""" Use the Keithley 6220 and 2182A to sweep IV curves for different

magnetic fields. The function will save a plot each IV curve as it runs.

fieldLim/biasLim should be an array with 3 elements [start, stop, step]

given in Tesla/Volts.

Be sure to optimize the nanovoltmeter range. Setting it to 'auto'

is quite slow.

If you are sourcing current and measuring voltage, set the cvAmp and

current to voltage resistor to 1.0

To run: measurement = keithleypair_IV_Var.IV_MagField()

measurement.run(biasLim, fieldLim, ...)

End early with 'q'. Do NOT close the plot before ending

the sweep. """

def __init__(self, filename = 'iv-DAQgate_{0:.0f}'.format(time.time())):

""" opens a file for the experiment. this means you have to start a new instance

of the class each time you want a new file. strange. maybe ok? """

self.filename = filename

self.file = open(filename+'.dat','a')

def run_simple(biasLim, fieldLim, gate = 0.0, ivAvg = 1,

cvResistor = 10.0, cvAmp = -1e-6, gateAmp = 9.1788,

srcDelay = 0.01, fieldDelay = 2.0,

nplc = 1, nvmRange = 0.1):

""" Runs the actual experiment. Can be called directly if plotting is

not needed. """

tools.write_log('iv_magField', locals(), filename+'.log')

biasBuffer = tools.get_buffer_size(biasLim[0], biasLim[1], biasLim[2])

bias = np.linspace(biasLim[0], biasLim[1], biasBuffer)

np.savetxt(file, [np.insert(bias, 0, 0.0)], fmt = '%+.6e', delimiter = '\t')

fieldBuffer = tools.get_buffer_size(fieldLim[0], fieldLim[1], fieldLim[2])

fields = np.linspace(fieldLim[0], fieldLim[1], fieldBuffer)

source = keithleypair.IVmax1024("GPIB::22", timeout = 60.0) #keithley object

mag = instruments.oxford_magnet("GPIB::20", rate = 0.2, timeout = 60.0)

daqGate = nidaqmx.AnalogOutputTask() #DAQ output object

daqGate.create_voltage_channel('Dev1/ao0', min_val = -10.0, max_val = 10.0)

daqGate.write([gate/gateAmp])

time.sleep(1.0)

#setup sweep and nanovoltmeter parameters

source.general_setup(beep = True)

currLim = [x/cvResistor for x in biasLim]

source.source_sweep_setup(currLim[0], currLim[1], currLim[2], srcDelay)

source.source_arm_setup()

source.source_trig_setup()

source.voltmeter_channel_setup(nplc, nvmRange, digital_filter = False)

source.voltmeter_trig_setup()

source.voltmeter_buffer_setup(biasBuffer)

realBuffer = int(source.ask(':sour:swe:poin?'))

if int(biasBuffer) != realBuffer:

raise RuntimeError('buffer sizes do not match: {0}, {1}'.format(int(biasBuffer), realBuffer))

#check that everything is setup

print 'source state = {}'.format(source.source_chk_op_evnt_reg())

print 'voltmeter state = {}'.format(source.voltmeter_chk_meas_evnt_reg())

#arm sweep

source.write_serial(':init:imm')

time.sleep(0.25)

source.write(":sour:swe:arm")

time.sleep(3.0)

mag.go_to_field(fieldLim[0], fieldDelay)

for field in fields:

print 'running IV for field = {}T'.format(field)

mag.go_to_field(field, fieldDelay)

data = np.array(source.execute_sweep(ivAvg = ivAvg, timeout = 120.0), dtype = np.floating)

data = data*cvAmp #calculate current from voltage measurement

for i in range(ivAvg): #save all data before averaging

np.savetxt(file, [np.insert(data[i], 0, field)], fmt = '%+.6e', delimiter = '\t')

self.file.flush(); os.fsync(self.file)

print data[i][0], data[i][1], '...', data[i][-2], data[i][-1]

data = data.mean(axis = 0) #average over multiple IV curves for plot

if msvcrt.kbhit():

if ord(msvcrt.getch()) == 113:

print "Program ended by user.\n"

break

print 'Cleaning up...'

source.write(":outp 0") #turn off current source

source.close()

mag.end_at_zero() #set field back to zero

mag.close()

daqGate.write([0.0]) #turn off gate

del mag, source, daqGate

self.file.close()

def run(self, *args, **kwargs):

""" This will run the animation as the main thread and start a

second thread for the measurement.

Takes all of the arguments and keyword arguments and passes them

to self.run_simple """

runArgs = args

runKwargs = kwargs

fileName = self.filename+'.dat'

def update_iv_field(num, fileName, title_text, line, ax):

data = np.loadtxt(fileName, dtype = np.floating)

line.set_ydata(data[-1,1:])

ax.set_ylim(np.amin(data[-1,1:]), np.amax(data[-1,1:]))

title_text.set_text('field = {}T'.format(data[-1,0]))

return line, title_text, ax

t = Thread(target = self.run_simple, args = runArgs, kwargs = runKwargs)

t.start()

time.sleep(5.0)

r = 0

while r <2:

data = np.loadtxt(fileName)

r = np.shape(data)[0] #wait for at least two rows to plot

fig = plt.figure()

ax = fig.add_subplot(111)

ax.set_xlim(data[0,1], data[0,-1])

ax.set_ylim(data[1,1]*1.25, data[1,-1]*1.25)

title_text = plt.title('gate = {}'.format(data[1, 0]))

line, = ax.plot(data[0,1:], data[1,1:],'r-')

plt.xlabel('bias')

plt.ylabel('measured')

line_ani = animation.FuncAnimation(fig, update_iv_gate, fargs=(fileName, title_text, line, ax),

interval=1000, blit=False)

""" Use the Keithley 6220 and 2182A to sweep IV curves for different

gate voltages. The function will save a plot each IV curve as it runs.

gateLim and biasLim should be arrays with 3 elements

[start, stop, step] given in volts.

Be sure to optimize the nanovoltmeter range. Setting it to 'auto'

is quite slow.

If you are sourcing current and measuring voltage, set the cvAmp and

current to voltage resistor to 1.0

To add a magnetic field, set it up manually. The field variable only

exists for logging purposes

To run: measurement = keithleypair_IV_Var.IV_DAQgate()

measurement.run(biasLim, gateLim, ...)

End early with 'q'. Do NOT close the plot before ending

the sweep. """

def __init__(self, filename = 'iv-DAQgate_{0:.0f}'.format(time.time())):

""" opens a file for the experiment. this means you have to start a new instance

of the class each time you want a new file. strange. maybe ok? """

self.filename = filename

self.file = open(filename+'.dat','a')

def run_simple(self, biasLim, gateLim, field = 0.0, ivAvg = 1,

cvResistor = 10.0, cvAmp = -1e-6, gateAmp = 9.1788,

srcDelay = 0.01, gateDelay = 1.0, nplc = 1, nvmRange = 0.1):

""" Runs the actual experiment. Can be called directly if plotting is

not needed. """

tools.write_log('iv_DAQgate', locals(), self.filename+'.log') #save hacked log-file

biasBuffer = tools.get_buffer_size(biasLim[0], biasLim[1], biasLim[2])

bias = np.linspace(biasLim[0], biasLim[1], biasBuffer)

data = np.zeros(biasBuffer)

gateBuffer = tools.get_buffer_size(gateLim[0], gateLim[1], gateLim[2])

gates = np.linspace(gateLim[0], gateLim[1], gateBuffer)

source = keithleypair.IVmax1024("GPIB::22", timeout = 30.0) #keithley object

daqGate = nidaqmx.AnalogOutputTask() #DAQ output object

daqGate.create_voltage_channel('Dev1/ao0', min_val = -10.0, max_val = 10.0)

#setup sweep and nanovoltmeter parameters

source.general_setup(beep = True)

currLim = [x/cvResistor for x in biasLim]

source.source_sweep_setup(currLim[0], currLim[1], currLim[2], srcDelay)

source.source_arm_setup()

source.source_trig_setup()

source.voltmeter_channel_setup(nplc, nvmRange, digital_filter = False)

source.voltmeter_trig_setup()

source.voltmeter_buffer_setup(biasBuffer)

realBuffer = int(source.ask(':sour:swe:poin?'))

if int(biasBuffer) != realBuffer:

raise RuntimeError('buffer sizes do not match: {0}, {1}'.format(int(biasBuffer), realBuffer))

#check that everything is setup

print 'source state = {}'.format(source.source_chk_op_evnt_reg())

print 'voltmeter state = {}'.format(source.voltmeter_chk_meas_evnt_reg())

#arm sweep

source.write_serial(':init:imm')

time.sleep(0.25)

source.write(":sour:swe:arm")

time.sleep(3.0)

np.savetxt(self.file, [np.insert(bias, 0, 0.0)], fmt = '%+.6e', delimiter = '\t')

for gate in gates:

print 'running IV for gate = {}V'.format(gate)

daqGate.write([gate/gateAmp])

time.sleep(gateDelay)

data = np.array(source.execute_sweep(ivAvg = ivAvg, timeout = 120.0), dtype = np.floating)

data = data*cvAmp #calculate current from voltage measurement

for i in range(ivAvg): #save all data before averaging

np.savetxt(self.file, [np.insert(data[i], 0, gate)], fmt = '%+.6e', delimiter = '\t')

self.file.flush(); os.fsync(self.file)

print data[i][0], data[i][1], '...', data[i][-2], data[i][-1]

data = data.mean(axis = 0) #average over multiple IV curves for plot

if msvcrt.kbhit():

if ord(msvcrt.getch()) == 113: #press 'q' to exit anytime

print "Program ended by user.\n"

break

print('Cleaning up...')

source.write(":outp 0") #turn off current source

source.close()

daqGate.write([0.0]) #turn off gate

del daqGate, source #delete DAQ object so it can be reused

self.file.close()

def run(self, *args, **kwargs):

""" This will run the animation as the main thread and start a

second thread for the measurement.

Takes all of the arguments and keyword arguments and passes them

to self.run_simple """

runArgs = args

runKwargs = kwargs

fileName = self.filename+'.dat'

def update_iv_gate(num, fileName, title_text, line, ax):

data = np.loadtxt(fileName, dtype = np.floating)

line.set_ydata(data[-1,1:])

ax.set_ylim(np.amin(data[-1,1:]), np.amax(data[-1,1:]))

title_text.set_text('gate = {}V'.format(data[-1,0]))

return line, title_text

t = Thread(target = self.run_simple, args = runArgs, kwargs = runKwargs)

t.start()

time.sleep(5.0)

l = 0

while l <2:

data = np.loadtxt(fileName)

l = len(np.shape(data))

fig = plt.figure()

ax = fig.add_subplot(111)

ax.set_xlim(np.amin(data[0,1:]), np.amax(data[0,1:]))

ax.set_ylim(np.amin(data[-1,1:]), np.amax(data[-1,1:]))

title_text = plt.title('gate = {}'.format(data[1, 0]))

line, = ax.plot(data[0,1:], data[1,1:],'r-')

plt.xlabel('bias')

plt.ylabel('measured')

line_ani = animation.FuncAnimation(fig, update_iv_gate, fargs=(fileName, title_text, line, ax),

interval=1000, blit=False)