Modifies the way last_dev is computed in hardware system

ohmpi/hardware_components/dummy_ctl.py

@@ -8,4 +8,4 @@ class Ctl(CtlAbstract):
     def __init__(self, **kwargs):
         kwargs.update({'board_name': os.path.basename(__file__).rstrip('.py')})
         super().__init__(**kwargs)
-        self.bus = None
+        self.connections = None

ohmpi/hardware_components/dummy_tx.py

-from ohmpi.ohmpi.config import HARDWARE_CONFIG
+from ohmpi.config import HARDWARE_CONFIG
 import time
 import os
 import numpy as np

ohmpi/hardware_system.py

@@ -215,7 +215,7 @@ class OhmPiHardware:
     def last_dev(self):
         if len(self.readings) > 1:
             v = self.readings[:, 2] != 0  # exclude sample where the is no injection
-            return 100. * np.std(self.readings[v, 2] * self.readings[v, 4] / self.readings[v, 3]) / self.last_rho
+            return 100. * np.std(self.readings[v, 2] * (self.readings[v, 4] - self.sp) / self.readings[v, 3]) / self.last_rho
         else:
             return np.nan