diff --git a/ohmpi/hardware_components/ohmpi_card_3_15.py b/ohmpi/hardware_components/ohmpi_card_3_15.py
index 20c93a1016c40e072d84543896a192b23ed70d6d..34d94a9aaf804e96723158b4a9d0847660fa5b0f 100644
--- a/ohmpi/hardware_components/ohmpi_card_3_15.py
+++ b/ohmpi/hardware_components/ohmpi_card_3_15.py
@@ -256,6 +256,6 @@ class Rx(RxAbstract):
         """ Gets the voltage VMN in Volts
         """
         self.exec_logger.event(f'{self.board_name}\trx_voltage\tbegin\t{datetime.datetime.utcnow()}')
-        u = -AnalogIn(self._ads_voltage, ads.P0, ads.P1).voltage * self._coef_p2 * 1000. - self._bias  # TODO: check if it should be negated
+        u = -AnalogIn(self._ads_voltage, ads.P0, ads.P1).voltage * self._coef_p2 * 1000. + self._bias  # TODO: check if it should be negated
         self.exec_logger.event(f'{self.board_name}\trx_voltage\tend\t{datetime.datetime.utcnow()}')
         return u
diff --git a/ohmpi/hardware_system.py b/ohmpi/hardware_system.py
index 262d98415214ea762377e04240d7d500f231457f..eb9491a7cd0bfbdfc182baf5d7ed842a83394b80 100644
--- a/ohmpi/hardware_system.py
+++ b/ohmpi/hardware_system.py
@@ -323,7 +323,8 @@ class OhmPiHardware:
         plt.show()
 
     def calibrate_rx_bias(self):
-        self.rx._bias = (np.mean(self.readings[self.readings[:, 2] == 1, 4]) + np.mean(self.readings[self.readings[:, 2] == -1, 4])) / 2.
+        self.rx._bias = (np.mean(self.readings[self.readings[:, 2] == 1, 4])
+                         + np.mean(self.readings[self.readings[:, 2] == -1, 4])) / 2.
 
     def vab_square_wave(self, vab, cycle_duration, sampling_rate=None, cycles=3, polarity=1, append=False):
         self.exec_logger.event(f'OhmPiHardware\tvab_square_wave\tbegin\t{datetime.datetime.utcnow()}')