201 lines
6.6 KiB
Python
201 lines
6.6 KiB
Python
# -*- coding: iso-8859-1 -*-
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from numpy import *
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from scipy.signal import *
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from scipy.optimize import *
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from os import path, rename
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def result():
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measurement = MeasurementResult('Magnetization')
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measurement_range = [0.0, 10e-6]
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measurement_ranging = True
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suffix = '' # output file name's suffix and...
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counter = 1 # counter for arrayed experiments
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var_key = '' # variable parameter name
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# loop over the incoming results:
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for timesignal in results:
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if not isinstance(timesignal,ADC_Result):
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continue
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# read experiment parameters:
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pars = timesignal.get_description_dictionary()
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# ---------------- digital filter ------------------
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# get actual sampling rate of timesignal:
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sampling_rate = timesignal.get_sampling_rate()
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# get user-defined spectrum width:
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spec_width = pars['SW']
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# specify cutoff frequency, in relative units:
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cutoff = spec_width / sampling_rate
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if cutoff < 1: # otherwise no filter applied
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# number of filter's coefficients:
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numtaps = 29
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# use firwin to create a lowpass FIR filter:
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fir_coeff = firwin(numtaps, cutoff)
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# downsize x according to user-defined spectral window:
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skip = int(sampling_rate / spec_width)
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timesignal.x = timesignal.x[::skip]
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for i in range(2):
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# apply the filter to ith channel:
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timesignal.y[i] = lfilter(fir_coeff, 1.0, timesignal.y[i])
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# zeroize first N-1 "corrupted" samples:
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timesignal.y[i][:numtaps-1] = 0.0
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# circular left shift of y:
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timesignal.y[i] = roll(timesignal.y[i], -(numtaps-1))
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# downsize y to user-defined number of samples (SI):
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timesignal.y[i] = timesignal.y[i][::skip]
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# update the sampling_rate attribute of the signal's:
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timesignal.set_sampling_rate(spec_width)
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# ----------------------------------------------------
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# rotate timesignal according to current receiver's phase:
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timesignal.phase(pars['rec_phase'])
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# provide timesignal to the display tab:
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data['Current scan'] = timesignal
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# accumulate...
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if not locals().get('accu'):
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accu = Accumulation()
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# skip dummy scans, if any:
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if pars['run'] < 0: continue
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# add up:
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accu += timesignal
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# provide accumulation to the display tab:
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data['Accumulation'] = accu
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# check how many scans are done:
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if accu.n == pars['NS']: # accumulation is complete
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# make a copy:
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echo = accu + 0
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# compute the signal's phase:
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phi0 = arctan2(echo.y[1][0], echo.y[0][0]) * 180 / pi
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if not locals().get('ref'): ref = phi0
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print 'phi0 = ', phi0
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# rotate the signal to maximize Re (optional):
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#echo.phase(-phi0)
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# specify noise level:
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if not locals().get('noise'):
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noise = 0.1*max(abs(echo.y[0]))
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samples = echo.y[0] > noise
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# check whether it is an arrayed experiment:
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var_key = pars.get('VAR_PAR')
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if var_key:
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# get variable parameter's value:
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var_value = pars.get(var_key)
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# provide signal recorded with this var_value to the display tab:
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data['Accumulation'+"/"+var_key+"=%e"%(var_value)] = accu
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# measure signal intensity vs. var_value:
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if measurement_ranging == True:
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[start, stop] = echo.get_sampling_rate() * array(measurement_range)
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measurement[var_value] = sum(echo.y[0][int(start):int(stop)])
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else:
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measurement[var_value] = sum(echo.y[0][samples])
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# provide the measurement result to the display tab:
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data[measurement.get_title()] = measurement
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# update the file name suffix:
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suffix = '_' + str(counter)
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counter += 1
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# save accu if required:
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outfile = pars.get('OUTFILE')
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if outfile:
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datadir = pars.get('DATADIR')
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# write raw data in Simpson format:
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filename = datadir+outfile+suffix+'.dat'
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if path.exists(filename):
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rename(filename, datadir+'~'+outfile+suffix+'.dat')
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accu.write_to_simpson(filename)
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# write raw data in Tecmag format:
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# filename = datadir+outfile+'.tnt'
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# accu.write_to_tecmag(filename, nrecords=20)
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# write parameters in a text file:
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filename = datadir+outfile+suffix+'.par'
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if path.exists(filename):
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rename(filename, datadir+'~'+outfile+suffix+'.par')
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fileobject = open(filename, 'w')
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for key in sorted(pars.iterkeys()):
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if key=='run': continue
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if key=='rec_phase': continue
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fileobject.write('%s%s%s'%(key,'=', pars[key]))
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fileobject.write('\n')
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fileobject.close()
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# reset accumulation:
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del accu
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if var_key == 'D2':
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# mono-exponential decay fit:
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xdata = measurement.get_xdata()
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ydata = measurement.get_ydata()
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[amplitude, rate] = fitfunc(xdata, ydata)
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print '%s%02g' % ('Amplitude = ', amplitude)
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print '%s%02g' % ('T1 [s] = ', 1./rate)
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# update display for the fit:
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measurement.y = func([amplitude, rate], xdata)
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data[measurement.get_title()] = measurement
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# the fitting procedure:
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def fitfunc(xdata, ydata):
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# initialize variable parameters:
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try:
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# solve Az = b:
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A = array((ones(xdata.size/2), xdata[0:xdata.size/2]))
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b = log(abs(ydata[0:xdata.size/2]))
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z = linalg.lstsq(transpose(A), b)
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amplitude = exp(z[0][0])
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rate = -z[0][1]
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except:
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amplitude = abs(ydata[0])
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rate = 1./(xdata[-1] - xdata[0])
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p0 = [amplitude, rate]
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# run least-squares optimization:
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plsq = leastsq(residuals, p0, args=(xdata, ydata))
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return plsq[0] # best-fit parameters
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def residuals(p, xdata, ydata):
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return ydata - func(p, xdata)
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# here is the function to fit:
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def func(p, xdata):
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return p[0]*exp(-p[1]*xdata)
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pass |