Agilent Technologies 1100 Series Manual de Serviço descarregar pdf (Página 250)

250 1100 Series DAD and MWD Reference Manual

6 Introduction to the Detector

Temperature Correction

The quantum efficiency of the photodiode array depends on the temperature

and is different for each wavelength. The temperature dependency follows a

monotone increasing function over the wavelength scale, which means it

increases with longer wavelengths (above 600 nm).

To correct the intensity spectrum for temperature effects, the temperature on

the photodiode array is averaged. With the help of a function, correction

factors for each wavelength are calculated. The temperature factors are used

to correct the intensity spectrum.

Temperature Filter

The temperature filter determines whether the temperature has been changed

significantly. Only in this case, temperature correction is applied.

Absorbance Calculation and Filtering

To form an absorbance spectrum, the logarithm of the blank medium’s

intensity spectrum is subtracted from the logarithm of the sample’s intensity

spectrum.

Spectral filtering is used for noise reduction. Spectra are taken at faster rates

than the corresponding integration time, set in the Agilent ChemStation’s user

interface. Absorbance values of all wavelength form one absorbance spectrum.

Spectra Runbuffer (DAD Only)

Absorbance spectra are intermediately stored here if the acquisition of spectra

is faster than the processing and data communication to the

Agilent ChemStation. Intensity values can also be stored for special purposes,

for example, diagnostic reasons.

Wavelength Axis Linearization,

Deuterium Line Data,

Wavelength Calibration Table

1024 photodiodes are located on the array to give a sampling interval of

nominal <1 nm in the UV wavelength range. In the visible and short wave near

infrared wavelength ranges, the sampling interval is slightly higher. To correct

for this optical non-linearity and to convert from discrete diode distances to a

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Agilent Technologies 1100 Series Manual de Serviço Página 250