Merge commit '12fce6c' into HEAD

# Conflicts:
#	index.js
#	src/configs/index.js
#	src/configs/machineGroupControl.json
#	src/helper/assetUtils.js
#	src/helper/childRegistrationUtils.js
#	src/helper/configUtils.js
#	src/helper/logger.js
#	src/helper/menuUtils.js
#	src/helper/menuUtils_DEPRECATED.js
#	src/helper/outputUtils.js
#	src/helper/validationUtils.js
#	src/measurements/Measurement.js
#	src/measurements/MeasurementContainer.js
#	src/measurements/examples.js
#	src/outliers/outlierDetection.js

src/measurements/MeasurementContainer.js

@@ -1,6 +1,7 @@
 const MeasurementBuilder = require('./MeasurementBuilder');
 const EventEmitter = require('events');
 const convertModule = require('../convert/index');
+const { POSITIONS } = require('../constants/positions');
 
 class MeasurementContainer {
   constructor(options = {},logger) {
@@ -478,7 +479,7 @@ class MeasurementContainer {
   getLaggedSample(lag = 1,requestedUnit = null ){
     const measurement = this.get();
     if (!measurement) return null;
-    
+
     let sample = measurement.getLaggedSample(lag);
     if (sample === null) return null;
 
@@ -554,7 +555,7 @@ class MeasurementContainer {
   }
 
   // Difference calculations between positions
-  difference({ from = "downstream", to = "upstream", unit: requestedUnit } = {}) {
+  difference({ from = POSITIONS.DOWNSTREAM, to = POSITIONS.UPSTREAM, unit: requestedUnit } = {}) {
     if (!this._currentType || !this._currentVariant) {
       if (this.logger) {
         this.logger.warn('difference() ignored: type and variant must be specified');
@@ -682,6 +683,8 @@ class MeasurementContainer {
     this._currentType = null;
     this._currentVariant = null;
     this._currentPosition = null;
+    this._currentDistance = null;
+    this._unit = null;
   }
 
   // Helper method for value conversion
@@ -739,11 +742,11 @@ class MeasurementContainer {
 
   _convertPositionStr2Num(positionString) {
     switch(positionString) {
-      case "atEquipment":
+      case POSITIONS.AT_EQUIPMENT:
         return 0;
-      case "upstream":
+      case POSITIONS.UPSTREAM:
         return Number.POSITIVE_INFINITY;
-      case "downstream":
+      case POSITIONS.DOWNSTREAM:
         return Number.NEGATIVE_INFINITY;
       
       default:
@@ -756,13 +759,13 @@ class MeasurementContainer {
 
   _convertPositionNum2Str(positionValue) {
     if (positionValue === 0) {
-      return "atEquipment";
+      return POSITIONS.AT_EQUIPMENT;
     }
     if (positionValue < 0) {
-      return "upstream";
+      return POSITIONS.UPSTREAM;
     }
     if (positionValue > 0) {
-      return "downstream";
+      return POSITIONS.DOWNSTREAM;
     }
     if (this.logger) {
       this.logger.warn(`Invalid position provided: ${positionValue}`);