Index: firmware/App/Controllers/LoadCell.c
===================================================================
diff -u -rbcb768dd6a13286e028533394916a9f69c9f254f -r819c167acffdca21fef98c4c6103ae09b5757c58
--- firmware/App/Controllers/LoadCell.c	(.../LoadCell.c)	(revision bcb768dd6a13286e028533394916a9f69c9f254f)
+++ firmware/App/Controllers/LoadCell.c	(.../LoadCell.c)	(revision 819c167acffdca21fef98c4c6103ae09b5757c58)
@@ -290,6 +290,26 @@
 
 /*********************************************************************//**
  * @brief
+ * The isLoadCellTared function returns load cell tare status
+ * for a given load cell ID.
+ * @details Inputs: none
+ * @details Outputs: load cell tare status
+ * @param loadCellID ID of load cell tare status
+ *************************************************************************/
+BOOL isLoadCellTared( LOAD_CELL_ID_T loadCellID )
+{
+    if ( fabs( loadcells[ loadCellID ].autoCalOffset ) < NEARLY_ZERO )
+    {
+        return false;
+    }
+    else
+    {
+        return true;
+    }
+}
+
+/*********************************************************************//**
+ * @brief
  * The tareLoadCell function sets the load cell auto calibration offset
  * for a given load cell ID.
  * @details Inputs: none
@@ -470,17 +490,25 @@
  *************************************************************************/
 static void monitorLoadCellsPrimaryBackupDriftOutOfRange( void )
 {
-    // TODO do we need this function at all?
-    F32 drift;
+    F32 drift = 0.0;
+    F32 loadCellADrift = 0.0;
+    F32 loadCellBDrift = 0.0;
+    BOOL isDriftOutOfRange = false;
 
-    F32 loadCellADrift = fabs( getLoadCellSmallFilteredWeight( LOAD_CELL_RESERVOIR_1_PRIMARY ) -
+    // Test is valid after load cells are tared
+    if ( isLoadCellTared( LOAD_CELL_RESERVOIR_1_PRIMARY ) && isLoadCellTared( LOAD_CELL_RESERVOIR_1_BACKUP ) )
+    {
+        loadCellADrift = fabs( getLoadCellSmallFilteredWeight( LOAD_CELL_RESERVOIR_1_PRIMARY ) -
                                getLoadCellSmallFilteredWeight( LOAD_CELL_RESERVOIR_1_BACKUP ) );
-
-    F32 loadCellBDrift = fabs( getLoadCellSmallFilteredWeight( LOAD_CELL_RESERVOIR_2_PRIMARY ) -
+    }
+    if ( isLoadCellTared( LOAD_CELL_RESERVOIR_2_PRIMARY ) && isLoadCellTared( LOAD_CELL_RESERVOIR_2_BACKUP ) )
+    {
+        loadCellBDrift = fabs( getLoadCellSmallFilteredWeight( LOAD_CELL_RESERVOIR_2_PRIMARY ) -
                                getLoadCellSmallFilteredWeight( LOAD_CELL_RESERVOIR_2_BACKUP ) );
+    }
 
-    BOOL isDriftOutOfRange = ( loadCellADrift > LOAD_CELL_PRIMARY_BACKUP_MAX_ALLOWED_DRIFT_GRAMS ) ||
-                             ( loadCellBDrift > LOAD_CELL_PRIMARY_BACKUP_MAX_ALLOWED_DRIFT_GRAMS );
+    isDriftOutOfRange = ( loadCellADrift > LOAD_CELL_PRIMARY_BACKUP_MAX_ALLOWED_DRIFT_GRAMS ) ||
+                        ( loadCellBDrift > LOAD_CELL_PRIMARY_BACKUP_MAX_ALLOWED_DRIFT_GRAMS );
 
     if ( TRUE == isDriftOutOfRange )
     {
@@ -492,9 +520,10 @@
         drift = ( loadCellADrift > loadCellBDrift ? loadCellADrift : loadCellBDrift );
     }
 
-    // TODO this alarm is disabled until a better drift algorithm is figured out. Drift check might be removed from the load cells
-    //checkPersistentAlarm( ALARM_ID_DG_LOAD_CELL_PRIMARY_BACKUP_DRIFT_OUT_OF_RANGE, isDriftOutOfRange, drift,
-     //                     LOAD_CELL_PRIMARY_BACKUP_MAX_ALLOWED_DRIFT_GRAMS );
+    // TODO Need data to set the proper drift range
+    // TODO Should this alarm be cleared when the condition goes away?
+    checkPersistentAlarm( ALARM_ID_DG_LOAD_CELL_PRIMARY_BACKUP_DRIFT_OUT_OF_RANGE, isDriftOutOfRange, drift,
+                          LOAD_CELL_PRIMARY_BACKUP_MAX_ALLOWED_DRIFT_GRAMS );
 }