Ocean Optics NIR - Manual (Page 23)

A: Calibrating the Wavelength of the NIR Spectrometer
Independent Dependent Values computed from
Variable Variables the regression output
True Wavelength (nm) Pixel # Pixel # 2 Pixel # 3
Predicted
Wavelength
Difference
253.65
296.73
302.15
313.16
334.15
365.02
404.66
407.78
435.84
546.07
576.96
579.07
696.54
706.72
727.29
738.40
751.47 175
296
312
342
402
490
604
613
694
1022
1116
1122
1491
1523
1590
1627
1669
30625
87616
97344
116964
161604
240100
364816
375769
481636
1044484
1245456
1258884
2223081
2319529
2528100
2647129
2785561
5359375
25934336
30371328
40001688
64964808
117649000
220348864
230346397
334255384
1067462648
1389928896
1412467848
3314613771
3532642667
4019679000
4306878883
4649101309
253.56
296.72
302.40
313.02
334.19
365.05
404.67
407.78
435.65
546.13
577.05
579.01
696.70
706.62
727.24
738.53
751.27 0.09
0.01
-0.25
0.13
-0.05
-0.04
-0.01
0.00
0.19
-0.06
-0.09
0.06
-0.15
0.10
0.06
-0.13
0.19
5. Use your spreadsheet or calculator to calculate the wavelength calibration coefficients. In your
spreadsheet program, find the functions to perform linear regressions.
• If using Quattro Pro, look under Tools | Advanced Math
• If using Excel, look under Analysis ToolPak
6. Select the true wavelength as the dependent variable (Y). Select the pixel number, pixel number
squared, and the pixel number cubed as the independent variables (X). After you execute the
regression, an output similar to the one shown below is obtained.
Regression Statistics
Multiple R 0.999999831
R Square 0.999999663 R Squared
Adjusted R Square 0.999999607
Standard Error 0.125540214
Observations 22
intercept
Coefficients Standard Error
Intercept 190.473993 0.369047536 first coefficient
X Variable 1 0.36263983 0.001684745
X Variable 2 -1.174416E-05 8.35279E-07
X Variable 3 -2.523787E-09 2.656608E-10 second coefficient
third coefficient
The numbers of importance are indicated in the above figure.
197-00000-512-02-0707 17