv_pow3
+            + -9.650715e-4 * mv_pow4
+            + 8.802193e-6 * mv_pow5
+            + -3.110810e-8 * mv_pow6;
+
+        Ok(f32::ThermodynamicTemperature::new::<degree_celsius>(celsius))
+    } else {
+        Err(InvalidValue)
+    }
+}