Theory of Liquid Measurements Theory of Liquid Measurements - PowerPoint PPT Presentation

Theory of Liquid Measurements Theory of Liquid Measurements Conductivity/Resistivity • Conductivity/Resistivity • pH • pH • ORP • ORP • THORNTON / METTLER TOLEDO

Ionic Conductance Ionic Conductance ~ ~ Na + + Na - - + H + H O O H H H H Cl - - Cl O O H H THORNTON / METTLER TOLEDO

Cell Constant Cell Constant 1 cm 1 cm 1 cm 1 cm 1 cm 1 cm Length 1 cm Length 1 cm -1 Conductivity Cell Constant = = = 1 cm -1 Conductivity Cell Constant = = = 1 cm 2 1 cm 2 Area Area 1 cm THORNTON / METTLER TOLEDO

Other Cell Constants Other Cell Constants 1cm 1cm 10cm 1cm 0.1cm 1cm 0 .1constant 1 0 .0constant Cell Constant = Multiplier THORNTON / METTLER TOLEDO

Resistivity/Conductivity Cell Resistivity/Conductivity Cell Concentric Electrodes OUTER ELECTRODE INSULATOR INNER ELECTRODE THORNTON / METTLER TOLEDO

Units of Conductivity/Resistivity Units of Conductivity/Resistivity Resistance ohm Resistance ohm Conductance mho, siemens = 1/ohm Conductance mho, siemens = 1/ohm Resistivity ohm-cm, Resistivity ohm-cm, Ω -cm Ω Ω Ω -cm, M Ω Ω Ω Ω megohm-cm, M -cm megohm Conductivity mho/cm, Conductivity mho/cm, µ µ µ µ mho/cm µ µ µ µ mho/cm siemens/cm, siemens/cm, /cm, µ µ S/cm µ µ µ µ µ µ microsiemens/cm, S/cm microsiemens THORNTON / METTLER TOLEDO

Units of Conductivity/Resistivity Units of Conductivity/Resistivity Industry Preferences: Industry Preferences: Resistivity - Semiconductor ultrapure water Resistivity - Semiconductor ultrapure water Conductivity - Power, Pharmaceutical, Conductivity - Power, Pharmaceutical, Pretreatment stages, Cooling towers, Pretreatment stages, Cooling towers, Wastewater Wastewater Total Dissolved Solids (ppm TDS) Total Dissolved Solids (ppm TDS) THORNTON / METTLER TOLEDO

Cell Constant Traceability Cell Constant Traceability ASTM D1125 ASTM D1125 Production Cell Production Cell Standards Lab Primary Standard Primary Standard Standards Lab Constant Constant and Pure Water Cell Constant and Pure Water Cell Constant at 15, 25, 40 ° ° C at 15, 25, 40 C THORNTON / METTLER TOLEDO

Ultrapure Water Sensor Ultrapure Water Sensor Calibration/ Certification System Calibration/ Certification System Thornton Inc. THORNTON / METTLER TOLEDO

Conductivity, Resistivity, TDS Ranges Conductivity, Resistivity, TDS Ranges 100M 10M 1M 100K 10K 1K 100 10 1 Resistivity ohm-cm Ultrapure water Deionized water Distilled water Condensate Drinking water Cooling tower water Percentage of acids, bases and salt Waste water Brackish water, Sea water Water for Industrial Process 5% Salinity 2% NaOH 20% HCl µS-cm Conductivity 0.01 .1 1 10 100 1000 10k 100k 1000k ppm 0.021 0.4 4.6 46 460 4.6k TDS Conductivity and resistivity are measured at 25 ° ° ° ° C; TDS is expressed as Sodium Chloride (NaCl) THORNTON / METTLER TOLEDO

On-Line Conductivity Sensor On-Line Conductivity Sensor Calibration/Verification Calibration/Verification on-line instrument in-line cell Process flow calibrated reference instrument sample take-off factory-certified reference cell flow chamber 200-500 mL/min sample flow to drain THORNTON / METTLER TOLEDO

Temperature Effects on Conductivity Temperature Effects on Conductivity ~ ~ Na + + Na - - H + + H O O H H H H - Cl - O Cl O H H THORNTON / METTLER TOLEDO

Conductivity/Resistivity Conductivity/Resistivity Temperature Coefficients Temperature Coefficients Natural waters, etc. Natural waters, etc. (>2 µ µ µ S/cm) µ µ µ µ µ S/cm) ~ 2 %/°C (>2 ~ 2 %/°C High purity water High purity water (0.055 µ µ µ µ µ S/cm or 18.2 µ µ µ S/cm or 18.2 Megohm Megohm-cm) -cm) 4 - 7 %/°C 4 - 7 %/°C (0.055 THORNTON / METTLER TOLEDO

Dissociation of Water Dissociation of Water H + + H H + + H O 2- 2- O O 2- 2- O + H + H + H + H + + OH - H 2 O H + + OH - H 2 O H THORNTON / METTLER TOLEDO

Conductivity of Pure Water vs. Temperature Conductivity of Pure Water vs. Temperature Conductivity (µS/cm) Resistivity (M � -cm) 100 0.01 10 0.1 1 1 0 10 20 30 40 50 60 70 80 90 100 Temperature (°C) THORNTON / METTLER TOLEDO

Conductivity vs. Temperature Conductivity vs. Temperature 10.00 NaCl Concentration 4390 ppb Conductivity (µS/cm) 1730 ppb 1.00 840 ppb 395 ppb 129 ppb 0.10 40 ppb 0 ppb 0.01 0 10 20 30 40 50 60 70 80 90 100 Temperature (°C) THORNTON / METTLER TOLEDO

Temperature Compensation Temperature Compensation • Standard -- high purity water with mineral contamination • Linear, %/°C -- special applications with known coefficient • Cation/Ammonia/ETA -- power plant cycle chemistry and semiconductor acid etch rinse operations • Alcohol -- special semiconductor rinse operations • Glycol -- semiconductor coolant monitoring • Light 84 -- same as Standard but with 1984 pure water data (reads slightly higher resistivity) • Direct % Concentration Readout of HCl, H 2 SO 4 , NaOH automatically selects appropriate compensation THORNTON / METTLER TOLEDO

Cell Installation Cell Installation Recommended Cell Installation... OUTLET INLET Flow should be directed at the end of the sensor THORNTON / METTLER TOLEDO

High Conductivity Measurements • Applications • Reverse Osmosis feedwater • Acid/Base deionizer regenerant concentration • Process fluids • Recycle water • Wastewater/effluent • Cooling towers • Conductivity Measurement Technologies • Two-electrode contact • Four-electrode contact • Inductive (non-contact, electrodeless, toroidal) THORNTON / METTLER TOLEDO

Conductivity vs. Concentration 0.9 0.8 0.7 HCl H2SO4 0.6 Conductivity (S/cm) 0.5 NaOH 0.4 0.3 0.2 NaCl 0.1 0 0 10 20 30 40 50 60 70 80 90 100 Concentration (% by weight) THORNTON / METTLER TOLEDO

Two-Electrode Conductivity Measurement 50/cm Constant Cell Graphite Bottom view Electrodes THORNTON / METTLER TOLEDO

Two-Electrode Conductivity Measurement 10/cm Constant Cell Sheath Slot RTD Graphite Bottom view Electrodes THORNTON / METTLER TOLEDO

Four-Electrode Conductivity Measurement Four-Electrode Measuring Instrument AC Current Source AC Voltage Measurement Measuring Electrodes Four Electrode Sensor Drive Electrodes THORNTON / METTLER TOLEDO

Four-Electrode Conductivity Measurement Four-electrode sensors and instruments can tolerate poor measuring conditions due to three factors: 1. Electrode metal surface condition is less important. 2. Electrode fouling or coating has much less effect. 3. Four-electrode sensors do not have the narrow channels of high, two-electrode cell constants. The resulting flat surface design is much less vulnerable to fouling. THORNTON / METTLER TOLEDO

Inductive Conductivity Measurement Energized Measured Inductive (non-contact, electrodeless, toroidal) Conductivity Sensor THORNTON / METTLER TOLEDO

Inductive Conductivity Measurement • Virtually non-fouling • No metal/solution contact • Reliable high conductivity measurements • Relatively large sensor size • Cell constant can be affected by surrounding pipe THORNTON / METTLER TOLEDO

pH Range pH Range THORNTON / METTLER TOLEDO

pH Measurement pH Measurement Dissociation of water Dissociation of water + + OH - H 2 O H + + OH - H 2 O H + ] - ] [H + [OH - K w = ] ] K = [H [OH w THORNTON / METTLER TOLEDO

pH Scale pH Scale + ] pH ~ -log 10 [H + ] pH ~ -log 10 [H + ] ~ 10 -pH [H + ] ~ 10 -pH [H 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH -14 [H + ] -0 10 -1 10 -2 10 -3 10 -4 10 -5 10 -6 10 -7 10 -8 10 -9 10 -10 10 [H + ] 10 -0 10 10 -1 10 -2 10 -3 10 -4 10 -5 10 -6 10 -7 10 -8 10 -9 10 -10 10 -11 -11 10 10 -12 -12 10 10 -13 -13 10 10 -14 -0 [OH -14 10 -13 10 -12 10 -10 10 -9 10 -8 10 -7 10 -6 10 -5 10 -4 10 -3 10 -2 10 -1 10 [OH + + ] ] 10 -14 10 -13 10 -12 10 -11 -11 10 10 -10 10 -9 10 -8 10 -7 10 -6 10 -5 10 -4 10 -3 10 -2 10 -1 10 -0 10 at 25°C at 25°C THORNTON / METTLER TOLEDO

Conductivity vs vs pH pH Conductivity Conductivity Base Acid 0.055 µS/cm 18.2 M Ω Ω -cm Ω Ω 7 pH THORNTON / METTLER TOLEDO

Conductivity vs vs pH pH Conductivity THORNTON / METTLER TOLEDO

pH vs. Temperature for Pure Waters pH vs. Temperature for Pure Waters 11 10 9 0.5 ppm NH3 pH 8 7 Pure Water 6 0 10 20 30 40 50 60 70 80 90 100 Temperature (°C) THORNTON / METTLER TOLEDO

pH Electrode System pH Electrode System To Measuring To Measuring Circuit Circuit Temperature Temperature Reference Reference Glass pH Glass pH Compensator Compensator THORNTON / METTLER TOLEDO

Combination pH Electrode Combination pH Electrode Electrolyte RTD (insulated) Reference junction Measuring membrane THORNTON / METTLER TOLEDO

pH Electrode Output pH Electrode Output 50°C 25°C 400 100°C 0°C 200 mV 0 -200 -400 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH THORNTON / METTLER TOLEDO

pH Temperature Compensation pH Temperature Compensation Solution Adder (standardize Temperature offset, asymmetry) Coefficient Multiplier (slope) pH 25°C Electrode mV Nernst Electrode Solution pH T Temperature Temperature Temperature Compensation Compensation THORNTON / METTLER TOLEDO