Transcript Document

pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
CONTROLS
Concerns in pH # 6:
High Purity pH
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
PROBLEM
High purity water has a very high impedance. The high
impedance of the water combined with the high
impedance of the glass measuring electrode makes the
pH signal susceptible to electrostatic interference and
sluggish response.
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
Solution
Model 615-25 high purity pH panel or model 615-26
ultra-high purity (less than 1 µScm-1) panel
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
pH Tip Configuration
Reference
Flat Glass
Stem
Reference
Junction
SS Flow cell
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
pH Tip Configuration
•Flat surface reduces path length between glass and
reference for reduced impedance
•Flat surface allows small volume at electrode tip
•Flat surface close to inlet allows fast sample response
•Stainless Steel flow cell can be used for differential
measurement technique and eliminate electrostatic
pickup.
•Use low conductivity buffers for quicker response after
calibration
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
Short path length between the glass and the
reference minimizes impedance and will speed
response time.
1 mm separation
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
Small sample volume at the tip allows fast sample turnover.
Also, connection between the glass and reference is
accomplished by KCl that leaches into the sample from the
reference. The smaller the sample volume, the better the
connection between the glass and reference .
1 ml volume at
sensor tip
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
Ultra-high purity applications are susceptible to electrostatic
interference. The model 615-26 has a differential pre-amplifier
which uses the stainless steel flow cell as a third electrode.
The differential pre-amp measures the mV potential between
the glass and flow cell and then the reference and flow cell
and subtracts the two values. Thus, the electrostatic
interference is eliminated from the measurement.
mV
measurement
between glass
and flow cell
then reference
and flow cell.
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
Pressure and Flow
Fluctuating pressure and flow will have an effect
on the stability of the pH measurement. As the
KCl from the reference is the conductor,
fluctuation of the pressure or flow will allow
varying amounts of KCl to flow out of the
reference. The varying flow will be read by the
pH electrode as varying conductivity and the pH
meter will show “jumpy” readings.
Pressure and flow regulation is standard for
both the 615-25 and 615-26 to create better pH
stability.
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IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
Calibration
When calibrating, it is important to use the
proper standards for best accuracy and quick
response. As the conductivity of the sample is
low, if normal pH buffers are used they will be
absorbed into the reference junction and take a
long time to to purged. By using low
conductivity buffers, excellent accuracy and
speed of response will be accomplished after
calibration.
www.iccontrols.com
IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
Calibration and Response Time
11
10
pH
9
8
Standard Buffer
7
Low Conductivity
Buffer
6
5
4
0
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30
60
90
Time (Minutes)
180
IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
IC Controls High Purity pH
Low sample volume
Short path length between the glass and
reference
Differential measurement in ultra-pure
applications
Pressure and flow regulation
Low conductivity buffers available
Proven Technology
Superior Design
Better Results
www.iccontrols.com
IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS
pH / ORP
Conductivity
Dissolved Oxygen
Chlorine
Standards
615 Sensor and Flow cell
For more information:
Call:
519-941-8161
800-265-9161
Email: [email protected]
or www.iccontrols.com
We will be happy to help
you directly or put you in
contact with your local
Representative of IC Controls
Qualitiy Water Products
615-26
www.iccontrols.com
IC Controls Quality Water Solutions for pH
R1.0 © 2004 IC CONTROLS