diff --git a/GUI_Elbow.py b/GUI_Elbow.py
index 7ecb25b0cd92127894f9b146765fc721ba0c6043..9eb15cad86659992c236bd38925d212b5e5f2ee4 100644
--- a/GUI_Elbow.py
+++ b/GUI_Elbow.py
@@ -623,10 +623,9 @@ class mainPanel(wx.Panel):
     def OnClicked_btn_uncertainty(self,e):
         # calculate the uncertainty for the flow meter
         if self.pathint.any():
-            self.fm_mean = np.zeros_like(self.pathint)
-            self.fm_std  = np.zeros_like(self.pathint)
-            
             if flow.case == "SingleElbow":
+                self.fm_mean = np.zeros((len(flow.Rk),len(flow.dist),len(flow.phi)))
+                self.fm_std  = np.zeros((len(flow.Rk),len(flow.dist),len(flow.phi)))
                 for i,rc in enumerate(flow.Rk):
                     for j,dist in enumerate(flow.dist):
                         for k,phi in enumerate(flow.phi[:,0]):
@@ -638,6 +637,8 @@ class mainPanel(wx.Panel):
                 self.regint_mean = interpol.RegularGridInterpolator((flow.Rk,flow.dist,flow.phi[:,0]),self.fm_mean,bounds_error = False,fill_value=None)
                 self.regint_std  = interpol.RegularGridInterpolator((flow.Rk,flow.dist,flow.phi[:,0]),self.fm_std,bounds_error = False,fill_value=None)
             else:
+                self.fm_mean = np.zeros((len(flow.Rk),len(flow.dl),len(flow.dist),len(flow.phi)))
+                self.fm_std  = np.zeros((len(flow.Rk),len(flow.dl),len(flow.dist),len(flow.phi)))
                 for i,rc in enumerate(flow.Rk):
                     for j,dl in enumerate(flow.dl):
                         for k,dist in enumerate(flow.dist):