Repair and add SignalR

RTD_8chanels_board.cs

@@ -41,6 +41,11 @@ namespace Libs_SequentMicrosystems
                 throw new IOException($"Fail to communicate with the RTD card with message: \"{e.Message}\"");
             }
 
+            if (val < 0)
+            {
+                val = 0;
+            }
+
             return val;
         }