diff --git a/hardware/abstract_hardware.py b/hardware/abstract_hardware.py
index 881c9bea4f9d41724c637f7aa315675e02357ad7..23d20c4950d4470542290194ac8748f03bcd3409 100644
--- a/hardware/abstract_hardware.py
+++ b/hardware/abstract_hardware.py
@@ -17,7 +17,6 @@ class TxAbstract(ABC):
         if polarity is None:
             polarity = 0
         self._polarity = polarity
-        print(f'polarity: {polarity}')  # TODO: delete me
         inj_time = kwargs.pop('inj_time', 1.)
         self.exec_logger = kwargs.pop('exec_logger', None)
         if self.exec_logger is None:
diff --git a/measure.py b/measure.py
index 1c5a00b93621c209df3108a23a0dcb636aee0ff6..a05449005ae23bd94a8ce58a8ffbe7431fb7f7e1 100644
--- a/measure.py
+++ b/measure.py
@@ -58,7 +58,7 @@ class OhmPiHardware:
             self.tx.voltage_pulse(length=duration)
             self.tx_sync.clear()
 
-        def read_values(self, sampling_rate): # noqa
+        def read_values(self, data, sampling_rate): # noqa
             _readings = []
             self.tx_sync.wait()
             start_time = datetime.datetime.utcnow()
@@ -66,19 +66,20 @@ class OhmPiHardware:
                 lap = datetime.datetime.utcnow()
                 _readings.append([elapsed_seconds(start_time), self.tx.current, self.rx.voltage])
                 time.sleep(sampling_rate/1000.-elapsed_seconds(lap))
-            return np.array(_readings)
+            data = np.array(_readings)
 
         if sampling_rate is None:
             sampling_rate = RX_CONFIG['sampling_rate']
         if polarity is not None and polarity != self.tx.polarity:
             self.tx.polarity = polarity
         self.tx.voltage = vab
+        data = np.ndarray()
         injection = Thread(target=inject, args=[self], kwargs={'duration':length})
-        readings = Thread(target=read_values, args=[self], kwargs={'sampling_rate': sampling_rate})
+        readings = Thread(target=read_values, args=[self, data], kwargs={'sampling_rate': sampling_rate})
         # set gains automatically
         self.tx.adc_gain_auto()
         self.rx.adc_gain_auto()
-        data = readings.start()
+        readings.start()
         injection.start()
         readings.join()
         injection.join()