diff --git a/hardware_system.py b/hardware_system.py
index 48991f5e87c95109d2cf9c068a76f155967e57e8..e4401772250c4a56acbc12828e05c4a10af24386 100644
--- a/hardware_system.py
+++ b/hardware_system.py
@@ -245,7 +245,7 @@ class OhmPiHardware:
         if self.tx.pwr.voltage_adjustable:
             self.tx.pwr.voltage = vab
         else:
-            vab = self.tx.voltage
+            vab = self.tx.pwr.voltage
         injection = Thread(target=self._inject, kwargs={'duration':length})
         readings = Thread(target=self._read_values, kwargs={'sampling_rate': sampling_rate, 'append': append})
         # set gains automatically