YSI 9300 Photometer - Manual (Page 7)

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2 OPERATING PRINCIPLE
The YSI photometers are instruments that measure color intensity. Light is
passed through a test tube containing the sample solution, and then through a
colored filter onto a photodetector. Filters have been chosen so that light of a
specific wavelength is selected. When the solution is completely colorless, all of
the light passes through the sample. With colored samples, light is absorbed
and the light which passes through the sample is proportionately reduced.
In the following test procedures, the photometer is used to measure the color
which is produced when chemical reagents are reacted with the water sample.
In these tests, the color intensity produced is proportional to the concentration
of the parameter being tested.
The photometer is pre-programmed with calibrations for each test parameter.
Different test procedures are carried out at different wavelengths to optimize
the sensitivity of each test. The required wavelength is selected automatically
by the instrument.
The calibrations are accessed by entering a unique program number at the start
of each test procedure. This enables the instrument to select the appropriate
wavelength filter automatically and allows the photodiode response to be
converted to a concentration reading. The instrument thus displays a direct-
reading of the test result.
The photometer is ideally suited for general analytical applications. The
instrument can be used as a laboratory or field photometer with user-generated
calibration graphs for standard analytical methods or for comparison of colored
solutions.
For general analytical applications, Transmittance (test program 0), or Absorbance
(test program 1) can be chosen.
Powering the Photometer
The Photometer is powered by (3) AAA batteries. The photometer features a
battery indicator – see ‘System Mode’ functions. A minimum voltage of 3.0V is
needed to operate the photometer. As a power-saving measure, in normal
use, both the 9300 and 9500 photometers automatically switch off five
minutes after the last key is pressed. The switch off period may be adjusted
for the 9500 in the System mode.
In addition to the above feature, a battery-warning message will appear
automatically on the display when the battery voltage becomes low. The batteries
should be replaced as soon as possible after the warning message appears.
Stored data in the instrument memory will not be lost during battery replacement.