Issue #24: Implement new handling for Unstable flag.

* Unstable flag will now be set, whenever the output of the moving average filter
  differs more than 10 Ohms from the measured prefilterd input.

stm-firmware/include/reflow-controller/adc-meas.h

@@ -44,6 +44,11 @@
   */
 #define ADC_PT1000_FILTER_WEIGHT_FAST 0.05
 
+/**
+ * @brief Difference in Ohm between filter input and output that determines if the filter is stable or unstable.
+ */
+#define ADC_PT1000_FILTER_UNSTABLE_DIFF 10
+
 /**
  * @brief ADC channel number of PT1000 sensor input
  */
@@ -64,12 +69,6 @@
  */
 #define ADC_PT1000_PIN 2U
 
-/**
- * @brief The cycle count the moving average filter is labeled 'instable' after startup of the measurement or changing
- * the alpha value @ref ADC_PT1000_FILTER_WEIGHT
- */
-#define ADC_FILTER_STARTUP_CYCLES 800U
-
 /**
  * @brief The delay value programmed into the sample timer
  */