IC Controls Quality Water Solutions for pH pH / ORP Conductivity Dissolved Oxygen Chlorine Standards R1.0 © 2004 IC CONTROLS Concerns in pH # 4: Reference Contamination CONTROLS

IC Controls Quality Water Solutions for pH pH / ORP Conductivity Dissolved Oxygen Chlorine Standards R1.0 © 2004 IC CONTROLS pH electrodes have porous reference junctions which allows KCl to migrate through the junction to complete the electrochemical connection and cause a mV signal to be produced. Since the junction is porous the process can also migrate into the reference causing reference contamination and premature failure of the pH electrode PROBLEM

IC Controls Quality Water Solutions for pH pH / ORP Conductivity Dissolved Oxygen Chlorine Standards R1.0 © 2004 IC CONTROLS CAUSE As the process migrates into the reference it attacks the Silver/Silver Chloride wire changing the chemistry which results in the electrode drifting. This is seen as an offset from zero mV during calibration.

IC Controls Quality Water Solutions for pH pH / ORP Conductivity Dissolved Oxygen Chlorine Standards R1.0 © 2004 IC CONTROLS Silver/Silver Chloride Wire Porous Frit Solid Spool Piece Porous Reference Junction Potassium Chloride (KCl) Internal Fill Solution Typical pH Electrode Internal

IC Controls Quality Water Solutions for pH pH / ORP Conductivity Dissolved Oxygen Chlorine Standards R1.0 © 2004 IC CONTROLS Process With no protection in the reference the KCl and Silver/Silver Chloride wire becomes contaminated very quickly. Contamination with Standard Internal

IC Controls Quality Water Solutions for pH pH / ORP Conductivity Dissolved Oxygen Chlorine Standards R1.0 © 2004 IC CONTROLS Process By adding the Double Junction, the path length is increased and the rate of contamination is decreased. Contamination with Double Junction Internal

IC Controls Quality Water Solutions for pH pH / ORP Conductivity Dissolved Oxygen Chlorine Standards R1.0 © 2004 IC CONTROLS Process By adding the Plasticized Reference, which is solid up to 150 o C, the migration is slower because it will take longer to migrate through a solid in comparison to a liquid. Contamination with Plasticized Internal

IC Controls Quality Water Solutions for pH pH / ORP Conductivity Dissolved Oxygen Chlorine Standards R1.0 © 2004 IC CONTROLS Process By combining the Double Junction and the plasticized Reference, the path length is increased and the rate of contamination is decreased which will give maximum life in applications where reference contamination is a problem. Life expectancy can be months longer when this combination is used. Contamination with Double Junction and Plasticized Internal

IC Controls Quality Water Solutions for pH pH / ORP Conductivity Dissolved Oxygen Chlorine Standards R1.0 © 2004 IC CONTROLS IC Controls Plasticized, Double Junction Reference Longer Path Length Slower Migration Solid up to 150 o C Longer Sensor Life Proven Technology Superior Design Better Results