diff --git a/ohmpi/hardware_system.py b/ohmpi/hardware_system.py
index f7365f636ed264156604a401743570eb2bb68d54..b76a7e23e21aecc99b548a542fdaf5155e5a2125 100644
--- a/ohmpi/hardware_system.py
+++ b/ohmpi/hardware_system.py
@@ -324,6 +324,7 @@ class OhmPiHardware:
         injection.start()
         readings.join()
         injection.join()
+        self.tx.polarity = 0
 
     def _vab_pulses(self, vab, lengths, sampling_rate, polarities=None, append=False):
         n_pulses = len(lengths)