Development of the U-50 Series Multi-parameter Water Quality ...

Development of the U-50 Series Multi-parameter Water Quality CheckerYuichiro Komatsu, Katsunobu Ehara, Katsuaki OguraWater and Temperature Measurement R&D Dept. HORIBA Ltd., Kyoto, JapanAbstract: Multi-parameter water qualitychecker named U-50 capable of simultaneouslymeasuring turbidity, dissolved oxygen,conductivity, pH, oxidation-reduction potential(ORP), water depth, and temperature wasdeveloped. This series equipped with thehigh-sensitivity turbidity meter compliant withEPA Method 180.1, and the easy-to-maintaindissolved oxygen electrode. The dissolved oxygenelectrode and conductivity features an expandedmeasurement range for high concentrations.Compared to the earlier model U-20, usabilityimprovements were made to the GPS function,simultaneous display of all parameters, and datastorage function. The U-50 series is expected toprovide a new measurement application whichwas not able to be handled by the U-20.Keywords: Water quality checker, U-50, EPAchecker U-50. The display unit and sensor probeeach weigh approximately 0.8 kg and 1.8 kg,respectively. These components are connected viaa cable with a maximum length of 30 m. Thesensor probe is deployed into the measurementwater, and can measure to a depth of 30 m or less.On models U-52G and U-53G, the controller has aGPS function for logging position data withmeasurement data. The display screen providesoperating guidance in addition to a display of allmeasurement parameters.Control Unit1. IntroductionMeasurements of water properties such as watertemperature, conductivity, pH, dissolved oxygen,turbidity, etc. are important to performenvironmental water monitoring, maintenanceand control of supply and sewage water, andwastewater inspections at construction sites andfactories. However, using separate instrumentsfor each measurement can be cumbersome. Thus,a multi-parameter water quality checkers such asU-20 are often used to perform thesemeasurements.A multi-parameter water quality checkerintegrates all the sensors for measuring turbidity,dissolved oxygen, pH, conductivity, ORP, waterdepth, and temperature in a single handheld unit.However, few multi-parameter water qualitycheckers are equipped with a turbidity meterwhich requires an optical sensor. The turbiditysensors are influenced by air bubbles and dirt,resulting in unstable measurements. In addition,the replacement of sensor film on the dissolvedoxygen sensor tends to be difficult.In this study, new multi-parameter water qualitychecker which can figure out the former U-20drawback was developed.2. Instrument OverviewFigure 1 shows the appearance and displayscreen of the multi-parameter water qualityTurbiditySensorFig.1 Appearance and Display of U-50Dissolved OxygenConductivitypHORPWater Depth ・TemperatureProbeFig.2 Sensors Housed in Sensor ProbeFigure 2 shows the sensors in the sensor probe.The seven sensors for measuring turbidity,

dissolved oxygen (DO), pH, conductivity, ORP,water depth, and temperature is embedded into10-cm diameter probe base. The sensors forturbidity, DO, pH, and ORP are removable andeasy to replace.Membrane Cap3. Comparison of the U-20 and U-50Table 1 compares the specifications of the U-20and newly developed U-50 series. As shown in thetable, improvements were also made to eachmeasurement parameter. Significantimprovements were made particularly in theturbidity meter and dissolved oxygen electrode.The turbidity meter in the U-20 uses an LED asthe light source with a 30 degree scatteringmethod. Meanwhile, the U-50 series model U-53uses a tungsten lamp as the light source with a 90degree scattering method. This method complieswith the US EPA Method 180.1, and is strongagainst chromaticity differences while beinghighly sensitive to small particles. Prior to themeasurement, the wiper can clean the sensorwindow to reduce the influences of air bubblesand dirt.The dissolved oxygen sensor on the U-50 is basedon the polarographic method, whereas on theU-20 the galvanic battery system. This means theelectrode can be lead-free, making it exempt ofrestrictions imposed by the European RoHSregulation. As shown in Figure 3, the oxygenisolation film is shaped like a cap. This allows thecustomer to replace the film simply by tighteningthe film cap. Additionally, the measurementrange was expanded.Table 2 shows potential new measuringapplications for the U-50 series afforded by theseimprovements. The improved turbiditymeasuring accuracy enables measurement andcontrol of ground water, environmental water,and plant water with low turbidity. Turbiditysensors in previous multi-parameter waterquality checkers are not capable of measuring lowturbidity concentrations. Users who accustomedto measuring turbidity separately will appreciatethe simplified and simultaneous measurement.The expanded measuring range for dissolvedoxygen enables measurement and control of highconcentrations of oxygenated water such asoxygen enriched drinking-water and thephotosynthetically-activated environment water.The expanded measuring range for conductivityenables measurement of high salinity samplessuch as seasonings solution in the food makingindustry.DO Sensor Main BodyFig.3 Structure of DO Sensor4. Measurement ExamplesThe changes in turbidity and dissolved oxygen asmeasured continuously over 12 days in Inba-pond,Chiba prefecture is shown in Figure 4. When webegan measuring on May 28, the turbidity was20.5 NTU and the COD value was 10.0 ppm. Theturbidity and COD value dropped during themeasurement period and became 5.89 NTU and8.8 ppm, respectively, on the last day of June 9.This result suggests decrease in organic matter.The dissolved oxygen (DO) concentrationincreased from the morning to the afternoon, anddecreased from the evening to the followingmorning. This is the result of oxygen generated byphotosynthesis in the afternoon, and oxygenconsumed by breathing during thenight.Although traces of organic matter werefound on the measurement unit after 12 days ofcontinuous measurement, the wiper kept the cellwindow on the turbidity meter in a clean state.

Tab.1 Specifications and Improved Points of U-20 andU-50 SeriesParts name Item U-20 Series U-50 Series Improved PointsSensor Probe Measurement temperature 0~55℃ -5~55℃ Measurable low temperature sampleBacklightingLCDCustum(monochrome) Graphic LC(monochrome) Multiple parameters listed on Screen1 parameter listed on Screen 11 parameter listed on Screen Equipped with backlightingControl UnitMagnified view of display valueData memory 2880 100001 day's data acquisition at intervals of 10seconds通 信 RS232 USB (peripheral) speeding up of data movement to PCpHOxidationReducitonPotential(ORP)DissolvedOxygen(DO)Conductivity(COND)SalinityTotal DissolvedSolid(TDS)Seawaterspecific gravityσ t、σ 0、σ 15TemperatureTurbidity(TURB)Water DepthMeasurement principleRangeResolutionRepeatabilityAccuracyMeasurement principleRangeResolutionRepeatabilityAccuracyGlass electrode methodpH0 to 140.01pH±0.05pH±0.1pHPlatinum electrode method-2000mV to +2000mV1mV±5mV±15mVMeasurement principle Galvanic method Polarographic methodRange 0 to 19.99 mg/L 0 to 50.00 mg/LResolutionRepeatabilityAccuracy0.2 mg/L0.01mg/L±0.1mg/L0~20 mg/L:±0.2mg/L20~50 mg/L:±0.5mg/LMeasurement principleRange 0 to 9.99 S/m4 AC electrode method0 to 10 S/mResolutionRepeatability ±1 %F.S.0.1 %F.S.±0.5 %F.S.Accuracy ±3 %F.S. ±1 %F.S.Measurement principleConductivity coversionRange 0 to 4% 0 to 70 PPTResolutionRepeatabilityAccuracyMeasurement principleRangeResolutionRepeatabilityAccuracyMeasurement principleRangeResolutionRepeatabilityAccuracyMeasurement principleRange 0 to 55℃0.1PPT(0.01%)±1PPT(0.1%)±3PPT(0.3%)Conductivity coversion0 to 100 g/L0.1%F.S.±2 g/L±5 g/LConductivity coversion0 to 50 σt0.1σt±2 σt±5 σtThermistor method-5 to 55℃ResolutionRepeatability ±0.3℃0.01℃±0.1℃(at calibration point)Measurement principleLED light sourceTungsten lamp sourceScattering Method 90°scattering method (U-53)Range 0 to 800 NTU 0 to 1000 NTUResolution 0.1 NTU 0.01 NTURepeatability±3 %F.S.±3 %(Reading) orAccuracy±5 %F.S.Tab.2 New Applications Possible with the U-50 SeriesFeatures of the U-50New applicationsImproved turbidity accuracy±0.1NTU whichever is greater0 to 10NTU:±0.5NTU10 to 1000NTU:±3 %(Reading) or±1NTU whichever is greaterMeasurement principlePressure methodRange 0 to 100m 0 to 30mResolution 0.1m 0.05mRepeatability ±3%F.S. ±1%F.S.Accuracy ±5%F.S. ±0.3mMeasurement and control of low turbidity ground water,environmental water, supply water, and plant water.Expanded measurement range for Control of high concentrations of oxygenated waterdissolved oxygen(beverages, envirionment water)Expanded measurement range for High salinity concentrations (seasonings, factory wastewater,conductivityetc.)Lowering running cost by chipping pH andReference SensorLowering running cost by chipping ORPSensorcalibration by ORP Standard SolutionSafety inner Solution (KCl solution)Easy maintenance by DO membrane CapLead-free componentmesurable saturated oxygen solutionAccuracy improvement by 4 pointcalibrationMeasurable doubled general seawaterSalinityRepeatability improvementThe wiper can clean the sensor window toreduce the influences of air bubbles and dirt.U-53 uses a tungsten lamp as the lightsource with a 90 degree scattering method.This method complies with the US EPAMethod 180.1.Accuracy improvement by New pressuresensor

Turbidity(NTU)50454035302520151055 月2824/172917/143014/123123/13TurbidityDO6 月121/17216/1505/28 5/30 6/1 6/3Date6/5 6/7 6/9322/14Fig.4 Continuous Test Data of Turbidity and DO in424/17Lake ImbaFigure 5 shows the measurement results for pHand ORP. On sunny days during the continuoustesting period, the pH values shifted to alkaline.This result suggests that photosynthesis of plantscaused the carbon dioxide gas and organic matterin the lake to drop. On the other hand, the ORPshifted to the reducing side, suggesting that theeffects of water purification induced byphotosynthesis.10.05 月2824/172917/143014/123123/136 月121/17216/15322/14424/17523/15523/15625/18625/18726/19726/19822/19822/19922/20922/20876543210500DO(mg/L)immersion direction changed over a range of 0.0NTU to 1.0 NTU. Measuring in the retractiondirection from 20 m to 10 m showed a significantchange from 0.0 NTU to 5.0 NTU, revealing adiscrepancy with the measurement in theimmersion direction. This suggests that airbubbles occurred on the measuring unit due todecompression and temperature rise. On theother hand, the U-53 turbidity meter, equippedwith a wiper, showed consistent results between0.3 NTU and 0.8 NTU, in both immersion andretraction directions. This result indicates thatthe wiper on the new turbidity meter effectivelycancels the effects of air bubbles.Turbidity(NTU)6543210Turbidity of U-53(Lower)Turbidity of U-20(Lower)Turbidity of U-53 (raised)Turbidity of U-20 (raised)0 10 20 30Water Depth(m)Fig.6 Turbidity immersion test in Lake MotosupH9.59.08.58.07.5pHORP450400350300250200150ORP(mg/l)5. ConclusionThe newly developed U-50 features EPAMethod 180.1 compliant turbidity sensor,expanded measurement ranges and greaterease of handling. These features can expandthe scope of an existing multi-parameter waterquality checker.7.05/28 5/30 6/1 6/3 6/5 6/7 6/9Date100Fig.5 Continuous Test Data of pH and ORP in LakeImbaFigure 6 shows the results of measurements inMotosu Lake, Yamanashi prefecture. In thismeasurement, the same test was performed usingthe turbidity meter on the former model U-20(30-degree transmission scattering method),which does not have a wiper. On the U-20turbidity meter, the measurement in the