Hanna Instruments HI 83742 - Manual (Page 7)

7
A microprocessor controlled special tungsten lamp emits radiation which is first optically conditioned
and beamed to the sample contained in the cuvet. The optical path is fixed by the diameter of the
cuvet. 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 cuvet 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) cuvets are
optically identical to provide the same measurement conditions. Whenever possible use the same
cuvet for both. It is necessary that the surface of the cuvet 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 cuvet walls with hands.
Furthermore, in order to maintain the same conditions during the zeroing and the measuring
phases, it is necessary to close the cuvet to prevent any contamination.
degree Celsius
degree Fahrenheit
grams per liter. g/L is equivalent to ppt (part per thousand)
milliliter
Liquid Crystal Display °C:
°F:
g/L:
mL:
LCD:
ABBREVIATIONS
22
MEASUREMENT MEASUREMENT MEASUREMENT MEASUREMENT MEASUREMENT
• Press “RANGE” to select the parameter code “P4” for
total phenols, white wine (see page 13).
• After a few seconds the display will show “-0.0-”.
The meter is now zeroed and ready for measurement.
• Remove the cuvet from the instrument.
• Insert the sample (cuvet #2) into the holder and
close the lid. #2
(Sample)
• Press READ/TIMER and “----” will blink during
measurement.
• The instrument directly displays concentration in g/L
of GAE (gallic acid equivalent) on the Liquid Crystal
Display.
Note: If the phenols concentration is 0,750 g/L or
higher, please repeat the test following the instruction
for red wine (page 23).
• Fill an empty cuvet with deionized water and replace
the cap. This is the zero zero zero zero zero.
#1
(Zero)
• Insert the zero cuvet into the holder and close the lid.
• Press ZERO and “----” will blink on the display.