Waters ACQUITY UPLC Operator's, Overview And Maintenance Manual page 15

Optics assembly components (Continued)
Component
Filter flag
Flow cell
Shunt
(not pictured)
Spectrograph
mirror and mask
Slit
Grating
Order filter
Function
Influences the light entering the flow cell. These are
the flag settings:
• Shutter – Prevents light from entering the flow cell.
In the shutter position, dark counts are measured at
each pixel and subsequently subtracted from
observed signal counts to give true signal counts.
• Open – Allows light to pass into the flow cell. It is
the normal setting when performing runs.
• Erbium – Inserts an erbium filter into the light
beam that allows the wavelength calibration to be
checked or updated.
• UV blocking filter – Inserts a UV blocking filter into
the light beam that minimizes light with
wavelengths shorter than, approximately, 210 nm.
Houses the segment of the flow path (containing eluent
and sample) through which the polychromatic light
beam passes.
Diagnostic tool used in place of the light-guiding flow
cell to emulate light transmission without fluid flow.
The mirror focuses light transmitted through the flow
cell onto the slit at the entrance to the spectrographic
portion of the optics. The mirror mask defines the size
of the beam at the grating.
Determines wavelength resolution and intensity of
light striking the photodiodes. The width of the slit is
100 µm (for the PDA) or 50 µm (for the eλPDA).
Blazed, holographic diffraction grating that disperses
light into bands of wavelengths and focuses them onto
the plane of the photodiode array.
Reduces the contribution of second-order diffraction of
UV light (less than 340 nm for PDA, or 370 nm for
eλPDA) to the light intensity observed at visible
wavelengths (greater than 340 nm for PDA, or 370 nm
for eλPDA).
Detector optics 3