Updates plot model in OhmPiHardware

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.sp) / self.readings[v, 3])/self.last_rho
+            return 100. * np.std(self.readings[v, 2] * self.readings[v, 4] / self.readings[v, 3]) / self.last_rho
         else:
             return np.nan
 
@@ -325,7 +325,7 @@ class OhmPiHardware:
         ax[2].set_ylabel('polarity [-]')
         v = self.readings[:, 2] != 0
         ax[3].plot(self.readings[:, 0], (self.readings[v, 2] * self.readings[v, 4] - self.sp) / self.readings[v, 3],
-                   '-m', marker='.', label='polarity')
+                   '-m', marker='.', label='R [ohm]')
         ax[3].set_ylabel('R [ohm]')
         fig.legend()
         if save_fig: