magdynlab

This software is developed for the automation and control of the experiments of the Magnetization Dynamics Laboratory at the Brazilian Center for Physics Research (CBPF), Rio de Janeiro, Brazil.

The main purpose of this software is to be easy to use. Anyone with a minimal python programming skill should be able to easily create new experiment routines.

How to use:

This software uses three layers of abstraction to simplify the creation of experiment routines

1.- Instruments

This layer handles the complexity of communication with the physical instruments

For example, for setting out the output current of a power source KEPCO instrument, instead of doing:

import visa
 
ResourceName = 'GPIB0::6::INSTR'

rm  = visa.ResourceManager()
KepcoVI = open_resource(ResourceName)
KepcoVI.write_termination = KepcoVI.LF
KepcoVI.write('*CLS')
KepcoVI.write('*RST')
KepcoVI.write('OUTPUT ON')
KepcoVI.write('FUNC:MODE CURR')
KepcoVI.write('VOLT 20') #  Protection voltage 20 Volts

current_value = 10  # 10 Amps
KepcoVI.write('CURR %0.4f' % current_value)

the use of a magdynlab.instrument hides the SCPI codes and make the python code easier to write, read and understand

import magdynlab.instruments
 
PowerSource = magdynlab.instruments.KEPCO_BOP(GPIB_Address=6)
PowerSource.CurrentMode()
PowerSource.voltage = 20 #  Protection voltage 20 Volts

PowerSource.current = 10  # 10 Amps

2.- Controlers

This layer hides complex software routines using the instruments

For example, to set a magnetic field using a coil connected to a power source, the following code:

import magdynlab.instruments
import time
 
PowerSource = magdynlab.instruments.KEPCO_BOP(GPIB_Address=6)
PowerSource.CurrentMode()
PowerSource.voltage = 20  # Protection voltage 20 Volts
field_per_amp = 15.87  # Coil calibration in Oe/A
max_rate = 30.0  # Max field rate in Oe/s

field_to_set = 300.0 # 300 Oe
for i in range(50):  # ramp to the field using 50 steps (simple implementation)
    time_per_step = (field_to_set / max_rate) / 50
    time.sleep(time_per_step)
    PowerSource.current = (i * field_to_set / 50) / field_per_amp

is simplified using a magdynlab.controler

import magdynlab.instruments
import magdynlab.controlers
 
PowerSource = magdynlab.instruments.KEPCO_BOP(GPIB_Address=6)
FieldControler = magdynlab.controlers.FieldControler(PowerSource)
FieldControler.HperOut = 15.87  # Coil calibration in Oe/A
FieldControler.MaxHRate = 30.0  # Max field rate in Oe/s

field_to_set = 300.0 # 300 Oe
FieldControler.setField(field_to_set)

3.- Experiments

This layer is used to implement experiment routines

For example, to measure a magnetization curve in a VSM the following code can be used:

import numpy
import magdynlab.instruments
import magdynlab.controlers
import magdynlab.data_types
 
PowerSource = magdynlab.instruments.KEPCO_BOP(GPIB_Address=6)
LockIn = magdynlab.instruments.SRS_SR830()

FC = magdynlab.controlers.FieldControler(PowerSource)
VC = magdynlab.controlers.LockIn_Mag_Controler(LockIn)
Data = magdynlab.data_types.Data2D()

FC.HperOut = 15.87  # Coil calibration in Oe/A
FC.MaxHRate = 30.0  # Max field rate in Oe/s
VC.emu_per_V = 18.7  # Sensing coils sensibility in emu/V

def Measure_MxH(field_pts, file_name):
    Data.reset()
    for h in field_pts:
        # Really easy to read loop! :-)
        FC.setField(h)
        m, sm = VC.getMagnetization()
        Data.addPoint(h, m)
    SaveData(file_name)
    FC.TurnOff()

then, making a real measurement is as simple as:

r1 = numpy.linspace(-300, 300, 101)
field_pts = numpy.r_[r1, r1[::-1]]  # 101 points from -300 Oe to 300 Oe
                                    # and the same in the oposite direction
Measure_MxH(field_pts, 'my_output_file.txt')