10
DESCRIPTION
Keypad Description
The keypad contains 12 direct keys and 3 functional keys with the following functions:
Press the functional keys to perform the function displayed above them on the LCD.
Press to access the list of photometer methods.
Press to move up in a menu or a help screen, to increment a set value, or to access
second level functions.
Press to toggle between photometer and pH (electrode) mode.
Press to move left in a menu or to decrement a set value.
Press to move down in a menu or a help screen, to decrement a set value, or to access
second level functions.
Press to move right in a menu or to increment a set value.
Press to access the setup screen.
Press to log the current reading.
Press to review saved logs.
Press to exit the current screen.
Press to display the help screen.
ON/OFF power button.
4.4. PRINCIPLE OF OPERATION
Absorption of light is a typical phenomenon of interaction between electromagnetic radiation and
matter. When a light beam crosses a substance, some of the radiation may be absorbed by atoms,
molecules or crystal lattices.
If pure absorption occurs, the fraction of light absorbed depends both on the optical path length
through the matter and on the physical‑chemical characteristics of the substance according to the
Lambert‑Beer Law:
‑log
I/I
o
=
e
l
c d
or
A =
e
l
c d
