diff --git a/ohmpi/hardware_system.py b/ohmpi/hardware_system.py
index 2ec85791c81d522beb730d47156c5f5fab3e8d93..69c1577ad472c164562cd82c4a0ae82d85490a74 100644
--- a/ohmpi/hardware_system.py
+++ b/ohmpi/hardware_system.py
@@ -173,11 +173,11 @@ class OhmPiHardware:
                               self.rx.voltage])
             sample += 1
             sleep_time = self._start_time + datetime.timedelta(seconds=sample * sampling_rate / 1000) - lap
-            if sleep_time < 0.:
-                _readings.append([elapsed_seconds(self._start_time), self._pulse, self.tx.polarity, np.nan, np.nan])  # TODO:
+            if sleep_time.total_seconds() < 0.:
+                _readings.append([elapsed_seconds(self._start_time), self._pulse, self.tx.polarity, np.nan, np.nan])
                 sample += 1
             else:
-                time.sleep(np.max([0., sleep_time.total_seconds()]))  # TODO: set readings to nan if sleep time <0 and skip the sample (sample +=1)
+                time.sleep(np.max([0., sleep_time.total_seconds()]))
 
         self.exec_logger.warning(f'pulse {self._pulse}: elapsed time {(lap-self._start_time).total_seconds()} s')  # TODO: Set to debug level
         self.exec_logger.warning(f'pulse {self._pulse}: total samples {len(_readings)}')  # TODO: Set to debug level