diff --git a/TestBenchFramework/BenchControl/TestMethods/FlyingStartCollectionMethod/FlyingStartCollectionMethodSeq.cs b/TestBenchFramework/BenchControl/TestMethods/FlyingStartCollectionMethod/FlyingStartCollectionMethodSeq.cs
index 843622a78..358da05ee 100644
--- a/TestBenchFramework/BenchControl/TestMethods/FlyingStartCollectionMethod/FlyingStartCollectionMethodSeq.cs
+++ b/TestBenchFramework/BenchControl/TestMethods/FlyingStartCollectionMethod/FlyingStartCollectionMethodSeq.cs
@@ -456,6 +456,7 @@ namespace TBF.BenchControl.TestMethods.FlyingStartCollectionMethod
                         WaterMeters.iPerl.WaterMeter iPerl = (sensPath.RegisterReaders[i] as WaterMeters.iPerl.WaterMeter);
                         tstRslt.Meters[i].VolumeMeter = (float)(iPerl.VolumeLtrEnd - iPerl.VolumeLtrStart);
                         tstRslt.Meters[i].VolumeRef = tstRslt.VolumeCTV * (float)(iPerl.TimestampSecEnd - iPerl.TimestampSecStart) / tstRslt.Time;
+                        iPerl.VolumeLtrRef = (double)tstRslt.Meters[i].VolumeRef;
                     }
                     else
                     {
diff --git a/TestBenchFramework/BenchControl/TestMethods/iPerlCommunication/iPerlCommunicationForm.cs b/TestBenchFramework/BenchControl/TestMethods/iPerlCommunication/iPerlCommunicationForm.cs
index 11cb38962..02e823347 100644
--- a/TestBenchFramework/BenchControl/TestMethods/iPerlCommunication/iPerlCommunicationForm.cs
+++ b/TestBenchFramework/BenchControl/TestMethods/iPerlCommunication/iPerlCommunicationForm.cs
@@ -805,11 +805,9 @@ namespace TBF.BenchControl.TestMethods.iPerlCommunication
 
             CommErr error = CommErr.Write;
 
-			UInt16 factor = wm.CalibrationFactor;				/// Original calibration factor
-
             /// Write the calculated calibration factor
-            UInt16 newCalFactor = wm.CalculatedCalibrationFactor;
-            byte[] data = new byte[2] { (byte)(newCalFactor & 0x00FF), (byte)((newCalFactor >> 8) & 0x00FF) };
+            UInt16 newCalibFactor = wm.CalculateNewCalibFactor(wm.CalibrationFactor);
+            byte[] data = new byte[2] { (byte)(newCalibFactor & 0x00FF), (byte)((newCalibFactor >> 8) & 0x00FF) };
             for (int j = 0; j < MaxCommRetries; j++)
             {
                 if (0 == WriteRequestPort(boardNr, MessageID.Calibration, 2, 2, data, CommTimeout)) { error = CommErr.None; break; }
diff --git a/TestBenchFramework/BenchControl/WaterMeters/iPerl/WaterMeter.cs b/TestBenchFramework/BenchControl/WaterMeters/iPerl/WaterMeter.cs
index 31c26e1d2..d13e99afe 100644
--- a/TestBenchFramework/BenchControl/WaterMeters/iPerl/WaterMeter.cs
+++ b/TestBenchFramework/BenchControl/WaterMeters/iPerl/WaterMeter.cs
@@ -89,11 +89,23 @@ namespace TBF.BenchControl.WaterMeters.iPerl
 
         public ushort CalibrationFactor { get { return CalibrationStruct.Calibration; } }
 
-        public ushort CalculatedCalibrationFactor
+        public UInt16 CalculateNewCalibFactor(UInt16 originalCalibrationFactor)
         {
-            get
+            double volumeMeter = VolumeLtrEnd - VolumeLtrStart;
+            if (volumeMeter > 1E-2)
             {
-                return (UInt16)((double)CalibrationStruct.Calibration + 0.5);       /// TODO: real calculation
+                UInt16 newFactor = (UInt16)((double)originalCalibrationFactor * VolumeLtrRef / volumeMeter + 0.5);
+                log.InfoFormat("CalculateNewCalibFactor: orig={0} new={1} V_1={2} V_2={3} Vdiff={4} Vref={5}",
+                               originalCalibrationFactor, newFactor,
+                               VolumeLtrStart.ToString("F3"), VolumeLtrEnd.ToString("F3"), volumeMeter.ToString("F3"),
+                               VolumeLtrRef.ToString("F3"));
+                return newFactor;
+            }
+            else
+            {
+                log.ErrorFormat("CalculateNewCalibFactor: orig={0} new={0} (unchanged!) Vdiff={1}",
+                               originalCalibrationFactor, volumeMeter.ToString("F3"));
+                return originalCalibrationFactor;   /// Too small volume in the denominator -> no correction at all
             }
         }
 
@@ -108,10 +120,11 @@ namespace TBF.BenchControl.WaterMeters.iPerl
         private double volumeLtr;           /// 
         private double volumeLtr0;
 
-        public double VolumeLtrStart;
-        public double VolumeLtrEnd;
-        double volumeLtrEnd1;
-        double volumeLtrEnd2;
+        public double VolumeLtrStart;       /// Test start volume for metrology
+        public double VolumeLtrEnd;         /// Test end volume for metrology
+        public double VolumeLtrRef;         /// Reference volume or metrology
+        double volumeLtrEnd1;               /// auxiliary buffer1 to keep the end volume before test stops
+        double volumeLtrEnd2;               /// auxiliary buffer2 to keep the end volume before test stops
 
         ///
         /// Timestamp from the opto telegram