Hanna Instruments HI 96741C Instruction Manual

6 7PRINCIPLE OF OPERATIONAbsorption of Light is a typical phenomenon of interaction between electromagnetic radiation andmatter. When a light beam crosses a substance, some of the radiation may be absorbed byatoms, molecules or crystal lattices.If pure absorption occurs, the fraction of light absorbed depends both on the optical path lengththrough the matter and on the physical-chemical characteristics of the substance according to theLambert-Beer Law:-log I/Io = ελ c dorA = ελ c dWhere:-log I/Io = Absorbance (A)Io = intensity of incident light beamI = intensity of light beam after absorptionελ = molar extinction coefficient at wavelength λc = molar concentration of the substanced = optical path through the substanceTherefore, the concentration "c" can be calculated from the absorbance of the substance as theother factors are known.Photometric chemical analysis is based on the possibility to develop an absorbing compoundfrom a specific chemical reaction between sample and reagents. Given that the absorption of acompound strictly depends on the wavelength of the incident light beam, a narrow spectralbandwidth should be selected as well as a proper central wavelength to optimize measurements.The optical system of Hanna's HI 96 series colorimeters is based on special subminiaturetungsten lamps and narrow-band interference filters to guarantee both high performance andreliable results.HI 96 series block diagram (optical layout)SPECIFICATIONSPRECISION AND ACCURACYRange Mg Hardness 0.00 to 2.00 mg/LCa Hardness 0.00 to 2.70 mg/LTotal Hardness 0.00 to 4.70 mg/LIron LR 0.00 to 1.60 mg/LResolution 0.01 mg/L Total Hardness0.01 mg/L Iron LRAccuracy Mg Hardness ±0.11 mg/L ±5% of reading @ 25°CCa Hardness ±0.11 mg/L ±5% of reading @ 25°CIron LR ±0.01 mg/L ±8% of reading @ 25°CTypical EMC Deviation ±0.02 mg/L Mg Hardness±0.02 mg/L Ca Hardness±0.01 mg/L Iron LRLight Source Tungsten lampLight Detector Silicon Photocell with narrow band interference filter @ 525nm.Method For Total Hardness: Adaptation of theStandard Methods for the Examinationof Water and Wastewater, 18th Edition, colorimetric method. The reactionbetween Mg/Ca and reagents causes a violet tint in the sample.For Iron LR: Adaptation of the TPTZ method. The reaction between iron andthe reagent causes a violet tint in the sample.Environment 0 to 50°C (32 to 122°F); max 95% RH non-condensingBattery Type 1 x 9 voltAuto-Shut off After 10' of non-use inmeasurement mode;after 1 hour of non-use incalibration mode;with last reading reminder.Dimensions 192 x 104 x 69 mm (7.6 x 4.1 x 2.7")Weight 360 g (12.7 oz.).REQUIRED REAGENTSCode Unit Description Quantity/testHI 93719A-0 Hardness Ca and Mg Reagent 0.5 mLHI 93719B-0 Hardness Alkaly Solution 0.5 mLHI 93719C-0 Hardness EDTA Solution 1 dropHI 93719D-0 Hardness EGTA Solution 1 dropHI 93741-0 Iron LR TPTZ Reagent 1 packetPrecision is how closely repeated measurementsagree with each other. Precision is usually expressedas standard deviation (SD).Accuracy is defined as the nearness of a test resultto the true value.Although good precision suggests good accuracy,precise results can be inaccurate. The figure explainsthese definitions. In a laboratory using a standardsolution of 1.00 mg/L chlorine and a representativelot of reagent, an operator obtained with a singleinstrument a standard deviation of 0.02 mg/L.