Hanna Instruments HI 83741 - 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.
US Environmental Protection Agency
degree Celsius
degree Fahrenheit
milligrams per liter. mg/L is equivalent to ppm (part per million)
milliliter
Liquid Crystal Display EPA:
°C:
°F:
mg/L:
mL:
LCD:
ABBREVIATIONS
14
#2
• Place the cuvet into the holder and close
the lid.
• Press TIMER and the instrument will show the
countdown or, alternatively, wait for 2 minutes.
The instrument gives an acoustic signal to
alert the user that the countdown is finished.
• Press ZERO and “----” will blink on the display.
• Remove the cuvet from the instrument and
open the cap.
• Add the content of one powder packet of
HI 83741B-0 reagent B. Replace the cap and
shake gently for 1 minute to dissolve the
reagent.
• After a few seconds the display will show
“-0.0-”. The meter is now zeroed and ready
for measurement
Note: If the “L Lo” (Low Light) message
appears, the sample must be diluted. See
“General tips for an accurate measurement”
(page 11).