Conductivity Measurement in High Purity Water Samples below 10 µSIEMENS/cm - IC Controls
                      CONDUCTIVITY MEASUREMENT  IN  HIGH PURITY 
WATER  SAMPLES below 10  µSIEMENS/cm
High Purity Water Resistivity/ 
Conductivity Measurement
Ultra-Pure Water without any chemical 
impurities will still have a conductivity 
because of the presence of H+ and OH- ions 
due to the self-ionization of water. Ultra-pure 
water has a conductivity of 0.055 
µSiemens/cm or a resistivity of 18.18 mΩ·cm 
at 25 °C. In order to know the conductivity or 
resistivity of ultra-pure water it is required to 
do accurate temperature compensation at very 
low conductivities, e.g. conductivities below 
10 µSiemens/cm. An IC Controls 210-C 
analyzer in High Purity Water configuration 
(HPW) is intended for use with a 402 side 
stream sample sensor, or 403 direct 
insertion/retractable sensor, with a 0.01/cm 
cell constant. It will accurately measure the 
conductivity (or electrical conductivity) or Illustration 1 conductivity of pure water
resistivity (electrical resistivity) of pure water 
samples below 10 µS/cm in continuous 
flowing samples.  Since pure water conductivity measurement is 
The self-ionization of water is strongly detecting trace amounts of ionic contaminants 
temperature-dependent. For accurate in the already temperature dependent self-
temperature compensation the conductivity of ionizing water, the installation and calibration 
the pure solvent must be subtracted from that setup must make special provisions to 
of the solution to determine the conductivity eliminate or reduce any trace contaminants. 
of the electrolyte. Simply applying a linear Further, the trace contaminants themselves 
per-degree-Celsius temperature adjustment exhibit variable temperature coefficients in 
will not give accurate temperature pure water that can rise as high as 7 % per °C. 
compensation in high purity waters. Some such as NaOH for instance can cause 
conductivity at trace levels to go negative by 
Illustration 1 shows the conductivity of ultra-
µ suppressing the conductive H
+ions with the 
pure water in  Siemens/cm over the range 
less conductive OH-ions resulting in a reading 
0 °C to 100 °C. below that of theoretically pure water.  The 
IC Controls application Notes Issue 4.2 ©IC Controls 2012
IC Controls 210-C analyzer has different certified cell constant, traceable directly to 
temperature coefficient algorithms to allow the NIST Standard Reference Material 3191 of 
user to select for neutral salts, acidic, or basic 100 µS/cm. Alternatively IC Controls can 
samples (as well as the traditional linear % per factory-certify the sensor cell constant with 
°C). Standard “D” of ASTM method D1125, 
Since high-purity water contains little 146.93 µS/cm.
dissolved material it is like a dry sponge ready To meet ASTM D5391-99 sensor needs, use 
to soak up any contaminant it meets. an option -73 flowcell to exclude air contact 
Absorption of carbon dioxide on exposure to with the sample, followed by a sample take-off 
air will result in carbonic acid formation and point where an additional sensor can be 
cause a real change in conductivity of up to 2 installed for calibrations. When installed in a 
to 3 µS/cm. This fact can be readily shared sample line with pH sensors, the 
demonstrated by taking a beaker of fresh conductivity sensor should be first, because 
demin water from a laboratory column, with pH reference electrodes will leak KCl into the 
conductivity electrode inserted and showing sample, thereby raising its conductivity. The 
less than 0.5 µS/cm, then bubbling conductivity sensor should be located as near 
compressed air through it and observing the as possible to the conductivity transmitter, to 
conductivity reading quickly rise to between 2 minimize any effects of electrical noise 
and 3 µS/cm. Also if dissolved gases are in the interference. Flow sensors can be in any 
sample, on exposure to air they may escape orientation but should be mounted tip down at 
(similar to opening a bottle of pop). Similarly an angle anywhere from 15° above horizontal 
air exposure will allow CO2 and other soluble to vertical, 15° above horizontal is best 
gases to dissolve into the sample raising the because entrained bubbles will rise to the top 
conductivity. Clearly, calibrations using open and grit will sink.
containers of high purity water will have Stainless steel sample lines are recommended 
problems that the same samples in for pure water samples to maintain their 
continuously flowing enclosed tubing should integrity. The sensors can handle pressures up 
not encounter. to 100 psi. Any sample flow rate will work, 
however 2 meters per second (6 feet per 
Designed to meet ASTM D5391- second) has been found to minimize iron oxide 
99 and be Traceable to NIST grit buildups.
The IC Controls 210-C analyzer together with The low-level sensor signals should be run 
a model 402 or 403 sensor with cell constant through a dedicated conduit. Take care to route 
0.01/cm and -73 flow cell is designed to meet the signal wiring away from AC power lines, 
the requirements of ASTM D5391-99 for to minimize unwanted electrical interference. 
Flowing High Purity Water Samples (less than When installing sensor cable in conduit, use 
10 µS/cm), when calibrated with A1100161 caution to avoid scraping or cutting the cable 
NIST traceable 100 µS/cm standard or insulation, the resulting short of the cable’s 
A1100232 conductivity standard “D” internal driven shield will cause conductivity 
146.93 µS/cm. To obtain the full benefits, the errors. Avoid twisting the sensor lead, to 
user should acquire a copy of the standard and minimize possibilities for broken wire. Sensor 
ensure sampling and calibration techniques connections need to be clean and tight.
used on site meet the requirements of the 
standard. Pure Water Formula Selection
The IC Controls 402-0.01 conductivity sensor Much work has been done over the years to 
(or the 403) can be provided with factory- 
IC Controls application Notes Issue 4.2 ©IC Controls 2012
establish the temperature dependence of pure 
water. Early analog implementations used °C µS/cm MΩ·cm
thermistors to achieve temperature 0 0.01165 85.841
compensation, but may not have been very 
accurate. Current microprocessor technology, 5 0.01661 60.217
such as in the 210-C, allows for accurate, 10 0.02310 43.297
continuous compensation over the entire 15 0.03143 31.820
temperature range 0-100°C.
20 0.04194 23.844
The earliest widely-used pure water equation 
was developed at the General Electric 25 0.05501 18.180
Vallecitos Nuclear Training Center. This 30 0.07101 14.082
formula still agrees to within 1% with today’s 
formulas over the range of 15 to 67°C. 35 0.09037 11.065
Illustration 1 shows the temperature 40 0.11351 8.810
dependence of pure water. The conductivity or 45 0.14082 7.101
resistivity of pure water without any impurities 50 0.17269 5.791
is very dependent on temperature. At low 
temperatures close to 0°C the change in 55 0.20945 4.774
conductivity is about 7% per degree Celsius. 60 0.25140 3.978
Clearly, the implementation of pure water 
temperature correction is important. Since 65 0.29875 3.347
work in this area is still ongoing, the 210-C 70 0.35164 2.844
analyzer allows the selection of two pure water 75 0.41017 2.438
temperature compensation formulas, ASTM 
1125 or later ASTM D5391-99 with selectable 80 0.47438 2.108
TC compensation for Acids or Alkalies or 85 0.54440 1.837
Neutral Salts.
90 0.62046 1.612
ASTM 1125 TC Formula 95 0.70303 1.422
This curve is the default curve implemented in 100 0.79303 1.261
the 210-C analyzer. Work done in the 1980’s 
led to the development of these generally- Table 1 ASTM 1125 data
accepted Pure Water Temperature 
compensation values, that were included into 
ASTM standard D 1125-95 (1999).
IC Controls application Notes Issue 4.2 ©IC Controls 2012
Later TC Formula Solute Algorithm Selection
Ongoing work produced later data published The temperature compensation of high-purity 
in ULTRA PURE WATER in December 1994. water changes depending on the chemistry of 
This data presents slightly refined data based the traces of salts or impurities present in it. 
on new research. To give you the greatest To properly correct for this you should select 
flexibility possible the  210-C includes this the solute compensation algorithm that best 
data as a selectable option. matches the chemistry of the water you are 
measuring. Examples; a) Cation Demineralizer 
effluent application would use the Acidic 
algorithm, b) Boiler water with treatment 
byproduct ammonia would use the Basic 
°C µS/cm MΩ·cm algorithm, c) Mixed bed polisher product 
0 0.01162 86.072 water with only traces of salts left would use 
the Neutral salt algorithm.
5 0.01659 60.266
10 0.02312 43.256
15 0.03150 31.751
20 0.04205 23.782
25 0.05512 18.143
30 0.07105 14.074
35 0.09022 11.084
40 0.11298 8.851
45 0.13970 7.158
Illustration 2 Additive sample chemistry compensation
50 0.17071 5.858
Illustration 2 shows how significant the non-
55 0.20637 4.846 linear dependence on temperature for the 
60 0.24697 4.049 different solute compensation algorithms can 
be, that are additive to the Pure Water Formula 
65 0.29280 3.415 selected above.
70 0.34410 2.906 Temperature has a BIG impact on conductivity 
75 0.40110 2.493 readings. At the historical rate, of 2% change 
80 0.46392 2.156 per °C, a 25°C temperature shift can produce a 
50% error if the reading is not compensated. 
85 0.53276 1.877 Since the conductivity of high-purity water has 
90 0.60775 1.645 larger, and non-linear, temperature dependence 
the errors could be huge. For the IC Controls 
95 0.68908 1.451 210-C HPW (High Purity Water) analyzer, the 
100 0.77697 1.287 default TC correction is Auto, Pure Water 
Formula for ASTM 1125, Chemical Solute 
Table 2 Later data, 1994 Algorithm for NaCl (in theory pure water is 
neutral). Both for high accuracy work and high 
purity water applications IC Controls 
recommends the user check the actual 
IC Controls application Notes Issue 4.2 ©IC Controls 2012
chemicals involved and change the solute Linear TC
selection setting if necessary.
The historical temperature compensation is 
Neutral Salt = Default for HPW linear at 2.00%/°C compensation, or can be 
edited to a different value. The LTCC Linear 
The 210-C Pure Water Conductivity Analyzer Temperature Compensation Constant can be 
default temperature compensation is for edited to any desired value.
Neutral Salt (in theory pure water is neutral). 
Samples with a neutral pH close to 7 can select 210-C Start-up Settings
the sodium chloride compensation algorithm. 
In a neutral salt solution the number of The 210-C HPW conductivity analyzer's 
hydrogen and hydroxyl ions are approximately default assumes a sensor with a cell constant 
equal. of 0.01/cm which is stored in its memory. By 
default, the analyzer comes up reading 
This algorithm is usually satisfactory for conductivity in µS/cm. The cell constant of the 
monitoring the effluent of mixed bed ion sensor must match the cell constant stored in 
exchange. Neutral compensation is also the analyzer memory. If other than a 0.01/cm 
applicable to boiling water reactor water cell constant is used, change the constant 
samples because they are normally close to stored by the analyzer so that the analyzer will 
neutral pH. Makeup water and nuclear boiling read properly.
water reactor plant water are untreated and 
neutral mineral traces are the most common 
contaminants.
PURE WATER CALIBRATION
Acidic / Cation Effluent Samples TRACEABLE TO NIST
Samples with strongly dissociating acid traces Conductivity sensor effective surface areas can 
such as hydrochloric acid which completely be changed by contact with the process. At 
dissociates in water should use the acidic high-purity water measurement conditions 
algorithm. cabling capacitance and resistance sometimes 
Cation exchangers used by the power industry influence the readings. IC Controls 
remove chemicals not of interest, and recommends both an air zero calibration and a 
substitute the far more conductive hydrogen. standard calibration of the conductivity sensor 
Electronics rinse after etch, also results in an to determine the effective cell constant. This 
acidic sample, which requires use of acid procedure requires a conductivity or resistivity 
compensation to achieve accuracy. Cation standard from which the effective sensor cell 
conductivity analyzers should also use this constant can be determined, or a second 
solute selection. calibrated sensor and analyzer.
The 210-C HPW conductivity sensor analyzer 
Basic for many Boiler Waters system is most easily calibrated using 100 
Samples with strong base such as sodium µS/cm standard conductivity solution. 
hydroxide which completely dissociates in Alternatively grab-sample analysis verses a 
water should use the basic algorithm. Boiler previously calibrated reference conductivity 
water with treatment byproduct ammonia or meter using an in line flow conductivity sensor 
morpholine would use the basic algorithm. can be used.
Ionic movement, and therefore conductivity, is 
proportional to temperature. The effect is 
predictable and repeatable for most chemicals, 
IC Controls application Notes Issue 4.2 ©IC Controls 2012
although unique to each. In High Purity Water Calibration using 100 µS/cm 
it is of major importance, and IC Controls Standard
recommends the user check the application 
and ensure the appropriate TC Algorithm is in These instructions use an IC Controls 
use. Calibration using the wrong HPW A1400051 Low Range Conductivity 
algorithm can incorporate large errors into the Calibration Kit.
results. The A1400051 is a calibration kit containing 
Overall system accuracy is maintained by solutions and items necessary for calibrating. 
calibrating the sensor and analyzer together in The kit consists of the following items:
a standard close to the expected sample Content Description Qty & Part No. 
concentration. Calibration determines the Size 
effective cell constant of the conductivity 
sensor. The cell constant is affected by the Conductivity standard 2 x 500 A1100161
shape of the sensing surface and electrode 100 µS/cm mL
surface characteristics. The effective cell Demin water 4 x 500 A1100192
constant will change over time as deposits mL
form, and anything else affects either the 
controlled volume or the effective electrode Syringe 1 x 10 mL A7400031
surface area. Polyethylene 2 x 100 A1100007
When using IC Controls 210-C. Output hold graduated cylinders, mL
goes into effect as soon as a calibration is set of 2.
started. The output hold will stay in effect Sensor cleaning 1 A1100016
until a) you select sample, b) no key is pressed brush, ¼ inch
for 15 minutes, c) the power is interrupted so 
the analyzer reboots. Instruction sheet
The output hold feature avoids false alarms Instructions for A1400051 Low-
and erratic signal output caused by a routine 
calibration. Range Cond. Calibration Kit
1. Set up the calibration supplies where you 
Selecting a standard; that is  plan to do the calibration. Lay out the two 
Traceable to NIST graduated cylinders, one for span or high-
end standard, one for low-end standard. Set 
Conductivity standards provide the simplest out the sensor cleaning brush, syringe, 
method of calibrating the analyzer and standards and rinse solutions.
conductivity sensor. The standards most 
commonly used for calibration are: 100 µS/cm 2. Remove the conductivity sensor from the 
at 25°C (77°F) and ASTM “D” standard. For process and examine it for deposits. Use 
NIST Traceability, when ordering also specify demin water to flush away any deposits 
a A1900333 Trace to NIST Certificate, which within the cell measurement area. 
will provide the full Quality record from the Tenacious deposits may require chemical 
Standard purchased to the NIST SRM cleaning, see A1400054 Kit.
(Standard Reference Material) and their lot 3. Pour approximately 75 mL of 100 µS/cm 
number(s). high-end conductivity standard into a 
graduate so it is about three quarters full. 
Lower the conductivity cell into the 
graduate.
IC Controls application Notes Issue 4.2 ©IC Controls 2012
conductivity standard.
Tip: Ensure there are no air bubbles inside The display stops blinking and shows the 
the cell, they will cause low conductivity conductivity of the standard.
readings. Remove by tapping or alternately Note
raise / lower the sensor to flush them out. a) It is possible to repeat or restart the 
4. With the conductivity cell centered and no calibration at any time. Simply press 
air bubbles in the cell, monitor the reading Cancel, then Select to restart or to repeat 
for stability, then calibrate. the calibration.
b)If a problem is detected during 
Note: The reading may gradually change calibration, a caution or error message will 
while the sensor equilibrates to the standard be displayed..
temperature (this may take several hours). 8. Verify your calibration by:
With micro analyzers, the program acts as a) Note the cell constant in menu under cell 
an expert thermal equilibrium detector and constant, and repeat steps 3)& 4) three 
flashes its reading until the temperature times, or until three cell constant readings 
stabilizes. are consistent.
b) Rinse the sensor in demin water.
c) Check with 10 µS/cm low-end standard 
at about 10% of scale using the procedure 
from 3) and 4) above.
Calibration Notes
• Used conductivity standard should be 
discarded because exposure to air and 
contamination causes the conductivity of 
standards to change.
• Make low-end standard by dilution
Example: to 100 mL graduated cylinder add 
7.5 mL 100 µS/cm standard, then top up to 
75 mL to get 10 µS/cm standard.
Illustration 3 sensor positioning • CAUTION: low-conductivity water will 
dissolve CO2 from the air, raising 
5. Select from the list, then change the conductivity 1 to 2 µS/cm, plus leach 
displayed standard value to that of the contaminants in storage from containers, 
standard you are using. and carry over on the sensor, so 10 µS/cm 
6. When using a IC Controls 210-C HPW will likely read 11, 12, or 13 µS/cm 
Press Right to start the calibration. The (possibly even more).
analyzer will display a flashing • If the sensor reads correctly the calibration 
concentration reading. From here on the and sensor condition are good. If the sensor 
calibration process is automatic. reads wrong it may have had trapped 
7. Acting like an analyzer expert, the analyzer bubbles inside, or traces of 100 µS/cm 
will wait until the reading has stabilized, standard. Re-test three times, or until three 
then calculate the cell constant using the readings are consistent; if problem persists, 
temperature-compensated value of the try chemical cleaning.
IC Controls application Notes Issue 4.2 ©IC Controls 2012
• A clean, rinsed and dried conductivity Water), IC Controls recommends use of a 
sensor should read near zero in air. If it second 210-C HPW analyzer and 402-0.01-73 
does not, troubleshoot the sensor, wiring, sensor to determine the actual conductivity of 
and analyzer. the sample.
• Low-conductivity grab samples taken to the 1. Obtain the following materials: a second 
laboratory for calibration checks are not lab calibrated 210-C HPW and 402-0.01-73 
reliable due to CO2 absorption from air. sensor.
• CAUTION: Standards less than 10 µS/cm 2. Record the cell constant of the sensor as 
made in air will dissolve CO2, raising seen by the lab calibrated 210-C HPW 
conductivity 1 to 2 µS/cm, so are analyzer. The cell constant is displayed by 
unreliable. Stored demin will also have selecting Cell Constant, in the calibration 
conductivity readings of 2 or 3 µS/cm due menu.
to chemicals dissolved from containers and 3. Tube up the calibration cell (2nd 402) to the 
should not be used. For 1 µS/cm standards, outlet of your process sensor to get a 
try first triple rinsing all vessels with representative flowing sample from the 
sample of less than 1 µS/cm conductivity, process without exposure to air. (In order for 
then diluting the standard using sample of the procedure to work the sample you are drawing 
less than 1 µS/cm. must be representative of the sample being 
measured by the on-line analyzer.)
Calibration Using ASTM “D” 4. Record the conductivity/resistivity and 
ASTM “D” standard with conductivity 146.93 temperature of the sample as displayed by 
µS/cm at 25 °C can be substituted for 100 the on-line conductivity analyzer.
µS/cm standard in the above calibration 5. Measure the conductivity of the sample 
procedure. When using ASTM “D” Standard using the second 210-C conductivity 
(P/N A1100232) users may wish to follow the analyzer and record the conductivity 
procedures outlined in ASTM D1125 and reading and temperature.
D5391-99.
Note: For accurate results the sample must 
Calibration by Grab-Sample be at the same temperature and the 
This modified grab-sample technique is analyzers must use the same temperature 
quicker and easier if the sensor is not easily compensation method. Allow considerable 
accessible, and with the high probability that time for the calibration sensor to rinse down 
pure water samples of less than 10 µS/cm will and equilibration to the sample level (this 
be changed on exposure to air, it is should be several hours). A stable reading 
recommended. This procedure describes how close to the on-line sensor reading acts as a 
to calibrate the analyzer without taking the good indicator.
sensor out of the process. To calibrate measure 6. Calculate the new cell constant to be 
the sample with a second calibrated analyzer entered into the 210-C analyzer using the 
and flow sensor, similar to ASTM D 5391-99 following formula:
for conductivity/resistivity of a flowing high- lab reading
purity water sample. Since most portable and new cell const= ×old cell constfield reading
laboratory conductivity instruments do not For example, if the 210-C analyzer is 
have flow sensors and use limited 2% per °C reading 8.2 µS/cm, the cell constant (from 
temperature compensation (not acceptable step 2) is 0.01/cm, and the reading from the 
under ASTM D 5391-99 for High Purity second method is 8.9 µS/cm, then the new 
IC Controls application Notes Issue 4.2 ©IC Controls 2012
cell constant becomes Maintaining High Purity 
8.9
new cell const= ×0.01/cm=0.0109/cm Water
8.2
High  Purity  Water  is  expensive  to  produce, 
7. Adjust the cell constant to the new value, which  makes  recovery  and  contamination 
e.g. 0.0109/cm as in the example. The cell prevention  important.  The  largest  source  of 
constant is adjusted by selecting cell  contamination  is  Heat  Exchanger  or 
constant from the menu. Press Enter to go Condenser Leaks. The IC Controls 210-C-C2 
into edit mode, then adjust the displayed with  two  401-0.1  sensors  in  ratio  mode 
value to 0.0109. Press Enter again to exit provides  notice  of  a  leak  (or  pinhole)  in 
edit mode process  heat  exchangers  or  condensers.  401 
Air Zero Calibration Leak Detector sensors are designed for direct in  line  hot  condensate  measurement.  Locate 
It is not necessary to repeat “Air” cal every one  401  probe  in  the  line  after  the  heat 
time a regular calibration is performed. exchanger  or  condenser  and the  other  in  the 
An air calibration should be performed line before the heat exchanger or condenser. A 
anytime a new sensor is installed. When a good  exchanger  or  condenser  will  have  a 
sensor is in air, the conductivity measured by conductivity ratio of 1:1. A leaking exchanger 
the sensor is expected to be zero. It is not or condenser will  develop a 1:1.5 or 1:2 (or 
uncommon to find some small conductivity more) ratio. You get early early leak detection 
signal with the dry sensor in air or even with plus you benefit from an indication of how bad 
no sensor connected at all. This measurement the leak is, so can schedule a sensible repair 
can be due to background noise, lead wire time. As well as lower cost to maintain your 
pickup (antenna effect), grounding problems, High Purity Water purity. 
etc. The air calibration is designed to subtract This same approach can be used to maintain 
the small errors of this interference signal from any process area that has a single feed line and 
the real measurement in order to give a true a single return line.
zero reading.
1. Do the zero cal on a new sensor and its 
wiring.
2. Make sure that the sensor is dry before 
zeroing. The analyzer should be reading a 
low conductivity value.
3. From the menu select conductivity, 
calibrate, air zero. The analyzer will show 
press enter to confirm.
4. When the sensor is ready to be calibrated, 
press Enter.
5. Press Sample. With the sensor still dry and 
in air, the conductivity should read 0.00 
µS/cm.
IC Controls application Notes Issue 4.2 ©IC Controls 2012
To Order the Systems pictured Specify:
High Temperature and Pressure, in line High  
Purity Water Protection, Leak Detection and  
Side stream High Purity monitoring sample  alarm, system components only:
system components only: 210-C HPW-1-8-10-20 (Panel Mount Analyzer) or 
210-C HPW-1-8-10-20 (Panel Mount Analyzer) or 210-C HPW-1-9-10-20 (Pipe/surface Mount)
210-C HPW-1-9-10-20 (Pipe/surface Mount) handles up to 400 PSIG at 200°C
and  402-0.01-72(3M)-73 sensor and  2 only 401-0.1-62-72(3M) sensor
Side stream High Purity monitoring sample  Side stream High Purity Water Protection, Leak  
system assembled on a panel: Detection and alarm, sample system assembled on  
402-0.01-25-73 integrated pure water sampling a panel:
system with 210-C HPW-1-10-20  on a surface 401-0.1-25-76 integrated leak detection sampling 
panel system with 210-C HPW-1-10-20  on a surface 
panel
Direct insertion in line, but retractable for  A1400051 Low Range Conductivity Calibration 
calibration, High Purity monitoring system  Kit.
components only:
210-C HPW-1-8-10-20 (Panel Mount Analyzer) or 
210-C HPW-1-9-10-20 (Pipe/surface Mount) A1100161 Conductivity standard 100 µS/cm, 
and  403-0.01-21-22-72(3M) sensor 500ml bottle.
A1100232 ASTM “D” Standard, 500ml bottle.
A1100192 Demineralized water, 500ml bottle.
Direct in line High Purity Water Protection, Leak  
Detection and alarm, system components only:
210-C HPW-1-8-10-20 (Panel Mount Analyzer) or A1900333 Trace to NIST, Certificates, records 
210-C HPW-1-9-10-20 (Pipe/surface Mount) full calibration to NIST SRM and their lot 
handles up to 400 PSIG at 100°C numbers.
or handles up to 250 PSIG at 150°C *(3M)= 3 meter or 10ft special conductivity cable, suggested length, 
and  2 only 401-0.1-72(3M) sensors can be customized to suit specific need. 
IC Controls application Notes Issue 4.2 ©IC Controls 2012
IC Controls application Notes Issue 4.2 ©IC Controls 2012