user manual conductivity sensor

user manual conductivity sensor
USER MANUAL
CONDUCTIVITY SENSOR
um-400SR2
404 General Purpose
402 Pure Water Conductivity
425 Universal
403 Ball Valve Retractable
405 Easy Clean
401 Hot Condensate
Contents
IC Controls
Contents
um-400SR2
Contents............................................................................................................................................2
CONDUCTIVITY MEASUREMENT.............................................................................................3
What is conductivity?..................................................................................................................3
Cell Constant...............................................................................................................................4
Temperature Compensation.........................................................................................................5
Sensor Cleaning...........................................................................................................................6
Calibration...................................................................................................................................6
Conductivity Calibration Theory.................................................................................................6
Selecting Conductivity Sensors...................................................................................................8
INSTALLATION............................................................................................................................10
Selecting the Location...............................................................................................................10
Analyzer Location.....................................................................................................................10
Sensor Mounting........................................................................................................................10
Typical Flow Mounting.............................................................................................................11
Typical Insertion Mounting.......................................................................................................11
Typical Submersion Mounting..................................................................................................12
Sensor Wiring............................................................................................................................12
Connections...............................................................................................................................13
INSTRUMENT SHOP TESTS.......................................................................................................14
Checking The Sensor.................................................................................................................14
Preparation For Use...................................................................................................................14
Testing With The Analyzer.......................................................................................................14
CONDUCTIVITY CALIBRATION..............................................................................................15
Selecting a Standard..................................................................................................................15
Temperature Dependence of Standards.....................................................................................15
Other Standards or Custom Standards.......................................................................................15
Where to do Conductivity Calibrations.....................................................................................16
Calibration Using Standards......................................................................................................16
Grab-Sample Calibration...........................................................................................................17
SENSOR MAINTENANCE...........................................................................................................18
Sensor Insertion.........................................................................................................................18
Removal of 403 Ball Valve Sensor...........................................................................................18
Sensor Storage...........................................................................................................................18
Monthly Maintenance................................................................................................................18
Yearly Maintenance...................................................................................................................19
When To Clean The Sensor.......................................................................................................19
Troubleshooting Hints...............................................................................................................19
Chemical Cleaning of Sensor....................................................................................................21
CONDUCTIVITY SENSORS........................................................................................................22
DRAWINGS...................................................................................................................................23
D5920095; Sensor Wiring.........................................................................................................23
GLOSSARY....................................................................................................................................24
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um-400SR2
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CONDUCTIVITY MEASUREMENT
Conductivity Terminology and
Formulas
CONDUCTIVITY
MEASUREMENT
conductivity = Kcell 100 – kTC (25.0 – TTC)
R
100
What is conductivity?
Electrolytic conductivity is a measure of
the ability of a solution to carry a current.
In the 1980's, international agreement
adopted the basic unit of electric
conductance as siemens (S), and it is
defined as the reciprocal of the resistance
in ohms of a 1 cm cube of the liquid at a
specified temperature.
The units of
measurement are the reciprocal of ohm/cm,
which was expressed as mho/cm. This was
usually expressed in millionths of a
mho/cm or simply µmho. North American
practice historically used µmho units, now
renamed microsiemens (µS/cm).
Current flow in liquids differs from that in
metal conductors in that electrons cannot
flow freely but must be carried by ions.
Ions are formed when a solid such as salt is
dissolved in a liquid to form electrical
components having opposite electrical
charges (eg. Sodium chloride (NaCl)
separates to form Na+ and Cl- ions). All
ions present in a solution contribute to the
current flowing through the sensor and
therefore contribute to the conductivity
measurement.
The physical structure of a conductivity
sensor is important as in a liquid, the only
restrictions on an ion’s movement are the
physical limits of the liquid itself. A
conductivity analyzer measures all the
current that will flow between two charged
electrodes.
A conductivity sensor is
constructed so that there is an exact
volume between the two electrodes.
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Kcell = cell constant in 1/cm
R = measured resistance in ohms
kTC = temperature compensation factor as %
change per degree Celsius
TTC = measured temperature in degree Celsius
* Kcell can typically range from 0.01/cm to 50/cm.
resistivity =
1
conductivity
resistance =
1
conductance
cell constant = Kcell = l
A
l = length, in meters, of an electrical conductor
A = effective cross-sectional area, in square
meters, of an electrical conductor
1 µS/cm = 1 mho
1 mho = 1
ohm
Conductivity measurement is read out as:
microsiemens/cm (µS/cm)
OR
millisiemens/cm (mS/cm)
Measurement
Units
resistance
ohm
conductance
siemens, mho
resistivity
ohm·cm
conductivity
siemens/cm, ohm/cm
Table 1: Electrolytic measurement units
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CONDUCTIVITY MEASUREMENT
IC Controls
CONDUCTANCE DATA FOR COMMONLY USED CHEMICALS
Examples of conductance of various materials with changing concentration are shown below. Sodium Hydroxide (NaOH) also
exhibits quite variable temperature related rates of concentration change. It is clear from the graph that both Sulfuric Acid,
H2SO4, and Nitric Acid, HNO3, have unusual 'conductivity' vs. '% by weight' relationships as well. It clearly shows that there is
no “conductivity constant” between chemical combinations.
Illustration 1: Conductivity (µS/cm) vs Chemical concentration
Cell Constant
To determine the amount of current that
will flow through a known amount of
liquid, the volume between the two
electrodes must be exact and the current
must be kept consistent and moderate.
This is known as the cell constant. Any
effective volume change alters the cell
constant and current; too much volume
Page 4
will result in noise (low current) and too
little volume results in electrolytic effects
(high current).
The cell constant
recommended will vary depending on the
conductivity range of the solution. High
conductivity requires a high cell constant
and low conductivity requires a low cell
constant.
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CONDUCTIVITY MEASUREMENT
Industrial users may have a wide range of
applications with unpredictable variables.
Ideally, IC Controls would check the
ranges of conductance for all the
applications and recommend appropriate
cell constants. However, unknowns and
upsets in the process must be anticipated,
therefore, to accommodate these scenarios,
the IC Controls Model 455 conductivity
analyzer auto-range capability allows for a
ten-fold increase or decrease in range by
the microprocessor. The user can achieve
full accuracy at a far greater range than was
historically possible.
For example, a
1.0/cm cell constant recommended for 0
µS/cm to 1,000 µS/cm can read accurately
up to 0 µS/cm to 10,000 µS/cm or down to
0 µS/cm to 100 µS/cm full scale. Not only
is accuracy assured over a greater
conductivity range, but fewer cell constants
are required.
Temperature Compensation
Ionic
movement,
and
therefore
conductivity measurement, is directly
proportional to temperature (refer to
Illustration 2). The effect is predictable
and repeatable for most chemicals, but
Illustration 2: Temperature response of typical
solutions
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unique to each chemical. The effect is
instantaneous and quite large (typically 1%
to 3% / °C) with reference to the value at
25 °C (refer to Table 2 and Illustration 3).
Also, refer to the formula on page 3 where
kTC refers to percent change.
Substance
% change per °C
acids
1.0 to 1.6
bases
1.8 to 2.2
salts
2.2 to 3.0
neutral water
2.0
Table 2: Typical temperature responses
Industrial applications often demonstrate
temperature fluctuations and, as a result,
require temperature compensation. This is
generally accomplished by using an
automatic,
linear
temperature
compensation method. In most cases, the
variations in temperature are corrected
using
automatic
temperature
compensation; 2% per °C is deemed
acceptable.
Without
temperature
compensation, large errors can result, for
example: 50 °C x 2% / °C = 100% off the
true value, or 50% error in reading.
Illustration 3: Temperature compensation values
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CONDUCTIVITY MEASUREMENT
In
laboratory
applications
where
measurements must be made with accuracy
and consistency in various chemical
combinations,
manual
temperature
compensation can be considered for each
application. The temperature is set in the
manual TC mode.
For on-line process applications, the IC
Controls 455 conductivity analyzer allows
the user to set the TC constant in % per °C
to match the curve in the known
temperature range of the known process
chemical. Where the process mixture
produces an unknown, the default 2% / °C
can be used, or tests can be performed and
a custom value can be set in the 455.
Some chemicals that are frequently diluted
for use have changing non-linear
temperature compensation requirements so
IC Controls has programmed special
versions reflecting various TC curves in
the memory; eg. NaOH 455-21, H2SO4
455-22, HCl 455-23, NaCl 455-24; that
read out in percent concentration, plus
TDS (Total Dissolved Solids) 455-25,
resistivity 455-26, ppt salinity 455-27, and
very low conductivity water 455-28.
Sensor Cleaning
As mentioned earlier, the volume
(distance) between electrodes is exact. If
fouling of the sensor takes place, it can
actually alter the distance between
electrodes and change the cell constant as a
result. Therefore, keeping the electrode
clean is very important. The 455 analyzer
will determine the cell constant at the point
of calibration as well as condition of use
and compensate accordingly. Changing
cell constants will then not be a factor
adversely affecting repeatability.
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IC Controls
Calibration
Calibration is critical to accurate
measurement thus a calibration schedule
should be adhered to. While it is a quick,
single point process, it is important that all
applications be accurately reflected with
acknowledgment of the set TC and cell
constant. The 455 will keep in memory a
record of calibration dates, values, and cell
constants that can be downloaded to your
computer for proof of performance or to
trend the sensor cell condition. If the user
decides to calibrate using a laboratory
bench top unit as a calibration standard,
there is a grab sample method incorporated
into the 455 analyzer that enables the user
to standardize the reading to correspond
with the lab unit.
Using lab
standardization or using the high integrity
of the IC Model 455 calibration is the
convenient choice of the user.
Conductivity Calibration
Theory
Periodic calibration of conductivity sensors
in continuous use is recommended.
Various factors can affect the physical
limits on the liquid and the apparent cell
constant; scaling, biological growth, oils,
waxes, gum, etc. All reduce the area for
current-carrying liquid.
A conductivity cell's physical size and
shape are important. In a liquid, the only
restriction on an ion's movement are the
physical limits of the liquid.
A
conductivity analyzer measures all the
current that will flow between two
electrodes; if there are no restrictions, not
only will the shortest path between the
electrodes carry current, but also other
roundabout paths will carry a smaller share
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CONDUCTIVITY MEASUREMENT
of current. The controlled volume of a
good conductivity sensor places physical
limits on the liquid and controls current
paths, plus it is identified by the cell
constant.
The cell constant can be
accurately determined by dipping the
sensor cell area in a recognized
conductivity standard (preferably traceable
to NIST since literature references are
frequently in conflict over conductivity
values). The standard should be near the
high end of the operating range of the
sensor cell constant or the range of interest.
Low constants such as 0.01/cm tend to
have large electrode surfaces which are
close together, making for fairly large
sensors. They need a long, slim container
to be fully immersed in liquid for
calibration. Medium constants like 0.1/cm
and 1.0/cm are much smaller and more
compact and can usually be calibrated in a
beaker if kept suspended above the bottom.
High range cells with 10/cm, 20/cm or
50/cm constants usually include an internal
liquid passage that requires a long thin
vessel to be immersed or may require a
pumped sample for calibration.
NIST Traceable Standards
IC Controls manufactures conductivity
standards and QC's them using NIST
materials. Certificates of traceability to
NIST materials are available as P/N
A1900333.
Where To
Calibrations
Perform
Conductivity
A suitable place to conduct a calibration is
at a counter or bench with a sink in an
instrument shop or laboratory. However,
IC Controls provides kits that are kept
small and portable so that they can be
taken to installation sites together with a
bucket of water (for cleaning and rinsing)
and a rag/towel (for wiping or drying).
Calibration at the site offers the advantage
of taking into account the wiring to and
from the analyzer to sensor, and correcting
for any errors induced.
When calibrating, ensure that there are no
air bubbles inside the cell; they will cause
low conductivity readings.
Remove
entrapped bubbles by gently tapping
against beaker wall or alternate raising and
lowering the sensor in the beaker to flush
them out.
With the conductivity cell centered and no
air bubbles in the cell, allow the reading to
stabilize and then calibrate the analyzer.
Illustration 3: Conductivity calibration
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NOTE:
The reading may gradually
change for some time while the sensor
equilibrates to the standard temperature.
With analog conductivity analyzers the
technician must decide when the
temperature is stable and then turn the
standardize
adjuster.
With
microprocessors, the program acts as an
expert thermal equilibrium detector and
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CONDUCTIVITY MEASUREMENT
IC Controls
flashes its reading until the temperature
stabilizes.
A somewhat different but
steady (non-flashing) reading indicates
calibration is complete.
Selecting Conductivity
Sensors
In order to ensure integrity of conductivity
readings, several steps are needed to take
all of the above factors into consideration.
First, a survey should be made of all
applications; to the best of their ability, the
user should complete a
Conductivity
Application Analysis sheet for each
measurement point, factoring in varying
chemical
combinations,
conductivity
ranges and temperatures. This will allow
for a selection of sensor styles and cell
constants to allow standardization.
At this time, IC Controls would address the
following:
1)Sensor Recommendation – attempt to
stay with as few cell constants as possible
(ie. the IC Controls Model 404-1.0 may be
a suitable, economical choice).
2)Analyzer Recommendation – The IC
Controls Model 455 may be recommended
because of its wide range capability,
accuracy and automatic compensation
flexibility.
3)Cleaning Schedule – At least for fouling
applications, to sensor and cell constant
integrity. ensure
4)Calibration Schedule – To document
accuracy and ensure repeatability is
maintained.
ELECTRODE MODELS AND CELL CONSTANTS
Model / Cell Constant
0.01
0.02
401
Hot Condensate Sensor
0.1
0.2
X
X
0.5
1.0
2.0
X
X
402
High Purity Sensor
X
X
X
X
403
Ball Valve Sensor
X
X
X
X
X
X
X
X
X
X
X
X
404
General Purpose
405
Easy-Clean Sensor
X
X
406
High Conductivity Flow
414
True Union Sensor
425
Quick Union Sensor
5.0
X
X
20
X
X
50
X
X
X
10
X
X
X
X
Table 3: Electrode models and cell constants
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um-600SR2
IC Controls
CONDUCTIVITY MEASUREMENT
GUIDE TO CELL CONSTANT USABLE RANGES
CELL CONSTANT
DESIGN RANGE
LOWEST RANGE
HIGH RANGE
OVER RANGE *
0.01/cm
0 µS/cm to 10 µS/cm
0 µS/cm to 1 µS/cm
0 µS/cm to 100 µS/cm
0 µS/cm to 1,000 µS/cm *
0.02/cm
0 µS/cm to 20 µS/cm
0 µS/cm to 2 µS/cm
0 µS/cm to 200 µS/cm
0 µS/cm to 2,000µS/cm *
0.1/cm
0 µS/cm to 100 µS/cm
0 µS/cm to 10 µS/cm
0 µS/cm to 1,000 µS/cm
0 µS/cm to 10,000/cm µS *
0.2/cm
0 µS/cm to 200 µS/cm
0 µS/cm to 20 µS/cm
0 µS/cm to 2,000 µS/cm
0 µS/cm to 20,000µS/cm *
0.5/cm
0 µS/cm to 500 µS/cm
0 µS/cm to 50 µS/cm
0 µS/cm to 5,000 µS/cm
0 µS/cm to 50,000 µS/cm *
1.0/cm
0 µS/cm to 1,000 µS/cm
0 µS/cm to 100 µS/cm
0 µS/cm to 10,000 µS/cm
0 µS/cm to 100,000 µS/cm *
2.0/cm
0 µS/cm to 2,000 µS/cm
0 µS/cm to 200 µS/cm
0 µS/cm to 20,000 µS/cm
0 µS/cm to 200,000 µS/cm *
5.0/cm
0 µS/cm to 5,000 µS/cm
0 µS/cm to 500 µS/cm
0 µS/cm to 50,000 µS/cm
0 µS/cm to 500,000 µS/cm *
10.0/cm
0 µS/cm to 10,000 µS/cm
0 µS/cm to 1,000 µS/cm
0 µS/cm to 100,000 µS/cm
0 µS/cm to 1,000,000 µS/cm *
20.0/cm
0 µS/cm to 20,000 µS/cm
0 µS/cm to 2,000 µS/cm
0 µS/cm to 200,000 µS/cm
0 µS/cm to 1,000,000 µS/cm *
50.0/cm
0 µS/cm to 50,000 µS/cm
0 µS/cm to 5,000 µS/cm
0 µS/cm to 500,000 µS/cm
0 µS/cm to 1,000,000 µS/cm *
* NOTE: Use with caution, some sensor designs may limit when used on over-range, and may not reach the maximum shown.
Table 4: Guide to cell constant usable ranges
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Page 9
INSTALLATION
IC Controls
INSTALLATION
Selecting the Location
The sensor should be positioned to monitor
the change of interest (eg. after the leak
point) for optimal response. Long sample
lines should be avoided wherever the
conductivity signal must be responsive to
sudden changes in order to avoid sample
transport lag problems. For the sensor to
work correctly, the installation location
must ensure that the cell is always
completely full of liquid. Care must be
taken to ensure any bubbles entrained in
the liquid will not lodge in the cell cavity
as the void they create in the measuring
circuit will reduce the current flow and
produce an erroneous result. Similarly,
solids or sludge that may coat the
electrodes should be taken into account
and the sensor positioned to pick up the
cleanest possible sample.
The most
satisfying installations also provide for
easy sensor calibration with sensor
removal room and at least 1 m of flexconduit for calibration.
replacement, and the electrical conduit. IC
Controls recommends 10 cm (4 in)
minimum
separation
between
rows/columns.
Pipe mounting kits for 5 cm (2 in) pipe, are
also available. This kit may also be used to
surface mount the transmitter by removing
the 2 inch U bolts and using the holes in
the mounting plate for wall studs (using
customer-supplied studs).
Panel mounting kits are also available.
This kit requires a customer supplied panel
cut-out.
Sensor Mounting
It is recommended that the sensor be
located as close to the conductivity
transmitter as possible in order to minimize
any effects of ambient electrical noise
interference. Flow sensors can be in any
orientation but should be mounted tip
down at an angle anywhere from 15
degrees above horizontal to vertical; 15
degrees above horizontal is best because
air bubbles will rise to the top and debris
will sink, both bypassing the sensor.
Analyzer Location
M ax 90
The sensor is typically supplied with 3 m
(10 ft) lead as standard. Ideally, the
analyzer should be kept within the sensor
lead length and mounted on a wall at eye
level. Position the analyzer so that with
the sensor still connected, the sensor may
be removed and the electrode tip placed in
a beaker on the floor for cleaning or
calibration. Assume the safest place for
the beaker is on the floor the service
person stands on. Horizontal separation
between rows of analyzers should allow for
electrode leads which need periodic
Page 10
M in 1 5
Illustration 4: Sensor mounting
Submersion sensors should not be mounted
where a lot of air bubbles rise in the tank;
air bubbles will cause spikes in the
conductivity readout.
If a bubble is
allowed to lodge in the sensing tip,
electrical continuity between the electrodes
may be disrupted.
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INSTALLATION
Typical Flow Mounting
Flow type installations available are:
1. 316 SS flow cell for use on hot
condensates
and
pure
water
applications; option -73 for model 401
and 402 sensors, P/N A3100071.
2. CPVC flow cell, 1 inch FNPT for use
with model 405 sensor; option -73, P/N
A3100146.
3. Flow cell with 1½ inch FNPT
connections; for use with model 425
sensor:
CPVC, option -73, P/N A2300073.
316 SS, option -75, P/N A2300075.
4. Flow cell with 1 inch FNPT
connections; for use with model 414
sensor:
CPVC, option -24, P/N A2300124.
316 SS, option -23, P/N A2300123.
PVDF, option -22, P/N A2300122.
5. CPVC 1½ inch flow cell, 1 inch
connections; for use with model 406
sensor, option -75, P/N A2100051.
Install the housing vertically and position
the sensor so that the cross channel or vent
hole is below the cell outlet. This will
ensure the cell is full at all times, even if
the exit pipe drains to atmosphere and air
can enter. Flow should be upwards and out
the side thereby flushing any air bubbles
out of the cell area.
An alternative installation is possible with
the flow housing at 45 degrees and the side
vented; bubbles should be released but
debris will cause a problem if present.
Never install in such a way that the internal
cell area of the sensor is inverted; it will
accumulate any solids and short the sensor
or give erroneous readings.
The housings can be used as an in-line
body or in a side stream line. Always
place on the pressurized side of a pump,
not the suction side, and if using as an inline arrangement, allow for the added flow
resistance caused by the sensor body.
Typical Insertion Mounting
Insertion type installations available are:
1. 316 SS insertion gland fitting, ¾ inch
MNPT, for use with model 403 sensor;
option -74, P/N A3100002.
2. Direct threaded for insertion with model
401, 404 and 405 sensors.
3. Quick connect insertion fitting with 1
inch MNPT connections; for use with
model 414 sensor:
CPVC, option -26, P/N A2300126;
60 psi at 90° C (194° F).
316 SS, option -28, P/N A2300128;
100 psi at 150° C (302° F).
PVDF, option -29, P/N A2300129;
100 psi at 110° C (230° F).
4. Quick connect insertion fitting with 1½
inch MNPT connections; for use with
model 425 sensor:
CPVC, option -76, P/N A2300086;
60 psi at 90° C (194° F).
5. Ball Valve Insertion Retractable; model
403 sensor.
Illustration 5: Recommended piping
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INSTALLATION
IC Controls
If the vessel will be full at all times when
the conductivity needs to be measured, the
sensors can be inserted into a threaded
opening. The location must ensure the
sensor is fully submerged and not subject
to blanketing with deposits.
The major consideration for insertion
mounting is that a hole exists in the
vessel/pipe wall when the sensor is
removed for calibration, etc. The IC
Controls model 403 ball valve retractable
sensor was developed to address this
problem. With its use, the benefits and
economy of no sampling system are
available even where the process must stay
pressurized or draining the system would
be costly.
Removal clearance is necessary with any
insertion sensor; usually 12 inches is
sufficient. With the 403 retractable sensor,
a 30 inch clearance is required as the
sensor typically extends about 18 inches
from the mounting opening.
Typical Submersion Mounting
Circulation is the prime consideration in
installing a submerged sensor.
The
location must have sufficient flow or
agitation to ensure a representative sample
reaches the sensor. Sensors with surface
electrodes are preferred for this service;
never use model 403 or 406 sensors as they
have long internal passages that would not
see adequate circulation without a forced
flow.
For dirty applications such as sewers, the
405-2.0 sensor with flat surface presents an
easy to clean solution; however, care must
be used to ensure it is not placed closer
than 2 inches from the channel bottom.
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Submersion can be up to 3 m (10 ft) or
more with most IC Controls sensors
(standard lead length is 3 m). To assure a
fixed position, the sensor should be
mounted in a female thread on the end of a
1¼ inch Sch. 80 PVC or SS pipe. Smaller
diameter pipe can be used with a coupling
to adapt where whipping due to flow
resistance will not present a problem. IC
Controls recommends mounting a 40078xp J-box on top of the pipe, cutting the
sensor leads to approximately 12 inches
longer than needed to reach the junction
box and terminating there. For ease of
calibration, allow for pipe length plus 1 m
to 1.5 m extra flex-conduit, and where
possible, install the support pipe on a
channel iron quick disconnect rail.
Sensor Wiring
The basic wiring scheme for all IC
Controls conductivity sensors is shown in
drawing D5920095, plus a description of
the 400 interface to the analyzer. This
wiring scheme is intended for cable runs
less than 20 m (65 ft) where electrical
interference is low. This cable is available
from IC Controls as P/N A9200000. Use
of other cables is not recommended since
experience has shown that many other
cables have a capacity that interferes with
the conductivity sensor signal resulting in
errors.
Take care to route all sensor wiring away
from AC power lines to minimize
unwanted electrical interference. When
installing sensor cable in conduit, use
caution to avoid scraping or cutting the
cable insulation; the resulting short of the
cable's internal driven shield will cause
conductivity errors. Avoid twisting the
sensor lead to minimize possibilities for
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INSTALLATION
broken wire and make sure the sensor
connections are clean and tight.
Connections
IC Controls' conductivity sensors are
supplied with four leads. Black and white
leads are always connected to the sensor
cell electrodes. They should be insulated
from each other and from the temperature
compensator (TC) between them with
insulation to ground or the cell leads. TC
leads are not polarity specific, however,
with some concentric electrode sensors,
use of white as probe drive and black as
probe sense is required.
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INSTRUMENT SHOP TESTS
IC Controls
Testing With The Analyzer
INSTRUMENT SHOP
TESTS
Refer to your analyzer's instruction manual
for proper wiring instructions unique to it.
Checking The Sensor
1. Apply power to the analyzer.
The sensor should be checked against the
ordered specification to ensure the correct
sensor is being used for the specified
application. Refer to specification sheets
and sensor selection guide to confirm the
model number received. Electrical checks
may be made to ensure the sensor is in
good condition before installation.
Between the white and black cell leads, the
insulation value should exceed 1 MΩ.
Between the yellow and green TC leads,
there should appear the resistance value
given for the TC at 25 °C ± 10%. Between
either TC lead and either cell lead, the
insulation values should exceed 1 MΩ.
2. Hook up the sensor and remove the
orange protective cap (for this example
assume a 2.0/cm cell constant).
Preparation For Use
6. To check for general performance, place
the sensor in 100 μS/cm standard. The
display should read close to 100 μS/cm.
1. Moisten the sensor body with tap water
and remove the protective storage cap at
the sensor tip. Rinse the exposed
conductivity elements with tap water.
2. For first time use, or after long term
storage, immerse the lower end of the
sensor in a conductivity standard for 30
minutes; this wets the conductivity
electrodes and prepares them for stable
readings with test solutions.
3. With the sensor in air, the conductivity
analyzer should come up reading 0.0
µS/cm ± 0.5 µS/cm.
4. Perform an “air” zero calibration; use
wires to be field installed and allow 30
minutes warm-up time for the
electronics to stabilize.
5. Perform a “Std.” (span) calibration by
placing the sensor in 1000 μS/cm
standard.
The display should read
approximately 1000 μS/cm ± 10 μS/cm.
7. The sensor is now ready for field
installation.
8. It is suggested that your analyzer be set
up at this time. Refer to your analyzer
instructions.
NOTE: IC Controls' sensors are shipped
dry. These electrodes are often ready for
use immediately with a typical accuracy of
± 2% conductivity without calibration.
However, it is recommended to soak the
sensor in standard and proceed to calibrate
with an appropriate conductivity standard
to achieve optimal performance.
Page 14
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IC Controls
CONDUCTIVITY CALIBRATION
CONDUCTIVITY
CALIBRATION
The conductivity sensor-analyzer system is
usually
calibrated
using
standard
conductivity solutions.
Alternatively,
grab-sample analysis on a previously
calibrated
laboratory
reference
conductivity meter can be used.
Ionic
movement,
and
therefore
conductivity,
is
proportional
to
temperature. The effect is predictable and
repeatable for most chemicals, although
unique to each. It is instantaneous and
large, typically 1% to 3% per degree
Celsius.
Overall system accuracy is maintained by
calibrating the sensor and analyzer together
in a standard close to the expected sample
concentration. Calibration determines the
effective cell constant of the conductivity
sensor. The cell constant is affected by the
shape of the sensing surface and electrode
surface characteristics. The effective cell
constant will change over time as deposits
form or as a result of anything else
affecting either the controlled volume or
the effective electrode surface area.
10,000 μS/cm conductivity standards are
calculated by the analyzer. Simply place
the sensor in the selected standard and the
455 analyzer will use the correct
temperature adjusted value for that
standard.
Temperature Dependence of
Standards
The formula for the temperature-corrected
conductivity value C25 is:
C25 =
CT
1 + α(T – 25)
where;
CT
T
α
= conductivity at the current temperature
= current temperature
= temperature compensation constant
The temperature compensation constant for
IC Controls' standards is 2% per °C.
If manual temperature compensation has
been selected, then the manual temperature
compensation set point is used as the
standard's temperature.
Measure the
standard temperature and enter it for best
accuracy.
Selecting a Standard
Other Standards or Custom
Standards
Conductivity standards provide the
simplest and most accurate method of
calibrating the conductivity sensor and
analyzer. Some analyzers, such as IC
Controls' 455, have been programmed to
correct for the three most common
standards used for calibration:
100
μS/cm, 1,000 μS/cm, and 10,000 μS/cm at
25 °C (77 °F).
To achieve greater
accuracy, the temperature compensated
values for the 100 μS/cm, 1,000 μS/cm and
If a “custom value” conductivity standard
is to be used, the custom value will need to
be entered in the calibration menu. Refer
to the analyzer instruction manual. Using
IC Controls' 455 analyzer, press SELECT
and using the up/down arrow key display
[Cal].
Press SELECT and using the
up/down arrow key display [100]. Press
ENTER and edit the blinking value to the
known value and press ENTER. Values
entered this way should be the known
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Page 15
CONDUCTIVITY CALIBRATION
value at the current temperature; they are
not temperature-compensated by the
analyzer.
Where to do Conductivity
Calibrations
A suitable place to conduct a calibration is
at a counter or bench with a sink, in an
instrument shop or laboratory. However,
IC Controls' conductivity calibration kits
are kept small and portable so that they can
be taken to installation sites, together with
a bucket of water (for cleaning/rinsing) and
a rag/towel (for wiping or drying).
Calibration Using Standards
Select a conductivity standard with a
concentration that is close to and above the
expected sample concentration. A second
conductivity standard can be used to verify
that the conductivity sensor is responding
properly. This second standard can be any
value, but typically 10% of the first
standard works well giving checks at 100%
and 10% of range.
1. Obtain calibration supplies such as a
graduated cylinder or beaker which is
large enough to submerse the
conductivity sensor, plus distilled or demineralized water in a squeeze bottle
for rinsing, or an IC Controls calibration
kit.
2. Remove the conductivity sensor from
the process and inspect the sensor for
any deposits. If the sensing surface is
coated, clean the sensor before
proceeding.
Refer
to
Sensor
Maintenance, Chemical Cleaning.
Rinse the sensor cell area with distilled
water.
Page 16
IC Controls
3. Rinse the graduated cylinder or beaker
with some of the standard, then pour the
selected higher conductivity standard
into the graduated cylinder or beaker.
4. Immerse the sensor and ensure the
sensor electrode area is completely
submerged. If the sensor has vent holes
then the sensor must be submerged
below the vent holes and there must be
no air bubbles inside.
IMPORTANT:
a) Air bubbles inside the controlled
volume area of the conductivity sensor
cause major upsets to ion flow and
result in large errors in the reading.
b) If the analyzer is not reading on scale,
it may be because the range is
incorrect. Select a different range
until a reading comes up.
5. From the menu, select the standard
value of the standard being used.
6. Proceed with calibration. Wait until the
reading has stabilized, then adjust the
reading to the temperature-compensated
value of the conductivity standard.
NOTE:
a) Digital analyzers may perform this
step automatically.
b) Repeat the process to ensure the
calibration is correct.
7. The conductivity sensor and analyzer
pair are now calibrated.
Used conductivity standard should be
discarded because exposure to air and
contamination causes the conductivity of
standards to change.
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IC Controls
CONDUCTIVITY CALIBRATION
NOTE:
The sensor condition can be verified by
measuring the concentration of a second
standard.
Rinse the sensor surface with demineralized water and then measure the
concentration of the second standard
(refer to step 4). If the analyzer reads
correctly then the sensor condition is
good. If the analyzer does not read
correctly then the sensor may not be
responding properly and may need to be
cleaned.
Grab-Sample Calibration
The grab-sample technique is quicker and
easier if the sensor is not easily accessible.
This procedure describes how to calibrate
the analyzer without taking the sensor out
of the process. The procedure requires that
the sample be measured with a second
analyzer. Typically, a laboratory analyzer
is used to determine the actual conductivity
of the sample.
1. Obtain the following materials:
a
second conductivity analyzer, a sensor
of known cell constant, calibration
standards, a clean beaker for taking a
sample, and a calculator.
2. Record the cell constant of the sensor if
available. The cell constant is typically
displayed by pressing SAMPLE and
then selecting [cond] [CELL] [1] from
the menu.
3. Draw a sample from the process. In
order for the procedure to work
properly, ensure that the sample drawn
is representative of the sample being
measured by the conductivity analyzer.
um-400SR2
4. Record
the
conductivity
and
temperature of the sample as displayed
by the conductivity analyzer.
5. Measure the conductivity of the sample
using the second conductivity analyzer
and record the conductivity reading.
For accurate results, the sample must be
at the same temperature and the
analyzer must use the same temperature
compensation method.
6. For IC Controls' digital analyzers,
calculate the new cell constant to be
entered into the analyzer using the
following formula:
new cell
= lab reading × old cell
field reading
For example, if the analyzer was
reading 820 μS/cm, the cell constant
(from step 2) was 1.0 μS/cm, and the
reading from the second analyzer was
890 μS/cm; the new cell constant
becomes :
new cell = 890 × 1.0 = 1.09 μS/cm
820
7. For IC Controls' digital analyzers, adjust
the cell constant to the new value; 1.09
μS/cm as in the above example.
8. For older analyzers with standardize
adjustments, return to the unit and note
the current reading (eg. 840 μS/cm).
Adjust the current reading to 1.09 times
it's value;
840 μS/cm x 1.09 μS/cm = 916 μS/cm
9. The analyzer
accurately.
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should
now
read
Page 17
SENSOR MAINTENANCE
IC Controls
SENSOR MAINTENANCE
Sensor Removal Warning!
Before sensor removal, the process
pressure at the sensor must be lowered to
zero, or a dangerous pressure stream of
process liquid will blast out. Models 401,
402, 405, 406, 414 and 425 sensors may
leave a hole in the line, vessel or tank
when removed, and are intended for use
only where pressure can be lowered to
zero for servicing. Use of model 403 ball
valve insertion/retractable sensor is
recommended where pressure cannot be
reduced to zero for service.
Vessels and tanks must be drained until the
liquid level is below the sensor insertion
hole for the pressure to be zero and no
process liquid to escape.
Submersion installations can typically be
lifted out with the concern being liquid on
the support pipe or wires.
Use rubber gloves and appropriate face/eye
protection when handling sensors coated
with aggressive liquids.
Sensor Insertion
Sensors should be examined for good clean
sealing surfaces and be reinstalled
carefully. Clean seals such as O-rings
should be lubricated with silicone grease to
ensure liquid tight performance.
Removal of 403 Ball Valve
Sensor
1. Inspect the safety cables and replace if
corroded or damaged; P/N A1100011.
Page 18
Caution! With hot processes, there is
a risk of steam jets or liquid squirts.
The gland has two seals to reduce this
risk but scratches and grit may defeat
them.
2. Release the gland nut slowly, about 2 or
3 turns, allowing the sensor to slide
back until the safety cables are tight.
3. Once the 403 is fully retracted and
cables are tight, close the ball valve.
4. Remove the gland nut completely.
5. Remove the safety cables from the valve
housing.
6. The 403 body can now be removed.
NOTE: Always inspect and clean the 403
sensor body, gland, and seals, plus, relubricate the seals before reinstalling.
Sensor Storage
Short Term: Rinse the sensor electrodes
in demin water, allow to dry and store dry.
Long Term: Rinse the sensor electrodes
in demin water, allow to dry and cover
sensor tip with a plastic shipping cap and
store dry.
Monthly Maintenance
A monthly maintenance check is
recommended by grab sample calibration
since the sensor is typically installed in the
process and not easy to remove. Follow
the procedure for Calibration by Grab
Sample. Keep a log of the cell constant at
each monthly calibration.
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um-600SR2
IC Controls
SENSOR MAINTENANCE
Yearly Maintenance
Follow
the
monthly
maintenance
procedure. Check the cell constant log. If
the cell constant has changed more than
20% over the past year, it may need to be
chemically cleaned; follow the Chemical
Cleaning of Sensor procedure.
O-rings and teflon-sealing ferrules should
be replaced on models 402, 403, 414, and
425 sensors. The condition of electrical
connections in 400 junction boxes should
be examined for signs of corrosion and
tight connections. Replace if corroded.
The condition of the safety cables on 403
sensors should be examined for rust or
bent mounting screws. Replace if signs of
deterioration are evident.
scratch the electrode surfaces. Internal
cavities of standard sensors can be brushed
with a soft ¼ inch diameter brush.
The wetted surfaces of plastic body sensors
should be washed thoroughly with a soft
cloth. This will restore their appearance to
like-new condition and remove areas
where potential buildups are likely to
occur.
When to Chemical Clean
After cleaning as per above, check the
sensor against a conductivity standard. If
the sensor is still not developing the proper
cell constant ±5% (or reading near the
standard value) proceed to the chemical
cleaning procedure; otherwise return the
sensor to the process.
When To Clean The Sensor
Troubleshooting Hints
Various factors can affect the physical
limits on the liquid and the apparent cell
constant; scale, biological growths, oils,
wax, gum, etc., all reduce the area for
current-carrying liquid. Periodic cleaning
of conductivity sensors in continuous use
will remove these deposits, restore the
conducting surfaces and controlled cell
volume, and, as a result, the cell constant.
Slow response - typically due to excessive
sample line length and low flow, thus
producing long sample transport lags.
Resolve by adding a fast flow loop with the
sensor in a short side stream or by
shortening the line.
Slow response can also be caused by a
buildup of dirt in the sample line. In this
case, the problem may be alleviated by
changing the take off point or by installing
a knock-out pot.
Mechanical Cleaning of Sensor
The sensor will require cleaning if sludge,
slime, or other tenacious deposits build up
in the internal cavities of the sensor.
Wherever possible, clean with a soft brush
and detergent. General debris, oil films
and non-tenacious deposits can be removed
in this way.
For flat-surface sensors, use a potato brush
and a beaker or bucket of water with a
good liquid detergent. Take care not to
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Readings consistently low or spike lowcharacteristic of air bubbles in the sample
line passing through the sensor or hanging
up in the sensor.
Readings gradually falling - the analyzer
can no longer be calibrated properly. This
problem is typical of scale or sludge/slime
deposits in the sensor. The sensor may
need to be cleaned.
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Page 19
SENSOR MAINTENANCE
IC Controls
Readings at maximum - under all
conditions. First, verify that analyzer is
displaying conductivity using μS/cm units.
Some analyzers will display "+Err" if
conductivity is above 9,999 μS/cm with
µS/cm units selected for the display.
If unit selection is not the problem, then
either the sensor is shorted or there is a
problem with the wiring/analyzer setup.
Test for shorts by disconnecting wiring and
checking impedance between black and
white lead with sensor in air.
The
insulation value should exceed 1 MΏ . If
the sensor is OK then substitute resistors
for the sensor to test the wiring and the
analyzer. If the problem persists with the
resistors in place then it is an analyzer
problem. Use the following formula or
consult the table below for resistance
values to use.
Resistance (Ω) = Cell Constant х 106
µS of solution at 25 °C
Conductance Resistance (Ω); Resistance (Ω);
(µS/cm)
1.0/cm cell
0.1/cm cell
constant
constant
1
1 000 000
100 000
10
100 000
10 000
100
10 000
1 000
1 000
1 000
100
10 000
100
10
100 000
10
1
1 000 000
1
0.1
If the sensor tests OK (eg. no shorts) and
the analyzer and wiring work OK with
substitute resistors as in Table 5, but the
"+Err" or over scale still occur when the
analyzer and sensor are hooked up and
placed in service, then the conductivity is
likely too high for the cell constant used.
Resolve by determining the actual
conductivity and selecting a new
conductivity sensor with the correct cell
constant.
Elevated readings on low conductivity the analyzer reads high at the low end of
the range. In some cases the analyzer will
give a low reading even with the
conductivity sensor in air. Large zero
signals are indicative of a wiring problem.
Look first at shielding between leads and
ensure the shield is connected to the
analyzer shield terminal rather than
electrical ground. Other known causes
include incorrect cable or a cable length
too long for the application.
Where the elevated zero is small, it is
likely due to cable resistance/capacitance
and can be zeroed out using the air zero
calibration procedure.
The above symptoms cover most
difficulties associated with conductivity
sensors.
The major key to isolating
problems to the sensor or analyzer lies in
being able to separate the two with resistor
simulation.
For difficult problems,
assistance is available from IC Controls;
call toll free at 1-800-265-9161.
Table 5: Resistance values for simulation
Page 20
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IC Controls
SENSOR MAINTENANCE
Chemical Cleaning of Sensor
A1400054 Instruction Sheet
The A1400054 is a Conductivity Sensor
Chemical Cleaning Kit of solutions and
necessary items.
It contains the following:
Cleaning: 4 x 500 mL Clean & condition solution
Rinse:
1 x 500 mL Demin water
Beakers: 2 x 250 mL plastic
Syringe:
1 x 10 mL
Gloves:
1 pair rubber gloves
Brush:
1 sensor cleaning
Instructions for A1400054 Conductivity
Chemical Cleaning Kit
NOTE 1: A suitable place to perform
chemical cleaning is at a counter or bench
with a laboratory sink, and a chemical
drain where waste is contained and treated
before release.
NOTE 2: IC Controls kits are kept small
and portable so that they can be taken to
installation sites, together with a plastic
bucket of water (for rinsing) and a
rag/towel (for wiping or drying). Waste
materials (particularly acid leftovers)
should be returned to the laboratory sink
for disposal.
Caution! use extra caution when handling
cleaning solution as it contains acid.
Wear rubber gloves and adequate facial
protection when handling acid. Follow all
A1100005 MSDS safety procedures.
a) Set up the cleaning supplies where
cleaning. is to be performed Lay out the
sensor cleaning brush, syringe, cleaning
solutions and rinse solutions, plus the
beakers and sensor if already at hand.
um-400SR2
NOTE: Ensure the cleaning solution
beaker is on a firm flat surface since it
will contain acid.
b) First, remove the conductivity sensor
from the process and examine it for
deposits. Use the sensor cleaning brush
and tap water to loosen and flush away
any
deposits
within
the
cell
measurement area. Detergent can be
added to remove oil films and nontenacious deposits. Hard scale and
other tenacious deposits may require
chemical cleaning.
c) CHEMICAL CLEANING.
Fill a
beaker ¾ full of cleaning and
conditioning solution, P/N A1100005;
for flow-through sensors, seal one end
to form a container inside the sensor
body.
d) Lower the conductivity cell into the
center of the beaker until the top hole is
submerged; for flow-through sensors,
pour the solution into sensor body until
the sensor is full.
e) Keep removing and re-immersing the
sensor until the sensor electrodes appear
clean.
Stubborn deposits can be
removed with the brush and syringed on
hard to reach areas.
Caution!
Use great care when
brushing and squirting acid. Wear
rubber gloves and facial protection.
f) Rinse the cleaned sensor thoroughly in
tap water. Then rinse again with demin
water before calibrating.
g) Check the sensor against a conductivity
standard near full scale. If the sensor is
still not developing the proper cell
constant ± 5% (or reading near the
standard value), re-clean or proceed to
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Page 21
SENSOR MAINTENANCE
IC Controls
troubleshooting tips or replace sensor.
CONDUCTIVITY SENSORS
h) A clean, rinsed and dried conductivity
sensor should read near zero in air. If it
does not, troubleshoot the sensor,
wiring, and analyzer.
IC Controls sensors are available in the
following types:
1. submersion service
2. sample side stream service (flow
through)
Available Supplies:
3. insertion through pipe/tank wall
installation
A1100161
100 μS/cm,
-6P = 6 pack
A1100162
1,000 μS/cm,
- 6P = 6 pack
A1100163
10,000 μS/cm,
-6P = 6 pack
A1100164
100,000 μS/cm,
-6P = 6 pack
A1900333
Trace to NIST certificate
A1100192
Demin water,
A7400020
Poly beaker
A4700030
10mL syringe
A1100016
Sensor cleaning brush
A1400051
Low conductivity calibration kit
A1400052
Medium conductivity calibration kit
Sensor Models for Conductivity Service:
A1400053
High conductivity calibration kit
401
SS Hot Condensate Sensor 3
A1400054
Conductivity chemical cleaning kit
402
SS High Purity Water 2,3,6
403
SS Insertion/Ball Valve Retractable 4
404
General Purpose Sensor 1,7
405
Easy-clean Sensor 5,7
406
High Conductivity Flow Sensor 2
414
True-Union Conductivity Sensor 1,2,3,5
425
Quick-Union Universal, Industrial 1,2,3,5
-6P = 6 pack
4. insertion with ball valve for retraction
without lowering process pressure
5. universal type;
flow/submersion/insertion
6. pure water (low conductivity) service
7. dirty water (sewer, sludge, mine slurry,
pulp stock) service
Various other options may also be selected,
refer to the IC Controls catalog for full
details, or contact Customer Service at:
Toll Free:
(800)265-9161
Phone: (519)941-8161 ext. 116
Fax:
(519)941-8164
Email: sales@iccontrols.com
Web Site:
Page 22
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IC Controls
DRAWINGS
DRAWINGS
D5920095; Sensor Wiring
Title:From AutoCAD Drawing "R:\DWG\D50
Creator:AutoCAD
CreationDate:4/19/99 10:0:14
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Page 23
GLOSSARY
IC Controls
GLOSSARY
mho
The reciprocal of ohm; ohm spelled backwards. The equivalent of mho/cm is siemens
(S), which is the modern naming for this unit.
μS/cm
Unit of conductivity, μS is symbolic for microsiemens.
meaning one millionth.
Micro is the metric prefix
Cell constant
Describes enclosed volume between electrodes in the conductivity sensor; units are cm-1.
Higher cell constants produce higher analyzer ranges and lower cell constants produce
lower ranges.
Conductivity
The amount of electrical current that flows through a liquid. Generally reported as
μS/cm.
mS/cm
Unit of conductivity, mS is symbolic for millisiemens. Milli is the metric prefix meaning
one thousandth.
1 millisiemens; 1 mS/cm = 1000 microsiemens; 1000 μS/cm
siemens (S)
SI (Systeme Internationale, or the International System of Units) derived units for electric
conductance. Expression in terms of other SI units: A/V.
TC
Temperature compensator
Temperature Compensation
Correction for the influence of temperature on the sensing electrode. The analyzer reads
out concentration as if the process were at 25° C of 77° F, regardless of actual solution
temperature.
Page24
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um-600SR2
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