Figure 1
1.
Photometer Design
Photometer "ET2020" is a small---sized portable device (Fig. 1), which is powered by a 6V AC
adapter or by 4 AA batteries.
The device consists of a cuvette compartment suitable for a
standard 10 mm cuvette (1), display (2), and keypad (3).
Inside, there is an optical unit, and a control and data
processing unit.
The optical unit includes 2 or 8 highly stable semiconductor
LEDs, which are used as light sources. The photodiode
incorporated in the optical units serves as light radiation
receiver. The control unit providing self---diagnostic control
functions, data processing and wavelength selection is based
on a microprocessor.
The unit can be connected to PC via the built---in RS---232 interface (4).
The interface is placed on the upper end wall (Fig. 2). Next to the
interface is a socket for a connection to an external power supply
(5).
The alternative power supply source of 4 AA batteries can be inserted in the compartment
located on the bottom wall. A removable cover closes the compartment with the batteries. The
device readings are on the LCD display with a bright backlight (Fig. 1---2). The display is located
on the upper part of the front panel.
The keypad with six buttons (Fig. 3) is on the same panel and
located between the LCD and the cuvette compartment. The
keypad controls are responsible for the use of the following
functions:
ENTER --- confirmation of action and display backlight on/off
CANCEL – cancellation of action
«←» selection of the wavelength in decreasing mode;
«→» selection of the wavelength in increasing mode;
ON--- turn on;
OFF--- turn off;
Both above mentioned keys could be used also for selection of the
mode “Autoselect” which helps to find a wavelength providing a
maximum absorbance value for the solution to be analyzed. *
Figure 2
Figure 3