diff --git a/TBF/BenchControl/TestMethods/iPerlCommunication/iPerlHead/FlowDirectionDetection.cs b/TBF/BenchControl/TestMethods/iPerlCommunication/iPerlHead/FlowDirectionDetection.cs
index 4cf86494a..9b6d3c9a6 100644
--- a/TBF/BenchControl/TestMethods/iPerlCommunication/iPerlHead/FlowDirectionDetection.cs
+++ b/TBF/BenchControl/TestMethods/iPerlCommunication/iPerlHead/FlowDirectionDetection.cs
@@ -8,14 +8,16 @@ namespace TBF.BenchControl.TestMethods.iPerlCommunication.iPerlHead
 {
     public class FlowDirectionDetection
     {
-        readonly int fifoSize;
+        const int FIFO_SIZE = 64;               /// 8 sec. @ 8Hz
+        const double MAX_OPTO_DROPOUT = 4.5;    /// sec.
         
-        Int64[] volumeRawFifo;          /// Volume FIFO buffer
-        Int64[] timestampFifo;          /// Timestamp FIFO buffer
 
-        int fifoCount;                  /// Number of valid FIFO items
-        int fifoIx;                     /// Index of the next FIFO item
-        DateTime lastFifoWriteTime;     /// Time of the last write to FIFO
+        Int64[] volumeRawFifo;                  /// Volume FIFO buffer
+        Int64[] timestampFifo;                  /// Timestamp FIFO buffer
+
+        int fifoCount;                          /// Number of valid FIFO items
+        int fifoIx;                             /// Index of the next FIFO item
+        DateTime lastFifoWriteTime;             /// Time of the last write to FIFO
 
         ///
         /// Sums for linear regression calculation
@@ -26,11 +28,10 @@ namespace TBF.BenchControl.TestMethods.iPerlCommunication.iPerlHead
         decimal sumY;
         decimal N;
 
-        public FlowDirectionDetection(int fifoSize)
+        public FlowDirectionDetection()
         {
-            this.fifoSize = fifoSize;
-            volumeRawFifo = new Int64[fifoSize];
-            timestampFifo = new Int64[fifoSize];
+            volumeRawFifo = new Int64[FIFO_SIZE];
+            timestampFifo = new Int64[FIFO_SIZE];
             ClearFifo();
         }
 
@@ -62,7 +63,7 @@ namespace TBF.BenchControl.TestMethods.iPerlCommunication.iPerlHead
             ///
             /// Update sums for linear regression calculation
             ///
-            if (fifoCount == fifoSize)
+            if (fifoCount == FIFO_SIZE)
             {
                 /// Buffer is already full, the oldest item will be re-written
                 sumXX -= timestampFifo[fifoIx] * timestampFifo[fifoIx];
@@ -82,8 +83,8 @@ namespace TBF.BenchControl.TestMethods.iPerlCommunication.iPerlHead
             ///
             volumeRawFifo[fifoIx] = volumeRaw;
             timestampFifo[fifoIx] = timestamp;
-            fifoIx = (fifoIx + 1) % fifoSize;
-            fifoCount = Math.Min(fifoCount + 1, fifoSize);
+            fifoIx = (fifoIx + 1) % FIFO_SIZE;
+            fifoCount = Math.Min(fifoCount + 1, FIFO_SIZE);
             lastFifoWriteTime = DateTime.Now;
         }
 
@@ -94,7 +95,7 @@ namespace TBF.BenchControl.TestMethods.iPerlCommunication.iPerlHead
         /// <returns>true when data valid</returns>
         public bool AreFifoDataValid()
         {
-            return (DateTime.Now.Subtract(lastFifoWriteTime).TotalSeconds <= 2.5) && (fifoCount == fifoSize);
+            return (DateTime.Now.Subtract(lastFifoWriteTime).TotalSeconds <= MAX_OPTO_DROPOUT) && (fifoCount == FIFO_SIZE);
         }
 
 
diff --git a/TBF/BenchControl/TestMethods/iPerlCommunication/iPerlHead/IperlHead.cs b/TBF/BenchControl/TestMethods/iPerlCommunication/iPerlHead/IperlHead.cs
index 4f19171a4..09ac02022 100644
--- a/TBF/BenchControl/TestMethods/iPerlCommunication/iPerlHead/IperlHead.cs
+++ b/TBF/BenchControl/TestMethods/iPerlCommunication/iPerlHead/IperlHead.cs
@@ -24,8 +24,6 @@ namespace TBF.BenchControl.TestMethods.iPerlCommunication.iPerlHead
 		private static readonly ILog log = LogManager.GetLogger(typeof(IperlHead));
         public override string ToString() { return string.Format("iPerl({0})", Cfg.ToString(1)); }
 
-        const int FifoSize = 32;        /// 4s @ 8Hz
-
 		readonly IperlHeadCfg iperlHeadCfg;
 
         public int RfidComPortNr { get { return iperlHeadCfg.RfidComPortNr; } }
@@ -354,7 +352,6 @@ namespace TBF.BenchControl.TestMethods.iPerlCommunication.iPerlHead
 		///
         /// Timestamp from the opto telegram
         ///
-        bool lastTimestampValid;
         private Int64 lastTimestamp;
         private double timestampSec;
         private double timestampSec0;
@@ -393,7 +390,7 @@ namespace TBF.BenchControl.TestMethods.iPerlCommunication.iPerlHead
 		public IperlHead(Generic.IComponentCfg cfg)
 			: base(cfg)
         {
-            flowDirectionDetection = new FlowDirectionDetection(FifoSize);
+            flowDirectionDetection = new FlowDirectionDetection();
 
             ClearData();
 
diff --git a/TBF/Properties/AssemblyInfo.cs b/TBF/Properties/AssemblyInfo.cs
index 32ac37b22..198552a01 100644
--- a/TBF/Properties/AssemblyInfo.cs
+++ b/TBF/Properties/AssemblyInfo.cs
@@ -29,5 +29,5 @@ using System.Runtime.InteropServices;
 //      Build Number
 //      Revision
 //
-[assembly: AssemblyVersion("2.18.1085.0")]
-[assembly: AssemblyFileVersion("2.18.1085.0")]
+[assembly: AssemblyVersion("2.18.1086.0")]
+[assembly: AssemblyFileVersion("2.18.1086.0")]