What is ph? ph is the measurement of the Hydrogen Ion concentration in a particular solution. Indicates the Acidity or Alkalinity of a solution.

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1 What is ph? ph is the measurement of the Hydrogen Ion concentration in a particular solution. Indicates the Acidity or Alkalinity of a solution. Why is ph measured? Used as a process control parameter. Most reliable specific Ion measurement. Least maintenance intensive specific Ion measurement.

2 ph = - Log [H + ] What is ph? Acid Neutral Base H OH ph Scale

3 The ph Measurement ph Measuring Components Measuring Electrode Reference Electrode Temperature Compensator Analyzer (Transmitter) How the Measuring System works The glass electrode develops a potential directly related to the Hydrogen Ion concentration of a solution. The potential is measured as (mv) across the glass membrane. The Reference electrode is necessary as a constant potential for comparison against the measuring electrode. It also completes the electrical circuit - Provides liquid wire! The change in voltage/hydrogen Ion concentration will be directly proportional to the change in ph.

4 ph Simplified! ph system works similar to battery - The Glass electrode provides a constant voltage (steady state), while the reference builds resistance with time/usage. As Reference electrode ages the internal resistance (across Junction) increases Resistance across Junction increases until measurement signal lost - High Impedance! After initial calibration, 90% or more of calibration offset is due to reference deterioration. V = IR V = Constant Voltage Potential V = Glass electrode output R = Reference electrode

5 Measuring Electrodes Glass: Most Common - Used in 95% or more of all applications. Glass Electrode Antimony Electrode Antimony - Silver white metal (Similar to Lead). Used in applications where glass will not! Example: (HF) Used in 1%- 2% of all applications. Solid State - Utilizes a Solid State Chip rather than glass. Example: ISFET Technology - Currently used in 2%-3% of all applications Solid State Electrode

6 Glass Measuring Electrode Coaxial Cable Ag/AgCl Electrode High Impedance Glass Membrane H + KCl Electrolyte H + H +

7 Durafet ph Electrode Low Impedance Connector Quick Disconnect Cable Ag/AgCl Element Fast Responding Temperature Sensor Replaceable Ceramic Reference Junction Refillable Saturated KCl Gel Rugged Durafet Sensor Counter Electrode

8 Troubleshooting the Electrode System Reference electrode is the weak link in the measurement system in 90% of all applications Reference open to the process - porous junction Typical modes of reference failure: Plugging Fouling Poisoning Depletion Pressure spikes

9 Reference Electrodes l Diffusion (Slurry/Gel) - Used in 95% or more applications Single Junction Double Junction Triple Junction Single Junction Flowing - Used in 5% or less applications Salt Bridge Bellowmatic Double Junction Triple Junction Non-Porous Reference Solution ground Ceramic body Solid State - Currently unavailable Ion Sensitive Coating

10 Reference Electrode Selection Guide Problem Plugging Fouling Poisoning Depleting Pressure Initial Junction Type Cost Ease of Use Long Term Costs DIFFUSION JUNCTION REFERENCE ELECTRODE Single Junction Double Junction Triple Junction FLOWING JUNCTION REFERENCE ELECTRODE Salt Bridge Bellomatic Solid State l RANKING: 1=GOOD 2= FAIR 3==POOR

11 Reference Electrode Diffusion Type Standard Wire Ag/AgCl Electrode Cl - K + Saturated KCl Electrolyte Gel K + Cl - Porous Junction K + Cl - mv Junction Potential offset during calibration (Asymmetry)

12 Double Junction Reference Electrode Diffusion Type Standard Wire Ag/AgCl Electrode Internal Junction No Silver Ion Porous Junction K + Cl - Ag + K + Cl - K + Cl - Saturated KCl Electrolyte Gel Saturated KCl Electrolyte Gel

13 Triple Junction Reference Electrode Diffusion type Standard Wire Ag/AgCl Wire Internal Junction No Silver Ion Porous Junction K + Cl - Ag/AgCl K + Cl - Cl- Cl - Cl - K + Cl - K + K + Saturated KCL Electrolyte Gel Saturated KCL or Ammonium Nitrate Electrolyte Gel

14 Reference Electrode Flowing Type Standard Wire Ag/AgCl Electrode To Reservoir K + Cl - 2 Normal KCl Electrolyte Flowing Junction K + Cl -

15 Reference Rules of Thumb Typical Applications - Expect to replace (3) Reference electrodes for every (1) Measuring Harsh Applications - Expect to replace (10) Reference electrodes for every (1) Measuring Minimum Life expectancy - Junction Poisoning Symptoms to be aware of: Severe discoloring of Junction Junction turns brown or black in color Discoloration not removed when cleaned Remember - When in doubt think... Reference! Reference! Reference!

16 The Bellowmatic electrode Flowing Junction Internally pressurized by bellows assembly Pressure compensating Bellows floats with process pressure changes Self contained No external connections/tubes/reservoirs Unique to the industry One of a Kind!

17 The Bellowmatic Solution What problems can the Bellowmatic solve? Plugging Positive pressure prevents internal build-up. Fouling Positive pressure prevents external build-up. Poisoning Positive pressure prevents process migration. Depletion Positive pressure prevents dilution. Pressure Spikes Floating bellows compensates for process spikes.

18 Where each Reference electrode type could operate (%) All ph Applications Single Double Triple Salt Bridge Bellowmatic Solid State

19 Where each Reference electrode type should operate (%) 100 Solid State Flowing - Salt Bridge 70 Flowing - Bellowmatic 60 Diffusion - All types All ph Applications

20 Test Questions ph 1) What should the output (Millivolts) of a ph measuring electrode be in a 7 buffer? 2) What should the Asymmetry of a new reference electrode be after calibration? 3) In a typical application how many reference electrodes will be replaced per glass electrode? 4) What is the reference mode of failure that causes the junction to turn brown or black? 5) What company makes an electrode like the Bellomatic? 6) What are two applications ideal for using the Bellomatic? CONDUCTIVITY 7) What Rule of Thumb value (us/cm) defines when to use Inductive vs. Contacting conductivity? 8) What factor is used to convert from us/cm to umho/cm? 9) What two industries were DC400 designed for? 10) What other companies make Dual cell analyzers? 11) How many bore sizes are available for the IC40 sensor? 12) Why is the IC40 stable with process temperature changes? 13) The 5X5 matrix is compensating for what effect on the solution? match the analyzer/measuring technology that should be used with the following applications: a = DC; b = SC; c = IC 14) Reverse Osmosis system 15) Demineralizer Regeneration System 16) Softener 17) Demineralizer Outlet ZIRCONIA OXYGEN 18) Why is our cell resistant to attacks from flue gases? 19) How does the competition bond the platinum to their ceramic cells. 20) What are two advantages of using reference air as one of the calibration gases?

21 Test Questions ph 1) What should the output (Millivolts) of a ph measuring electrode be in a 7 buffer? (Zero Millivolts) 2) What should the Asymmetry of a new reference electrode be after calibration? ( + or - 20 Millivolts) 3) In a typical application how many reference electrodes will be replaced per glass electrode? (3 to 1) 4) What is the reference mode of failure that causes the junction to turn brown or black? (Poisoning) 5) What company makes an electrode like the Bellomatic? (None) 6) What are two applications ideal for using the Bellomatic? (Students Choice) CONDUCTIVITY 7) What Rule of Thumb value (us/cm) defines when to use Inductive vs. Contacting conductivity? (100 us/cm) 8) What factor is used to convert from us/cm to umho/cm? (None - both units have same value) 9) What two industries were DC400 designed for? (Power & Semiconductor) 10) What other companies make Dual cell analyzers? (Rosemont, L&N, Thornton, Foxboro, Signet) 11) How many bore sizes are available for the IC40 sensor? (One) 12) Why is the IC40 stable with process temperature changes? (Matched Coils) 13) The 5X5 matrix is compensating for what effect on the solution? (Temperature) match the analyzer/measuring technology that should be used with the following applications: a = DC; b = SC; c = IC 14) Reverse Osmosis system (DC or a) 15) Demineralizer Regeneration System (IC or C) 16) Softener (DC or a) 17) Demineralizer Outlet (SC or b) ZIRCONIA OXYGEN 18) Why is our cell resistant to attacks from flue gases? (Molecular Bonding) 19) How does the competition bond the platinum to their ceramic cells. (Adhesive Bonding) 20) What are two advantages of using reference air as one of the calibration gases? (Cost and true zero of cell output)