``diode_calibration``
======================
This program provides a graphic user interface which allows to calibrate the voltage vs. polarization.  

.. image:: _static/diode_calibration.jpg
  :alt: screenshot of the diode_calibration gui
  :width: 600
  

Input parameters are:

* current angle: angle of the waveplate read from the scale
* angle step: angle increment to the next datapoint 
* maximum of the measurement field (should be below 700 mT) 
* samples: number of measurements that are averaged for each datapoint  
* filename: name of the file in which the data is stored 


Available buttons:

* add point: adds a measurement point and updates the plot 
* clear last point: removes the last point and updates the plot 
* clear all reload: clears all data
* fit line: fits a linear model to the data
* select path: selects the directory where the data is saved 
* save data: saves the data

The program saves the data in the following format in ``diode_calibration.txt``. The idea is to change the waveplate angle by 1° and then add a point. If you change the waveplate angle by 1° the polarization angle of the light changes by 2°. The third column contains the standard deviation of the N samples measured::

	# angle (°)	 diode voltage U (V)	 diode std
	0.00000	0.00888	0.15983
	2.00000	0.00983	0.16038
	4.00000	0.01205	0.16074
	6.00000	0.01191	0.16054

Here an image of the waveplate mount with the rough scale and the fine Vernier scale.

.. image:: _static/waveplate_1.jpg
  :alt: picture of the waveplate mount
  :width: 200