1 # calibcant - tools for thermally calibrating AFM cantilevers
3 # Copyright (C) 2008-2012 W. Trevor King <wking@drexel.edu>
5 # This file is part of calibcant.
7 # calibcant is free software: you can redistribute it and/or modify it under
8 # the terms of the GNU General Public License as published by the Free Software
9 # Foundation, either version 3 of the License, or (at your option) any later
12 # calibcant is distributed in the hope that it will be useful, but WITHOUT ANY
13 # WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
14 # A PARTICULAR PURPOSE. See the GNU General Public License for more details.
16 # You should have received a copy of the GNU General Public License along with
17 # calibcant. If not, see <http://www.gnu.org/licenses/>.
19 """Calculate `k` from arrays of bumps, temperatures, and vibrations.
21 Separate the more general `analyze()` from the other calibration
22 functions in calibcant.
24 The relevent physical quantities are :
25 Vzp_out Output z-piezo voltage (what we generate)
26 Vzp Applied z-piezo voltage (after external ZPGAIN)
27 Zp The z-piezo position
28 Zcant The cantilever vertical deflection
29 Vphoto The photodiode vertical deflection voltage (what we measure)
30 Fcant The force on the cantilever
31 T The temperature of the cantilever and surrounding solution
32 (another thing we measure)
33 k_b Boltzmann's constant
35 Which are related by the parameters:
37 zp_sensitivity Zp / Vzp
38 photo_sensitivity Vphoto / Zcant
43 >>> from .config import CalibrateConfig
45 >>> config = CalibrateConfig()
46 >>> bumps = numpy.array((15.9e6, 16.9e6, 16.3e6))
47 >>> temperatures = numpy.array((295, 295.2, 294.8))
48 >>> vibrations = numpy.array((2.20e-5, 2.22e-5, 2.21e-5))
50 >>> k,k_s = analyze(bumps=bumps, temperatures=temperatures,
51 ... vibrations=vibrations)
52 >>> (k, k_s) # doctest: +ELLIPSIS
53 (0.0493..., 0.00248...)
55 Most of the error in this example comes from uncertainty in the
56 photodiode sensitivity (bumps).
58 >>> k_s/k # doctest: +ELLIPSIS
60 >>> bumps.std()/bumps.mean() # doctest: +ELLIPSIS
62 >>> temperatures.std()/temperatures.mean() # doctest: +ELLIPSIS
64 >>> vibrations.std()/vibrations.mean() # doctest: +ELLIPSIS
69 import numpy as _numpy
71 from scipy.constants import Boltzmann as _kB # in J/K
73 from scipy.constants import Bolzmann as _kB # in J/K
74 # Bolzmann -> Boltzmann patch submitted:
75 # http://projects.scipy.org/scipy/ticket/1417
76 # Fixed in scipy commit 4716d91, Apr 2, 2011, during work after v0.9.0rc5.
79 import matplotlib as _matplotlib
80 import matplotlib.pyplot as _matplotlib_pyplot
81 import time as _time # for timestamping lines on plots
82 except (ImportError, RuntimeError), e:
84 _matplotlib_import_error = e
86 from h5config.storage.hdf5 import h5_create_group as _h5_create_group
87 from pypiezo.base import get_axis_name as _get_axis_name
89 from . import LOG as _LOG
90 from . import package_config as _package_config
92 from .bump_analyze import analyze as _bump_analyze
93 from .bump_analyze import save as _bump_save
94 from .temperature_analyze import analyze as _temperature_analyze
95 from .temperature_analyze import save as _temperature_save
96 from .vibration_analyze import analyze as _vibration_analyze
97 from .vibration_analyze import save as _vibration_save
98 from .util import SaveSpec as _SaveSpec
99 from .util import save as _save
102 def analyze(bumps, temperatures, vibrations):
103 """Analyze data from `get_calibration_data()`
105 Inputs (all are arrays of recorded data):
106 bumps measured (V_photodiode / nm_tip) proportionality constant
107 temperatures measured temperature (K)
108 vibrations measured V_photodiode variance in free solution (V**2)
110 k cantilever spring constant (in N/m, or equivalently nN/nm)
111 k_s standard deviation in our estimate of k
115 We're assuming vib is mostly from thermal cantilever vibrations
116 (and then only from vibrations in the single vertical degree of
117 freedom), and not from other noise sources.
119 If the error is large, check the relative errors
120 (`x.std()/x.mean()`)of your input arrays. If one of them is
121 small, don't bother repeating that measurment too often. If one
122 is large, try repeating that measurement more. Remember that you
123 need enough samples to have a valid error estimate in the first
124 place, and that none of this addresses any systematic errors.
126 ps_m = bumps.mean() # ps for photo-sensitivity
128 T_m = temperatures.mean()
129 T_s = temperatures.std()
130 v2_m = vibrations.mean() # average voltage variance
131 v2_s = vibrations.std()
134 raise ValueError('invalid bumps: {}'.format(bumps))
136 raise ValueError('invalid temperatures: {}'.format(temperatures))
138 raise ValueError('invalid vibrations: {}'.format(vibrations))
140 # Vphoto / photo_sensitivity = x
141 # k = kB T / <x**2> = kB T photo_sensitivity**2 / Vphoto_var
143 # units, photo_sensitivity = Vphoto/(Zcant in m),
144 # so Vphoto/photo_sensitivity = Zcant in m
145 # so k = J/K * K / m^2 = J / m^2 = N/m
146 k = _kB * T_m * ps_m**2 / v2_m
148 # propogation of errors
152 dk_ps = 2*k/ps_m * ps_s
154 dk_v = -k/v2_m * v2_s
156 k_s = _numpy.sqrt(dk_T**2 + dk_ps**2 + dk_v**2)
158 _LOG.info('variable (units) : '
159 'mean +/- std. dev. (relative error)')
160 _LOG.info('cantilever k (N/m) : %g +/- %g (%g)' % (k, k_s, k_s/k))
161 _LOG.info('photo sensitivity (V/m) : %g +/- %g (%g)'
162 % (ps_m, ps_s, ps_s/ps_m))
163 _LOG.info('T (K) : %g +/- %g (%g)'
164 % (T_m, T_s, T_s/T_m))
165 _LOG.info('vibration variance (V^2) : %g +/- %g (%g)'
166 % (v2_m, v2_s, v2_s/v2_m))
168 if _package_config['matplotlib']:
169 plot(bumps, temperatures, vibrations)
174 def plot(bumps, temperatures, vibrations):
176 raise _matplotlib_import_error
177 figure = _matplotlib_pyplot.figure()
179 bump_axes = figure.add_subplot(3, 1, 1)
180 T_axes = figure.add_subplot(3, 1, 2)
181 vib_axes = figure.add_subplot(3, 1, 3)
183 timestamp = _time.strftime('%H%M%S')
184 bump_axes.set_title('cantilever calibration %s' % timestamp)
186 bump_axes.autoscale(tight=True)
187 bump_axes.plot(bumps, 'g.-')
188 bump_axes.set_ylabel('photodiode sensitivity (V/m)')
189 T_axes.autoscale(tight=True)
190 T_axes.plot(temperatures, 'r.-')
191 T_axes.set_ylabel('temperature (K)')
192 vib_axes.autoscale(tight=True)
193 vib_axes.plot(vibrations, 'b.-')
194 vib_axes.set_ylabel('thermal deflection variance (V^2)')
196 if hasattr(figure, 'show'):
199 _plot = plot # alternative name for use inside analyze_all()
201 def save_results(filename=None, group='/', bump=None,
202 temperature=None, vibration=None, spring_constant=None,
203 spring_constant_deviation=None):
205 _SaveSpec(item=bump, relpath='raw/photodiode-sensitivity',
206 array=True, units='V/m'),
207 _SaveSpec(item=temperature, relpath='raw/temperature',
208 array=True, units='K'),
209 _SaveSpec(item=vibration, relpath='raw/vibration',
210 array=True, units='V^2/Hz'),
211 _SaveSpec(item=spring_constant, relpath='processed/spring-constant',
212 units='N/m', deviation=spring_constant_deviation),
214 _save(filename=filename, group=group, specs=specs)
216 def analyze_all(config, data, raw_data, maximum_relative_error=1e-5,
217 filename=None, group=None, plot=False, dry_run=False):
218 "(Re)analyze (and possibly plot) all data from a `calib()` run."
219 if not data.get('bump', None):
220 data['bump'] = _numpy.zeros((config['num-bumps'],), dtype=float)
221 if not data.get('temperature', None):
222 data['temperature'] = _numpy.zeros(
223 (config['num-temperatures'],), dtype=float)
224 if not data.get('vibrations', None):
225 data['vibration'] = _numpy.zeros(
226 (config['num-vibrations'],), dtype=float)
227 axis_config = config['afm']['piezo'].select_config(
229 attribute_value=config['afm']['main-axis'],
230 get_attribute=_get_axis_name)
231 input_config = config['afm']['piezo'].select_config(
232 setting_name='inputs', attribute_value='deflection')
233 bumps_changed = temperatures_changed = vibrations_changed = False
234 calibration_group = None
235 if not isinstance(group, _h5py.Group) and not dry_run:
236 f = _h5py.File(filename, mode='a')
237 group = _h5_create_group(f, group)
241 if len(data.get('raw/bump', [])) != len(data['bump']):
243 for i,bump in enumerate(raw_data['bump']):
244 data['bump'][i],changed = check_bump(
245 index=i, bump=bump, z_axis_config=axis_config,
246 deflection_channel_config=input_config, plot=plot,
247 maximum_relative_error=maximum_relative_error)
248 if changed and not dry_run:
250 bump_group = _h5_create_group(group, 'bump/{}'.format(i))
251 _bump_save(group=bump_group, processed=data['bump'][i])
252 if len(data.get('raw/temperature', [])) != len(data['temperature']):
253 temperatures_changed = True
254 for i,temperature in enumerate(raw_data['temperature']):
255 data['temperature'][i],changed = check_temperature(
256 index=i, temperature=temperature,
257 maximum_relative_error=maximum_relative_error)
258 if changed and not dry_run:
259 temperatures_changed = True
260 temperature_group = _h5_create_group(
261 group, 'temperature/{}'.format(i))
263 group=temerature_group, processed=data['temperature'][i])
264 if len(data.get('raw/vibration', [])) != len(data['vibration']):
265 vibrations_changed = True
266 for i,vibration in enumerate(raw_data['vibration']):
267 data['vibration'][i],changed = check_vibration(
268 index=i, vibration=vibration,
269 deflection_channel_config=input_config, plot=plot,
270 maximum_relative_error=maximum_relative_error)
271 if changed and not dry_run:
272 vibrations_changed = True
273 vibration_group = _h5_create_group(
274 group, 'vibration/{}'.format(i))
276 group=vibration_group, processed=data['vibration'])
277 if (bumps_changed or temperatures_changed or vibrations_changed
279 calibration_group = _h5_create_group(group, 'calibration')
282 group=calibration_group, bump=data['bump'])
283 if temperatures_changed:
285 group=calibration_group, temperature=data['temperature'])
286 if vibrations_changed:
288 group=calibration_group, vibration=data['vibration'])
289 if len(raw_data['bump']) != len(data['bump']):
291 'not enough raw bump data: {} of {}'.format(
292 len(raw_data['bump']), len(data['bump'])))
293 if len(raw_data['temperature']) != len(data['temperature']):
295 'not enough raw temperature data: {} of {}'.format(
296 len(raw_data['temperature']), len(data['temperature'])))
297 if len(raw_data['vibration']) != len(data['vibration']):
299 'not enough raw vibration data: {} of {}'.format(
300 len(raw_data['vibration']), len(data['vibration'])))
301 k,k_s,changed = check_calibration(
302 k=data.get('processed/spring_constant', None),
303 k_s=data.get('processed/spring_constant_deviation', None),
305 temperatures=data['temperature'], vibrations=data['vibration'],
306 maximum_relative_error=maximum_relative_error)
307 if changed and not dry_run:
308 if calibration_group is None:
309 calibration_group = _h5_create_group(group, 'calibration')
311 group=calibration_group,
312 spring_constant=k, spring_constant_deviation=k_s)
317 _plot(bumps=data['raw']['bump'],
318 temperatures=data['raw']['temperature'],
319 vibrations=data['raw']['vibration'])
322 def check_bump(index, bump, maximum_relative_error, **kwargs):
324 sensitivity = _bump_analyze(
325 config=bump['config']['bump'], data=bump['raw'], **kwargs)
326 if bump.get('processed', None) is None:
328 _LOG.warn('new analysis for bump {}: {}'.format(index, sensitivity))
330 rel_error = abs(sensitivity - bump['processed'])/bump['processed']
331 if rel_error > maximum_relative_error:
333 _LOG.warn(("new analysis doesn't match for bump {}: {} -> {} "
334 "(difference: {}, relative error: {})").format(
335 index, bump['processed'], sensitivity,
336 sensitivity-bump['processed'], rel_error))
337 return (sensitivity, changed)
339 def check_temperature(index, temperature, maximum_relative_error, **kwargs):
341 temp = _temperature_analyze(
342 config=temperature['config']['temperature'],
343 temperature=temperature['raw'], **kwargs)
344 if temperature.get('processed', None) is None:
346 _LOG.warn('new analysis for temperature {}: {}'.format(index, temp))
348 rel_error = abs(temp - temperature['processed']
349 )/temperature['processed']
350 if rel_error > maximum_relative_error:
352 _LOG.warn(("new analysis doesn't match for temperature "
353 "{} -> {} (difference: {}, relative error: {})"
355 index, temperature['processed'], temp,
356 temp-temperature['processed'], rel_error))
357 return (temp, changed)
359 def check_vibration(index, vibration, maximum_relative_error, **kwargs):
361 variance = _vibration_analyze(
362 config=vibration['config']['vibration'],
363 deflection=vibration['raw'], **kwargs)
364 if vibration.get('processed', None) is None:
366 _LOG.warn('new analysis for temperature {}: {}'.format(
369 rel_error = abs(variance-vibration['processed'])/vibration['processed']
370 if rel_error > maximum_relative_error:
371 _LOG.warn(("new analysis doesn't match for vibration {}: {} != {} "
372 "(difference: {}, relative error: {})").format(
373 index, variance, vibration['processed'],
374 variance-vibration['processed'], rel_error))
375 return (variance, changed)
377 def check_calibration(k, k_s, maximum_relative_error, **kwargs):
379 new_k,new_k_s = analyze(**kwargs)
382 _LOG.warn('new analysis for the spring constant: {}'.format(new_k))
384 rel_error = abs(new_k-k)/k
385 if rel_error > maximum_relative_error:
387 _LOG.warn(("new analysis doesn't match for the spring constant: "
388 "{} != {} (difference: {}, relative error: {})").format(
389 new_k, k, new_k-k, rel_error))
392 _LOG.warn('new analysis for the spring constant deviation: {}'.format(
395 rel_error = abs(new_k_s-k_s)/k_s
396 if rel_error > maximum_relative_error:
399 ("new analysis doesn't match for the spring constant deviation"
400 ": {} != {} (difference: {}, relative error: {})").format(
401 new_k_s, k_s, new_k_s-k_s, rel_error))
402 return (new_k, new_k_s, changed)