7
A microprocessor controlled LED 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.
FUNCTIONAL DESCRIPTION
1) Liquid Crystal Display (LCD)
2) Cuvet Holder
3) Cuvet alignment indicator
4) ON/OFF key
5) ZERO key
6) READ/TIMER key
7) CAL CHECK key
14
• Replace the cuvet into the holder and ensure
that the notch on the cap is positioned securely
into the groove.
• Hold READ/TIMER for three seconds. The
display will show the countdown prior to
measurement.
Alternatively, wait for 3 minutes and 30 seconds
and just press READ/TIMER.
In both cases “SIP” will blink during
measurement.
• The instrument directly displays concentration
in mg/L of ammonia nitrogen (NH
3
-N) on the
Liquid Crystal Display.
• To convert the reading to mg/L of ammonia
(NH
3
), multiply by a factor of 1.216.
or
INTERFERENCES
• Organic compounds like: chloramines, various aliphatic and aromatic amines, glycine,
(positive error).
To eliminate these interferences distillation is required.
• Organic compounds like: aldehydes, alcohols (e.g. ethanol) or acetone (negative error).
To eliminate these interferences distillation is required.
• Sulfide (S
2-
): may cause turbidity.
• Hardness above 1 g/L as Calcium Carbonate (CaCO
3
).
