``measurement``
======================
provides a graphic user interface for running the measurement.

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

Input parameters are:

* B_min: minimum of the measurement field (should be above -700 mT) 
* B_max: maximum of the measurement field (should be below 700 mT) 
* step: stepsize (in mT) in the field during the measurement   
* loops: number of measurement loops
* U_min: minimum of the plot range in V  
* U_max: maximum of the plot range in V 
* wait time: artificial additional wait time (s) after the current is set and before the diode is read out
* samples: number of measurements that are averaged for each datapoint  
* filename: name of the file in which the data is stored 


Available buttons:

* (re)start: starts the measurement	(always available)
* pause: pauses the measurement (only available during the measurement)
* select directory: selects the directory where the data is saved (always available)
* select calibration: choose electromagnet calibration file that is used for setting the current for the desired field steps
* save data: saves the data (only available after a measurment is finished)

The program saves the data in multiple files. 

All data points are stored consecutively in  ``all_data.txt``. The column std contains the standard deviation of the data N samples read from the balanced diode. The column direction is 1 as the field is increasing and the column loop contains the measurement loop::

	# B(mT)	 U (V)	 std (V)	 direction 	 loop 
	-400.0260	0.0213	0.1585	1.0000	1.0000
	-350.0421	0.0107	0.1596	1.0000	1.0000
	-300.0819	-0.0049	0.1572	1.0000	1.0000
	-249.9958	-0.0053	0.1591	1.0000	1.0000

The averaged result as displayed in the live plot is saved in  ``result.txt``::

	# B_up (mT)	 U_up (V) 	 Bdown (mT) 	 U_down (V) 
	-400.0260	0.0133	399.9500	0.0203
	-350.0421	0.0170	349.9728	0.0097
	-300.0819	0.0108	299.9068	0.0171
	-249.9958	0.0033	249.9820	0.0017

The files ``result_up.txt`` and ``result_down.txt`` are automatically generated and contain the field in the first column and the corresponding measurement value for each loop in the ensuing columns. The number of columuns corresponds thus to the number of set loops + 1::

	# B_down (mT)	 U_down (V) 
	399.9500	0.0195	0.0211
	349.9728	0.0108	0.0085
	299.9068	0.0103	0.0238
	249.9820	-0.0101	0.0135