diff --git a/hardware_components/ohmpi_card_3_15.py b/hardware_components/ohmpi_card_3_15.py
index c9398a49a409a138b2a4147e173a1980077f2bfe..f1d905f46a0d3e5270f39aaedf9c2a276dbc6a4c 100644
--- a/hardware_components/ohmpi_card_3_15.py
+++ b/hardware_components/ohmpi_card_3_15.py
@@ -2,6 +2,7 @@ import importlib
 from OhmPi.config import HARDWARE_CONFIG
 import adafruit_ads1x15.ads1115 as ads  # noqa
 from adafruit_ads1x15.analog_in import AnalogIn  # noqa
+from adafruit_ads1x15.ads1x15 import Mode  # noqa
 from adafruit_mcp230xx.mcp23008 import MCP23008  # noqa
 from digitalio import Direction  # noqa
 import minimalmodbus  # noqa
@@ -83,6 +84,7 @@ class Tx(TxAbstract):
         self._ads_current_address = 0x48
         self._ads_current = ads.ADS1115(self.controller.bus, gain=self.adc_gain, data_rate=860,
                                         address=self._ads_current_address)
+        self._ads_current.mode = Mode.CONTINUOUS
 
         # Relays for pulse polarity
         self.pin0 = self.mcp_board.get_pin(0)
@@ -216,6 +218,7 @@ class Rx(RxAbstract):
         self._ads_voltage_address = 0x49
         self._adc_gain = 2/3
         self._ads_voltage = ads.ADS1115(self.controller.bus, gain=self._adc_gain, data_rate=860, address=self._ads_voltage_address)
+        self._ads_voltage.mode = Mode.CONTINUOUS
         self._sampling_rate = kwargs.pop('sampling_rate', sampling_rate)
 
     @property
diff --git a/hardware_system.py b/hardware_system.py
index 3d7a90393a06056a3b3e165999e5d707b7003613..7852284d46f8b7254bb4056250013c7a3772665d 100644
--- a/hardware_system.py
+++ b/hardware_system.py
@@ -211,7 +211,7 @@ class OhmPiHardware:
             polarity = 1
         return vab, polarity, rab
 
-    def vab_square_wave(self, vab, cycle_length, sampling_rate, cycles=3, polarity=1, append=False):
+    def vab_square_wave(self, vab, cycle_length, sampling_rate=None, cycles=3, polarity=1, append=False):
         self.tx.polarity = polarity
         lengths = [cycle_length/2]*2*cycles
         self._vab_pulses(vab, lengths, sampling_rate, append=append)