Wavelength drift

Wavelength drift during analysis can also occur after prolonged use and must be corrected. If a straight line exhibits a correlation coefficient of r = 0.999 then the line is deemed acceptable. The following formula is generally used to calculate the r value of the calibration line ... 

Experimental results show that wavelength drifting is very linear with strain at any temperature. Wavelength drifting with temperature deviates from linearity at extreme temperatures in fact, under cryogenic conditions the linearity is lost, as seen in Fig. 11.6. At liquid helium temperature (4.2 K) both coefficients are almost zero and the wavelength with the temperature variation is negligible in these conditions. 

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