diff --git a/ohmpi/hardware_system.py b/ohmpi/hardware_system.py
index d932cc994ba5470f2636d1a0c1da6a684942120e..157b5ea7f8821b4d16056a022642f1dee2fc6892 100644
--- a/ohmpi/hardware_system.py
+++ b/ohmpi/hardware_system.py
@@ -172,7 +172,7 @@ class OhmPiHardware:
             _readings.append([elapsed_seconds(self._start_time), self._pulse, self.tx.polarity, self.tx.current,
                               self.rx.voltage])
             sample += 1
-            sleep_time = self._start_time + datetime.timedelta(seconds=sample / sampling_rate * 1000) - lap
+            sleep_time = self._start_time + datetime.timedelta(seconds=sample / sampling_rate) - lap
             if sleep_time.total_seconds() < 0.:
                 _readings.append([elapsed_seconds(self._start_time), self._pulse, self.tx.polarity, np.nan, np.nan])
                 sample += 1