diff --git a/@MyNewportUsbComm/MyNewportUsbComm.m b/@MyNewportUsbComm/MyNewportUsbComm.m
index 68e887e..369b671 100644
--- a/@MyNewportUsbComm/MyNewportUsbComm.m
+++ b/@MyNewportUsbComm/MyNewportUsbComm.m
@@ -1,82 +1,101 @@
 classdef MyNewportUsbComm < MySingleton
     
     properties (GetAccess = public, SetAccess = private)
-        isbusy = false  % driver in use 
+        
+        % Driver in use
+        isbusy = false
+        
+        % QueryData objects are stored in order to ensure that these 
+        % objects are not deleted before the Newport driver finishes 
+        % operations on them
+        QueryRecord = {}
     end
     
     properties (Access = public)
-        Usb % Instance of Newport.USBComm.USB class 
+        
+        % An instance of Newport.USBComm.USB class 
+        Usb
+    end
+    
+    properties (Access = private)
+        query_record_max_length = 1e4
     end
     
     methods(Access = private)
         
         % The constructor of a singleton class should only be invoked from
         % the instance method.
         function this = MyNewportUsbComm()
             disp(['Creating a new instance of ' class(this)])
             loadLib(this);
         end
     end
     
     methods(Access = public)
         
         % Load dll
         function loadLib(this)
             dll_path = which('UsbDllWrap.dll');
             if isempty(dll_path)
                 error(['UsbDllWrap.dll is not found. This library ',...
                     'is a part of Newport USB driver and needs ',...
                     'to be present on Matlab path.'])
             end
             NetAsm = NET.addAssembly(dll_path);
             
             % Create an instance of Newport.USBComm.USB class
             Type = GetType(NetAsm.AssemblyHandle,'Newport.USBComm.USB');
             this.Usb = System.Activator.CreateInstance(Type);
         end
         
         function str = query(this, addr, cmd)
             
             % Check if the driver is already being used by another process.
             % A race condition with various strange consequences is 
             % potentially possible if it is.
             if this.isbusy
                 warning('NewportUsbComm is already in use')
             end
             
             this.isbusy = true;
             
             % Send query using QueryData buffer. A new buffer needs to be
             % created every time to ensure the absence of interference 
             % between different queries.
             QueryData = System.Text.StringBuilder(64);
             
             stat = Query(this.Usb, addr, cmd, QueryData);
             
             if stat == 0
                 str = char(ToString(QueryData));
             else
                 str = '';
                 warning('Query to Newport usb driver was unsuccessful.');
             end
             
+            this.QueryRecord = [this.QueryRecord, {QueryData}];
+            ml = this.query_record_max_length;
+            if length(this.QueryRecord) > ml
+                this.QueryRecord = this.QueryRecord(end-ml+1:end);
+            end
+            
             this.isbusy = false;
         end
     end
    
     methods(Static)
         
         % Concrete implementation of the singleton constructor.
         function this = instance()
             persistent UniqueInstance
 
             if isempty(UniqueInstance) || ~isvalid(UniqueInstance)
                 this = MyNewportUsbComm();
                 UniqueInstance = this;
             else
                 this = UniqueInstance;
             end
         end
     end
 end