diff --git a/measure.py b/measure.py
index 64aa9a11112e0d221c2e81a22177fe8db1f01c30..ea0b50f827affeccd02a9e69d90f6640062efb01 100644
--- a/measure.py
+++ b/measure.py
@@ -62,9 +62,7 @@ class OhmPiHardware:
     def _read_values(self, sampling_rate, append=False):  # noqa
         if not append:
             self._clear_values()
-            _readings = []
-        else:
-            _readings = self.readings.tolist()
+        _readings = []
         sample = 0
         self.tx_sync.wait()
         start_time = datetime.datetime.utcnow()
@@ -74,7 +72,7 @@ class OhmPiHardware:
             sample+=1
             sleep_time = start_time + datetime.timedelta(seconds = sample * sampling_rate / 1000) - lap
             time.sleep(np.min([0, np.abs(sleep_time.total_seconds())]))
-        self.readings = np.array(_readings)
+        self.readings = np.hstack([self.readings, np.array(_readings)])
 
     def _compute_tx_volt(self, best_tx_injtime=0.1, strategy='vmax', tx_volt=5,
                          vab_max=voltage_max, vmn_min=voltage_min):
@@ -157,7 +155,7 @@ class OhmPiHardware:
         self.tx.polarity = polarity
         lengths = [cycle_length/2]*2*cycles  # TODO: delete me
         print(f'vab_square_wave lengths: {lengths}')
-        self._vab_pulses(vab, lengths, sampling_rate, append)
+        self._vab_pulses(vab, lengths, sampling_rate, append=append)
 
     def _vab_pulse(self, vab, length, sampling_rate=None, polarity=None, append=False):
         """ Gets VMN and IAB from a single voltage pulse
diff --git a/test_measure_with_ohmpi_card_3_15.py b/test_measure_with_ohmpi_card_3_15.py
index 73fb9e515a86018ee1a4075208be47e4d743a2be..966140bf771b730928f0d21823844086354704d4 100644
--- a/test_measure_with_ohmpi_card_3_15.py
+++ b/test_measure_with_ohmpi_card_3_15.py
@@ -14,7 +14,7 @@ print(f'sampling rate: {k.rx.sampling_rate:.1f} ms, mean sample spacing: {np.mea
 
 # Test #2:
 print('\n\nTesting vab_square_wave')
-k.vab_square_wave(vab=12, length=1., sampling_rate=k.rx.sampling_rate, cycles=3)
+k.vab_square_wave(vab=12, cycle_length=2., sampling_rate=k.rx.sampling_rate, cycles=3)
 r = k.readings[:,2]/k.readings[:,1]
 print(f'Mean resistance: {np.mean(r):.3f} Ohms, Dev. {100*np.std(r)/np.mean(r):.1f} %')
 print(f'sampling rate: {k.rx.sampling_rate:.1f} ms, mean sample spacing: {np.mean(np.diff(k.readings[:,0]))*1000.:.1f} ms')