diff --git a/ohmpi/hardware_system.py b/ohmpi/hardware_system.py
index 1f9843cca741209fa2a1a97b43d9ac2565c15bc5..71fd2b96961833493f5bbb39d47a0a67ea2603fc 100644
--- a/ohmpi/hardware_system.py
+++ b/ohmpi/hardware_system.py
@@ -431,8 +431,8 @@ class OhmPiHardware:
             while (k < n_steps) and (diff_vab > diff_vab_lim):
                 vabs = []
                 self._vab_pulses(vab_list[k], sampling_rate=self.rx.sampling_rate, durations=[0.2, 0.2], polarities=[1, -1])
-                for pol in range(2):
-                    v = np.where((self.readings[:, 0] > delay) & (self.readings[:, 2] != 0) & (self.readings[:, pol]))[0]  # NOTE : discard data aquired in the first x ms
+                for pulse in range(2):
+                    v = np.where((self.readings[:, 0] > delay) & (self.readings[:, 2] != 0) & (self.readings[:, 1]==pulse))[0]  # NOTE : discard data aquired in the first x ms
                     iab = self.readings[v, 3]/1000.
                     vmn = np.abs(self.readings[v, 4]/1000. * self.readings[v, 2])
                     new_vab = self._find_vab(vab_list[k], iab, vmn, )