Update README.rst

Author: Dennis-van-Gils

README.rst

@@ -28,3 +28,8 @@ installed already in your Python environment.
 Other depencies you'll need for this demo can be installed by running::
 
   pip install -r requirements.txt
+
+PyQtGraph performance
+=====================
+
+The specific version of PyQtGraph can have major influence on the timing stability of the DAQ routine, visible as a fluctuating time stamp in a recorded log file. I observe that ``PyQtGraph==0.11`` leads to a great timing stability of +/- 1 ms, whereas ``0.12.4`` and ``0.13.1`` are very detrimental to the stability with values of +/- 10 ms. The reason for this is still unknown. I have to investigate further.