Fixes bug in run_measurement

ohmpi/ohmpi.py

@@ -460,7 +460,7 @@ class OhmPi(object):
                 delay = 0.
             x = np.where((self._hw.readings[:, 0] >= delay) & (self._hw.readings[:, 2] != 0))
             R = np.mean(self._hw.readings[x, 2]*self._hw.readings[x, 4])/np.median(self._hw.readings[x, 3])
-            R_std = 100. * np.std(self._hw.readings[x, 2] * (self._hw.readings[x, 4] - self.sp) / self._hw.readings[x, 3])/R
+            R_std = 100. * np.std(self._hw.readings[x, 2] * (self._hw.readings[x, 4] - self._hw.sp) / self._hw.readings[x, 3])/R
             d = {
                 "time": datetime.now().isoformat(),
                 "A": quad[0],