Hanna Instruments hi 95721 User Manual
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
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
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.
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.
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
2) Cuvet Holder
3) Cuvet alignment indicator
4) ON/OFF key
5) ZERO key
6) READ/TIMER key
7) CAL CHECK key
FUNCTIONAL DESCRIPTION
14
• Hold READ/TIMER for three seconds. The
display will show the countdown prior to
measurement.
Alternatively, wait for 3 minutes and just
press READ/TIMER.
In both cases “SIP” will blink during
measurement.
Alternatively, wait for 3 minutes and just
press READ/TIMER.
In both cases “SIP” will blink during
measurement.
• The instrument directly displays
concentration in mg/L of iron on the Liquid
Crystal Display.
Crystal Display.
or
INTERFERENCES
• Alkalinity:
• Calcium (Ca
2+
):
• Copper (Cu
2+
):
• Magnesium (Mg
2+
):
• Molybdate:
• High Iron concentrations:
• High sulfide (S
2-
)
concentrations:
• pH:
• Silica (SiO
2
):
above 2,000 mg/L (as CaCO
3
). May slow down color development
(negative error).
To resolve this, neutralize the sample with diluted HCl.
above 10,000 mg/L (as CaCO
To resolve this, neutralize the sample with diluted HCl.
above 10,000 mg/L (as CaCO
3
).
does not interfere: reagent contains a masking agent.
above 100,000 mg/L (as CaCO
above 100,000 mg/L (as CaCO
3
).
above 25 mg/L (as Mo-MoO
2-
4
) (positive error).
Samples containing up to 50 mg/L Mo-MoO
2-
4
may be measured if a
reading is taken after 1 minute instead of 3 minutes.
up to 200 mg/L do not inhibit color development;
up to 200 mg/L do not inhibit color development;
above 200 mg/L color development may be inhibited.
high sulfide concentrations may interfere.
To reduce sulfide: acidify the sample and boil for about 20 minutes,
neutralize and adjust volume before measurements.
a sample pH < 3 may develop an altered color. Adjust the sample
pH to 3-5 before taking measurements by adding iron-free acid and
making a volume correction if necessary.
above 175 mg/L (as SiO
high sulfide concentrations may interfere.
To reduce sulfide: acidify the sample and boil for about 20 minutes,
neutralize and adjust volume before measurements.
a sample pH < 3 may develop an altered color. Adjust the sample
pH to 3-5 before taking measurements by adding iron-free acid and
making a volume correction if necessary.
above 175 mg/L (as SiO
2
). May slow down color development (negative
error).