Agilent Technologies 1100 Series Reference Manual page 250

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
250 1100 Series DAD and MWD Reference Manual