Hanna Instruments HI 96711 - Manual (Page 5)

8 9
1) RANGE/GLP/ key
2) CAL CHECK key
3) ZERO/CFM key
4) READ/ /TIMER key
5) ON/OFF key
6) Liquid Crystal Display (LCD)
7) Cuvette alignment indicator
8) Cuvette holder
FUNCTIONAL DESCRIPTION
A microprocessor controlled special tungsten lamp emits radiation which is first optically
conditioned and beamed to the sample contained in the cuvette. The optical path is fixed by the
diameter of the cuvette. Then the light is spectrally filtered to a narrow spectral bandwidth, to
obtain a light beam of intensity
I
o
or I.
The photoelectric cell collects the radiation I that is not absorbed by the sample and converts
it into an electric current, producing a potential in the mV range.
The microprocessor uses this potential to convert the incoming value into the desired measuring
unit and to display it on the LCD.
The measurement process is carried out in two phases: first the meter is zeroed and then the
actual measurement is performed.
The cuvette has a very important role because it is an optical element and thus requires
particular attention. It is important that both, the measurement and the calibration (zeroing)
cuvettes, are optically identical to provide the same measurement conditions. Whenever possible
use the same cuvette for both. It is necessary that the surface of the cuvette is clean and not
scratched. This to avoid measurement interference due to unwanted reflection and absorption of
light. It is recommended not to touch the cuvette walls with hands.
Furthermore, in order to maintain the same conditions during the zeroing and the measuring
phases, it is necessary to close the cuvette to prevent any contamination.
INSTRUMENT DESCRIPTION
KEYPAD DESCRIPTION
• ON/OFF: to turn the meter on and off.
• ZERO/CFM: this is a bi-functional key. Just press to zero the meter prior to measurement,
or confirm edited values. In calibration mode press to confirm factory calibration restore.
• READ/ /TIMER: this is a multi-functional key. In measurement mode, press to make a
measurement, or press and hold for three seconds to start a pre-programmed countdown prior
to measurement. In
GLP mode press to view the next screen.
• CAL CHECK: this is a bi-functional key. Just press to perform the validation of the meter, or
press and hold for three seconds to enter calibration mode.
• RANGE/GLP/ : this is a multi-functional key. Just press to change the parameter. Press
and hold for three seconds to enter GLP mode. In calibration mode press to edit the date and time.
OPERATING MODES
•
Measurement mode: default operation mode, enables both validation and measurement.
• Calibration mode: may be entered by keeping CAL CHECK pressed for three seconds ( the
“CAL” tag appears), it enables calibration of the instrument.
• GLP mode: may be entered by keeping RANGE/GLP/ pressed for three seconds (“GLP”
appears), it enables consulting of user calibration date or restore factory calibration.