diff --git a/mainwindow.cpp b/mainwindow.cpp
--- a/mainwindow.cpp
+++ b/mainwindow.cpp
@@ -32,6 +32,9 @@ MainWindow::MainWindow(QWidget *parent) 
     QObject::connect(&(this->serialPort), &QSerialPort::readyRead,
                      this, &MainWindow::onDataReady);
 
+    QObject::connect(ui->spNumOfSamples, SELECT<int>::OVERLOAD_OF(&QSpinBox::valueChanged),
+                     this, &MainWindow::onNumOfSamplesChanged);
+
     // init port signals
     QObject::connect(&(this->serialPort), SIGNAL(error(QSerialPort::SerialPortError)),
                      this, SLOT(onPortError(QSerialPort::SerialPortError)));
@@ -41,7 +44,7 @@ MainWindow::MainWindow(QWidget *parent) 
     ui->cbBaudRate->setCurrentIndex(ui->cbBaudRate->findText("9600"));
 
     // init plot
-    numOfSamples = 100;
+    numOfSamples = ui->spNumOfSamples->value();
     dataArray.resize(numOfSamples);
     dataX.resize(numOfSamples);
     for (int i = 0; i < dataX.size(); i++)
@@ -200,3 +203,25 @@ void MainWindow::addData(double data)
     curve.setSamples(dataX, dataArray);
     ui->plot->replot();
 }
+
+void MainWindow::onNumOfSamplesChanged(int value)
+{
+    int oldNum = this->numOfSamples;
+    numOfSamples = value;
+
+    // resize data arrays
+    if (numOfSamples < oldNum)
+    {
+        dataX.resize(numOfSamples);
+        dataArray.remove(0, oldNum - numOfSamples);
+    }
+    else if(numOfSamples > oldNum)
+    {
+        dataX.resize(numOfSamples);
+        for (int i = oldNum; i < numOfSamples; i++)
+        {
+            dataX[i] = i;
+            dataArray.prepend(0);
+        }
+    }
+}
diff --git a/mainwindow.h b/mainwindow.h
--- a/mainwindow.h
+++ b/mainwindow.h
@@ -40,6 +40,8 @@ private slots:
     void onDataReady();
     void onPortError(QSerialPort::SerialPortError error);
 
+    void onNumOfSamplesChanged(int value);
+
 signals:
     void portToggled(bool open);
 };
diff --git a/mainwindow.ui b/mainwindow.ui
--- a/mainwindow.ui
+++ b/mainwindow.ui
@@ -6,7 +6,7 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>652</width>
+    <width>653</width>
     <height>534</height>
    </rect>
   </property>
@@ -326,10 +326,73 @@
         </item>
        </layout>
       </widget>
-      <widget class="QWidget" name="tab_2">
+      <widget class="QWidget" name="tabPlot">
        <attribute name="title">
-        <string>Tab 2</string>
+        <string>Plot</string>
        </attribute>
+       <layout class="QHBoxLayout" name="horizontalLayout_4">
+        <item>
+         <spacer name="horizontalSpacer_2">
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+          <property name="sizeHint" stdset="0">
+           <size>
+            <width>370</width>
+            <height>20</height>
+           </size>
+          </property>
+         </spacer>
+        </item>
+        <item>
+         <widget class="Line" name="line">
+          <property name="orientation">
+           <enum>Qt::Vertical</enum>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <layout class="QVBoxLayout" name="verticalLayout_8">
+          <item>
+           <layout class="QHBoxLayout" name="horizontalLayout_3">
+            <item>
+             <widget class="QLabel" name="label_3">
+              <property name="text">
+               <string>Number Of Samples:</string>
+              </property>
+             </widget>
+            </item>
+            <item>
+             <widget class="QSpinBox" name="spNumOfSamples">
+              <property name="minimum">
+               <number>2</number>
+              </property>
+              <property name="maximum">
+               <number>10000</number>
+              </property>
+              <property name="value">
+               <number>1000</number>
+              </property>
+             </widget>
+            </item>
+           </layout>
+          </item>
+          <item>
+           <spacer name="verticalSpacer_3">
+            <property name="orientation">
+             <enum>Qt::Vertical</enum>
+            </property>
+            <property name="sizeHint" stdset="0">
+             <size>
+              <width>20</width>
+              <height>40</height>
+             </size>
+            </property>
+           </spacer>
+          </item>
+         </layout>
+        </item>
+       </layout>
       </widget>
      </widget>
     </item>
@@ -340,8 +403,8 @@
     <rect>
      <x>0</x>
      <y>0</y>
-     <width>652</width>
-     <height>20</height>
+     <width>653</width>
+     <height>23</height>
     </rect>
    </property>
    <widget class="QMenu" name="menuFile">