diff --git a/test_comport_writer/test_writer.py b/test_comport_writer/test_writer.py
index dda79f0..b6bd6ee 100644
--- a/test_comport_writer/test_writer.py
+++ b/test_comport_writer/test_writer.py
@@ -74,13 +74,16 @@ class ComPortTestWriter:
     
     def generate_scales_data(self) -> str:
         """Generate simulated scales data"""
-        # Simulate scales value fluctuating slightly
-        variation = random.uniform(-0.1, 0.1)
-        self.current_scales_value += variation
-        
-        # Keep within bounds
+        # Step through the range and reverse at each end
+        if not hasattr(self, '_direction'):
+            self._direction = 1
+        step = random.uniform(SCALES_INCREMENT * 0.8, SCALES_INCREMENT * 1.2)
+        self.current_scales_value += step * self._direction
+        if self.current_scales_value >= SCALES_MAX:
+            self._direction = -1
+        elif self.current_scales_value <= SCALES_MIN:
+            self._direction = 1
         self.current_scales_value = max(SCALES_MIN, min(SCALES_MAX, self.current_scales_value))
-        
         return f"{self.current_scales_value:.2f} kg"
     
     def generate_counter_data(self) -> str: