Transcript Document

pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
CONTROLS
Concerns in pH # 4:
Reference
Contamination
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
PROBLEM
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
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
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.
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
Typical pH Electrode Internal
Silver/Silver Chloride
Wire
Potassium Chloride (KCl)
Internal Fill Solution
Porous Frit
Solid Spool Piece
Porous Reference
Junction
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
Contamination with Standard Internal
With no protection in the
reference the KCl and
Silver/Silver Chloride
wire becomes
contaminated very
quickly.
Process
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
Contamination with Double
Junction Internal
By adding the Double
Junction, the path length
is increased and the rate
of contamination is
decreased.
Process
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
Contamination with Plasticized
Internal
By adding the Plasticized
Reference, which is solid
up to 150oC, the
migration is slower
because it will take
longer to migrate through
a solid in comparison to a
liquid.
Process
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
Contamination with Double Junction
and Plasticized Internal
Process
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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.
IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
IC Controls Plasticized, Double
Junction Reference
Longer Path Length
Slower Migration
Solid up to 150oC
Longer Sensor Life
Proven Technology
Superior Design
Better Results
www.iccontrols.com
IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS