Hanna Instruments HI 95761C Instruction Manual

Contents

7A microprocessor controlled special tungsten lamp emits radiation which is first optically conditionedand beamed to the sample contained in the cuvet. The optical path is fixed by the diameter of thecuvet. Then the light is spectrally filtered to a narrow spectral bandwidth, to obtain a light beam ofintensity Io or I.The photoelectric cell collects the radiation I that is not absorbed by the sample and converts itinto an electric current, producing a potential in the mV range.The microprocessor uses this potential to convert the incoming value into the desired measuringunit and to display it on the LCD.The measurement process is carried out in two phases: first the meter is zeroed and then the actualmeasurement is performed.The cuvet has a very important role because it is an optical element and thus requires particularattention. It is important that both the measurement and the calibration (zeroing) cuvets areoptically identical to provide the same measurement conditions. Whenever possible use the samecuvet for both. It is necessary that the surface of the cuvet is clean and not scratched. This to avoidmeasurement interference due to unwanted reflection and absorption of light. It is recommendednot to touch the cuvet walls with hands.Furthermore, in order to maintain the same conditions during the zeroing and the measuringphases, it is necessary to close the cuvet to prevent any contamination.1) Liquid Crystal Display (LCD)2) Cuvet Holder3) Cuvet alignment indicator4) ON/OFF key5) ZERO key6) READ/TIMER key7) CAL CHECK keyFUNCTIONAL DESCRIPTION14• Hold READ/TIMER for three seconds. Thedisplay will show the countdown prior tomeasurement.Alternatively, wait for 2 minutes and 30 secondsand just press READ/TIMER.In both cases “SIP” will blink duringmeasurement.• The instrument directly displays concentrationin mg/L of total chlorine on the Liquid CrystalDisplay.orINTERFERENCES• Alkalinity:• Acidity:• Hardness:• Bromine (Br2 ):• Chlorine dioxide (ClO2):• Iodine (I 2):• Oxidized Manganeseand Chromium:• Ozone (O 3):above 1,000 mg/L CaCO3 if present as bicarbonate (HCO3- , samplepH < 8.3); above 250 mg/L CaCO3 if present as carbonate (CO 32- ,sample pH > 9.0).In both cases, it will not reliably develop the full amount of coloror it may rapidly fade (negative error). To resolve this, neutralizethe sample with diluted HCl.above 150 mg/L CaCO 3 . May not reliably develop the full amountof color or it may rapidly fade (negative error). To resolve this,neutralize the sample with diluted NaOH.in case of water with hardness greater than 500 mg/L CaCO 3 ,shake the sample for approximately 2 minutes after adding thepowder reagent.positive error.positive error.positive error.positive error.positive error.

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