feat(thermocycler-gen2): ignore thermistor uniformity checks below 7.…

…5 degrees (#428) * Add some leniency to uniformity checks below 7.5 degrees C
Opentrons · Nov 17, 2022 · 043804b · 043804b
1 parent 5f63649
commit 043804b
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Showing 3 changed files with 31 additions and 1 deletion.
diff --git a/stm32-modules/include/thermocycler-gen2/thermocycler-gen2/plate_control.hpp b/stm32-modules/include/thermocycler-gen2/thermocycler-gen2/plate_control.hpp
@@ -100,6 +100,13 @@ class PlateControl {
     static constexpr double TARGET_ADJUST_FOR_COLD_TARGET = -5.0F;
     /** Extra factor to multiply the proportioal band by */
     static constexpr double PROPORTIONAL_BAND_EXTRA_FACTOR = 2.0F;
+    /**
+     * When performing the thermistor drift check, this is the max point
+     * below which errors are ignored. This is added to prevent unnecesary
+     * error messages during long periods below 8º where temperature may
+     * drift more than our normal spec BUT will not affect the samples.
+     */
+    static constexpr double DRIFT_CHECK_IGNORE_MAX_TEMP = 7.5;
 
     PlateControl() = delete;
     /**

diff --git a/stm32-modules/thermocycler-gen2/src/plate_control.cpp b/stm32-modules/thermocycler-gen2/src/plate_control.cpp
@@ -304,7 +304,8 @@ auto PlateControl::reset_control(thermal_general::HeatsinkFan &fan) -> void {
         min = std::min(temperature, min);
         max = std::max(temperature, max);
     }
-    return std::abs(max - min) <= THERMISTOR_DRIFT_MAX_C;
+    return (std::abs(max - min) <= THERMISTOR_DRIFT_MAX_C) ||
+           (max <= DRIFT_CHECK_IGNORE_MAX_TEMP);
 }
 
 [[nodiscard]] auto PlateControl::get_peltier_temps() const

diff --git a/stm32-modules/thermocycler-gen2/tests/test_plate_control.cpp b/stm32-modules/thermocycler-gen2/tests/test_plate_control.cpp
@@ -201,6 +201,28 @@ TEST_CASE("PlateControl drift error check") {
                 THEN("the result is false") { REQUIRE(result == false); }
             }
         }
+        GIVEN("uniform cold temperature across thermistors") {
+            constexpr double target = 4;
+            set_temp(thermistors, target);
+            WHEN("checking for thermistor drift") {
+                auto result = plateControl.thermistor_drift_check();
+                THEN("the result is true") { REQUIRE(result == true); }
+            }
+            AND_GIVEN("thermistors out of spec BUT under 7.5") {
+                thermistors.at(THERM_BACK_LEFT).temp_c = 0.5;
+                thermistors.at(THERM_BACK_RIGHT).temp_c = 7;
+                THEN("thermistor drift error does not occur") {
+                    REQUIRE(plateControl.thermistor_drift_check());
+                }
+            }
+            AND_GIVEN("thermistors out of spec and a resistor exceeds 7.5") {
+                thermistors.at(THERM_BACK_LEFT).temp_c = 0.5;
+                thermistors.at(THERM_BACK_RIGHT).temp_c = 8;
+                THEN("thermistor drift error occurs") {
+                    REQUIRE(!plateControl.thermistor_drift_check());
+                }
+            }
+        }
     }
 }