diff --git a/gui/main.py b/gui/main.py
index f98f4cb..b741194 100644
--- a/gui/main.py
+++ b/gui/main.py
@@ -6,6 +6,11 @@ from PyQt6.QtWidgets import (QApplication, QMainWindow, QVBoxLayout, QHBoxLayout
                             QGroupBox, QStatusBar, QMessageBox, QCheckBox)
 from PyQt6.QtCore import QTimer, Qt
 from PyQt6.QtGui import QFont
+import matplotlib.pyplot as plt
+from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
+from matplotlib.figure import Figure
+import datetime
+from collections import deque
 
 class PHControllerGUI(QMainWindow):
     def __init__(self):
@@ -13,7 +18,7 @@ class PHControllerGUI(QMainWindow):
         self.serial_connection = None
         self.updating_tube_combo = False  # Flag to prevent recursive tube commands
         self.setWindowTitle("Arduino pH Controller")
-        self.setGeometry(100, 100, 600, 400)
+        self.setGeometry(100, 100, 900, 800)  # Larger window for plot
         
         # Central Widget
         central_widget = QWidget()
@@ -136,6 +141,30 @@ class PHControllerGUI(QMainWindow):
         main_layout.addWidget(status_group)
         main_layout.addWidget(control_group)
         
+        # pH Plot Group
+        plot_group = QGroupBox("pH-Verlauf")
+        plot_layout = QVBoxLayout()
+        
+        # Plot controls
+        plot_controls_layout = QHBoxLayout()
+        self.clear_plot_btn = QPushButton("Diagramm löschen")
+        self.clear_plot_btn.clicked.connect(self.clear_ph_plot)
+        self.plot_enabled_checkbox = QCheckBox("pH-Aufzeichnung")
+        self.plot_enabled_checkbox.setChecked(True)
+        
+        plot_controls_layout.addWidget(self.plot_enabled_checkbox)
+        plot_controls_layout.addWidget(self.clear_plot_btn)
+        plot_controls_layout.addStretch()
+        
+        # pH Plot Widget
+        self.ph_plot = PHPlotWidget()
+        
+        plot_layout.addLayout(plot_controls_layout)
+        plot_layout.addWidget(self.ph_plot)
+        plot_group.setLayout(plot_layout)
+        
+        main_layout.addWidget(plot_group)
+        
         # Status Bar
         self.status_bar = QStatusBar()
         self.setStatusBar(self.status_bar)
@@ -260,6 +289,8 @@ class PHControllerGUI(QMainWindow):
         self.auto_dose_btn.setEnabled(enabled)
         self.volume_spin.setEnabled(enabled)
         self.reset_volume_checkbox.setEnabled(enabled)
+        self.clear_plot_btn.setEnabled(enabled)
+        self.plot_enabled_checkbox.setEnabled(enabled)
     
     def send_command(self, command):
         print(command)
@@ -432,6 +463,9 @@ class PHControllerGUI(QMainWindow):
                         try:
                             ph_value = float(data[1:])
                             self.ph_label.setText(f"pH: {ph_value:.2f}")
+                            # Add to plot if recording is enabled
+                            if self.plot_enabled_checkbox.isChecked():
+                                self.ph_plot.add_ph_value(ph_value)
                         except ValueError:
                             pass
                     elif data.startswith('P'):  # Pump status
@@ -488,6 +522,119 @@ class PHControllerGUI(QMainWindow):
         self.close_connection()
         event.accept()
 
+    def clear_ph_plot(self):
+        """Clear the pH plot data"""
+        self.ph_plot.clear_data()
+        self.status_bar.showMessage("pH-Diagramm gelöscht")
+    
+class PHPlotWidget(QWidget):
+    def __init__(self):
+        super().__init__()
+        self.figure = Figure(figsize=(8, 4))
+        self.canvas = FigureCanvas(self.figure)
+        self.ax = self.figure.add_subplot(111)
+        
+        # Data storage (keep last 300 points = 10 minutes at 2-second intervals)
+        self.times = deque(maxlen=300)
+        self.ph_values = deque(maxlen=300)
+        self.start_time = None  # Track when recording started
+        
+        # Setup plot
+        self.ax.set_xlabel('Zeit')
+        self.ax.set_ylabel('pH-Wert')
+        self.ax.set_title('pH-Verlauf')
+        self.ax.grid(True, alpha=0.3)
+        self.ax.set_ylim(0, 14)  # pH range 0-14
+        
+        # Layout
+        layout = QVBoxLayout()
+        layout.addWidget(self.canvas)
+        self.setLayout(layout)
+        
+        # Plot line
+        self.line, = self.ax.plot([], [], 'b-', linewidth=2, label='pH-Wert')
+        self.ax.legend()
+        
+        # Initial draw
+        self.canvas.draw()
+    
+    def add_ph_value(self, ph_value):
+        """Add new pH value with current timestamp"""
+        current_time = datetime.datetime.now()
+        
+        # Set start time on first value
+        if self.start_time is None:
+            self.start_time = current_time
+        
+        # Calculate relative time in seconds
+        relative_time = (current_time - self.start_time).total_seconds()
+        
+        self.times.append(relative_time)
+        self.ph_values.append(ph_value)
+        self.update_plot()
+    
+    def update_plot(self):
+        """Update the plot with current data"""
+        if len(self.times) > 0 and len(self.ph_values) > 0:
+            # Update line data
+            self.line.set_data(self.times, self.ph_values)
+            
+            # Auto-scale x-axis to show recent data
+            if len(self.times) > 1:
+                self.ax.set_xlim(min(self.times), max(self.times))
+            
+            # Auto-scale y-axis around data with some margin
+            if len(self.ph_values) > 0:
+                min_ph = min(self.ph_values)
+                max_ph = max(self.ph_values)
+                margin = 0.5
+                self.ax.set_ylim(max(0, min_ph - margin), min(14, max_ph + margin))
+            
+            # Format x-axis for time display (seconds/minutes/hours)
+            self.format_time_axis()
+            
+            # Redraw
+            self.canvas.draw()
+    
+    def format_time_axis(self):
+        """Format the x-axis to show time in appropriate units"""
+        if len(self.times) == 0:
+            return
+            
+        max_time = max(self.times)
+        
+        if max_time < 120:  # Less than 2 minutes - show seconds
+            self.ax.set_xlabel('Zeit (Sekunden)')
+            # No need to change tick formatting for seconds
+        elif max_time < 7200:  # Less than 2 hours - show minutes
+            self.ax.set_xlabel('Zeit (Minuten)')
+            # Convert tick labels to minutes
+            import matplotlib.ticker as ticker
+            def format_minutes(x, pos):
+                return f'{x/60:.1f}'
+            self.ax.xaxis.set_major_formatter(ticker.FuncFormatter(format_minutes))
+        else:  # Show hours
+            self.ax.set_xlabel('Zeit (Stunden)')
+            # Convert tick labels to hours
+            import matplotlib.ticker as ticker
+            def format_hours(x, pos):
+                return f'{x/3600:.1f}'
+            self.ax.xaxis.set_major_formatter(ticker.FuncFormatter(format_hours))
+    
+    def clear_data(self):
+        """Clear all data points"""
+        self.times.clear()
+        self.ph_values.clear()
+        self.start_time = None  # Reset start time
+        self.line.set_data([], [])
+        self.ax.set_xlim(0, 1)
+        self.ax.set_ylim(0, 14)
+        self.ax.set_xlabel('Zeit')  # Reset to default label
+        # Reset tick formatter to default
+        import matplotlib.ticker as ticker
+        self.ax.xaxis.set_major_formatter(ticker.ScalarFormatter())
+        self.canvas.draw()
+
 def main():
     app = QApplication(sys.argv)
     window = PHControllerGUI()
diff --git a/requirements.txt b/requirements.txt
index e0d5c5c..7030bdf 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1,4 @@
-PyQt6==6.9.0
-pyserial==3.5
\ No newline at end of file
+PyQt6==6.7.0
+pyserial==3.5
+matplotlib==3.7.2
+numpy<2.0.0
\ No newline at end of file