diff --git a/ohmpi/hardware_components/ohmpi_card_3_15.py b/ohmpi/hardware_components/ohmpi_card_3_15.py
index 94f161e67b88c712d325672c7387d246dd4ee2ba..fc480edf7234e6f96887115126664acff39ffec7 100644
--- a/ohmpi/hardware_components/ohmpi_card_3_15.py
+++ b/ohmpi/hardware_components/ohmpi_card_3_15.py
@@ -254,6 +254,6 @@ 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.
+        u = AnalogIn(self._ads_voltage, ads.P0, ads.P1).voltage * self._coef_p2 * 1000.  # TODO:  check if it should be negative
         self.exec_logger.event(f'{self.board_name}\trx_voltage\tend\t{datetime.datetime.utcnow()}')
         return u