Appendix E: System Overview & Principles - Siemens CLINITEK Status Operator's Manual

10 Appendices
Appendix E: System Overview & Principles
Appendix E: System Overview & Principles
Description of Optical System
The optical system consists of six
light emitting diodes, a light guide,
a mirror, a lens and a detector.
Light from the LEDs travels along
the light guide and is reflected off
the calibration bar, strip or cassette
onto the mirror. It is then directed
through an aperture on the lens,
from where it is focused onto the
detector. The light intensity
detected is converted into electrical
impulses, which are processed by
the instrument's microprocessor
and converted into clinically
meaningful results.
When carrying out analysis on a
urinalysis strip, the test table
positions strip pads in the "read
area". The light reflected at specific
wavelengths (470 nm, 525 nm,
565 nm, 625 nm, 660 nm and
845 nm) from the test pad is
dependent upon the degree of color
change in the pad and is directly
related to the concentration of the
particular constituent in the urine.
The analyzer's optical system
images the entire strip (i.e., all
reagent pads at once).
10-12
When using a Clinitest immunoassay
cassette, the detector will scan the
"read area" for the test, reference
and control lines that form after
urine has been applied. The
reference and control lines will
always form whereas the test line
will only form if hCG is present in
the sample.
Description of Internal Checks
When the analyzer is first turned
on, the instrument performs a
series of electronic, signal and
memory checks, as well as
ensuring there is sufficient battery
voltage to operate the instrument (if
powered by batteries).
Each time a urinalysis strip is read,
the instrument positions the table
correctly and checks the electronics
and signals. It then takes reference
readings off the white calibration
bar on the test table. The readings
are taken at all six wavelengths and
are then used to calculate the
sample readings.