diff --git a/ohmpi/hardware_system.py b/ohmpi/hardware_system.py
index 1996b5e91838bdb83e654aa54a3ca9f236a0552a..38fc63fa4bcabe52ac34fe0b3cf2605a77575eaf 100644
--- a/ohmpi/hardware_system.py
+++ b/ohmpi/hardware_system.py
@@ -207,7 +207,7 @@ class OhmPiHardware:
         v = self.readings[:, 2] != 0
         if len(v) > 1:
             # return np.mean(np.abs(self.readings[v, 4] - self.sp) / self.readings[v, 3])
-            return np.mean((self.readings[v, 2] * self.readings[v, 4] - self.sp) / self.readings[v, 3])
+            return np.mean(self.readings[v, 2] * (self.readings[v, 4] - self.sp) / self.readings[v, 3])
         else:
             return np.nan
 
diff --git a/ohmpi/ohmpi.py b/ohmpi/ohmpi.py
index 725bc99defa963a66bca629751c5b6f19fc69154..54e3b23cd30dd0eddd7738d24d513b26397e3e96 100644
--- a/ohmpi/ohmpi.py
+++ b/ohmpi/ohmpi.py
@@ -453,7 +453,7 @@ class OhmPi(object):
         tx_volt = float(tx_volt)
         bypass_check = kwargs['bypass_check'] if 'bypass_check' in kwargs.keys() else False
         if self.switch_mux_on(quad, bypass_check=bypass_check, cmd_id=cmd_id):
-            self._hw.vab_square_wave(tx_volt, cycle_duration=injection_duration*2, cycles=nb_stack)
+            self._hw.vab_square_wave(tx_volt, cycle_duration=injection_duration*2, cycles=nb_stack, duty_cycle=kwargs.pop('duty_cycle', 1.))
             if 'delay' in kwargs.keys():
                 delay = kwargs['delay']
             else: