
Overview
7
The grating images the slit onto the photodiode array. The angle of diffraction
from the grating determines the wavelength that strikes a particular
photodiode in the array.
The following figure shows an absorbance spectrum of benzene. Note that the
wavelength resolution is sufficient to resolve five principal absorption peaks.
Benzene spectrum at 1.2 nm resolution:
Measuring light at the photodiode array
The photodiode array detector measures the amount of light striking the
photodiode array to determine the absorbance of the sample in the flow cell.
The array consists of 512 photodiodes arranged in a row. Each photodiode acts
as a capacitor by holding a fixed amount of charge.
Light striking a photodiode discharges the diode. The magnitude of the
discharge depends on the amount of light striking the photodiode.
Ab
so
rbance
nm
Содержание ACQUITY UPC2
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