1 I just reran Marissa's calibration. My original output (from the old
2 gnuplot-fitted ~/.python/calibrate_cantilever.py) had produced
4 $ cat 20081215/20081215101516_analysis_text
5 k (N/m) : 0.0471212 +/- 0.0132663
6 a**2 (V/nm)**2 : 0.000191658 +/- 1.36722e-06
7 T (K) : 295.15 +/- 5.68434e-14
8 1/Vp**2 (1/V)**2 : 60334.2 +/- 16980.8
9 $ cat 20081215/20081215124856_analysis_text
10 k (N/m) : 0.0346675 +/- 0.0118672
11 a**2 (V/nm)**2 : 0.000217743 +/- 1.08297e-06
12 T (K) : 295.15 +/- 5.68434e-14
13 1/Vp**2 (1/V)**2 : 39070.7 +/- 13373.1
15 Using all the defaults (and only the second take for the first
16 calibration). However, once I'd set up the tweakfiles and ran
17 20081215_calibrate.sh, I got
19 $ cat 20081215/20081215101516_analysis_text
20 Variable (units) : mean +/- std. dev. (relative error)
21 Cantilever k (N/m) : 0.0656644 +/- 0.00107743 (0.016408)
22 photoSensitivity**2 (V/nm)**2 : 0.000190122 +/- 1.86869e-06 (0.00982893)
23 T (K) : 295.15 +/- 5.68434e-14 (1.92592e-16)
24 1/Vphoto**2 (1/V)**2 : 84756.3 +/- 1113.56 (0.0131383)
25 $ cat 20081215/20081215124856_analysis_text
26 Variable (units) : mean +/- std. dev. (relative error)
27 Cantilever k (N/m) : 0.0494809 +/- 0.000855265 (0.0172848)
28 photoSensitivity**2 (V/nm)**2 : 0.000217743 +/- 1.08297e-06 (0.00497362)
29 T (K) : 295.15 +/- 5.68434e-14 (1.92592e-16)
30 1/Vphoto**2 (1/V)**2 : 55765.6 +/- 923.129 (0.0165537)
32 Comparing the two, we see:
34 k 0.0471212 -> 0.0656644 (with a 92% drop in error)
35 photoSensitivity 0.000191658 (little change)
37 1/Vphoto**2 60334.2 -> 84756.3 (with a 94% drop in error)
39 k 0.0346675 -> 0.0494809 (with a 93% drop in error)
40 photoSensitivity 0.000217743 (no change)
42 1/Vphoto**2 39070.7 -> 55765.6 (with a 93% drop in error)
44 I don't have hard evidence yet, but I am confident this discrepancy is
45 due to poor fitting with the older calibration file.