PPB Dissolved Oxygen Measurement Calibration and Sampling Techniques
Introduction
The water is used as a rinse agent in the clean room process,
The amount of dissolved oxygen in process water is continually
which is why there is a focus on ever-tightening standards for
gaining importance in many industries as a critical parameter to
controlling dissolved oxygen. Dissolved oxygen, when allowed to
be measured and controlled. The semiconductor and power
remain in solution, can cause oxidation in the mixed bed resins
industries are continuously requiring increased accuracy in
and can then be carried over to the clean room chip
dissolved oxygen detection as lower levels of oxygen are
manufacturing level. Upon start-up of this facility in 1995, there
required in the process water. The purpose of the on-line,
was a dilemma in establishing a baseline for dissolved oxygen
dissolved oxygen measurement is to continuously monitor the
removal. Once a baseline was established, it would have to be
process water to ensure that the level of oxygen is within
accurately verified with a known standard, thus assuring optimum
specifications. The dissolved oxygen concentration is typically
system performance.
measured at multiple points to determine the efficiency of the
means used for oxygen removal - typically some form of
The vacuum degasification system removes the dissolved
mechanical degasification/deaeration and/or chemical injection -
oxygen from the process water (Figure 1). Measurements are
as well as to detect process upsets or leaks. However, plant
taken before and after the degasifiers, as well as on the supply
personnel are often frustrated with the process of trying to obtain
loops feeding the factory. Although the vacuum degasification
quantitative results for the measurement that are useful and
system under peak performance is capable of producing water in
meaningful. Many of the proper techniques used to actually
the 9 parts per billion (ppb) range, many variables must be met in
obtain and correctly measure the dissolved oxygen concentration
order to maintain these operating specifications. The readings
in a representative sample of the process water are not well
after Vacuum Degasifier #1 consistently read within the 5-20 ppb
understood, and the personnel responsible for the measurement
range, while the readings after Degasifier #2 read in the 25-50
are often very distrustful of the instrumentation as a result. When
ppb range. Process streams which should have been identical
these techniques, consisting of proper calibration and sampling
consistently read a difference in dissolved oxygen concentration
practices, are learned and understood, they can be used to
of more than 20 ppb. The sampling lines and instrumentation
effectively discern whether or not the dissolved oxygen levels in
were always suspect since consistent and repeatable results
their process meets the specifications required. A semiconductor
were difficult. In order to ensure that the dissolved oxygen
plant in Austin, Texas is one such example of a site where these
removal system was working correctly, the meters and sample
techniques were effectively utilized to validate their sample lines
lines would have to be proved first. To do so, a procedure was
and measurement instrumentation, and in doing so discovered a
needed to test and prove that the readings were representative of
problem with a process component.
the true oxygen concentrations. This was done by validating
calibration methods and verifying that the sample lines were not
The Problem
The aforementioned semiconductor facility is one of the leaders
in the semiconductor manufacturing industry, and as such
focuses on producing the most advanced product with a major
emphasis on quality. Ultrapure water is one asset that allows this
facility to achieve this with minimal impact to its people and the
environment.
contaminating the reading.
PPB Dissolved Oxygen Measurement - Calibration and Sampling Techniques
2
Calibration
The relationship between oxygen partial pressure and total
Dissolved oxygen probes designed for measurements in the
atmospheric pressure should be understood and incorporated
parts per billion range generate a current proportional to the
into the air calibration in order to minimize calibration error, which
oxygen partial pressure. For the typical levels of oxygen partial
could be as high as 5-10% dependent upon altitude and local
pressure present in the process and calibration mediums used in
weather conditions. Most dissolved oxygen meters that have any
the semiconductor industry, the signal produced by the probe is
sort of advanced air calibration (such as temperature
essentially a linear function of the partial pressure.1 In order to
compensation, which will be discussed in a later section) will be
obtain an accurate representation of the dissolved oxygen,
based upon an atmospheric pressure of 760 mmHg. Most tables
current values must be calibrated to the partial pressures which
of oxygen solubility are referenced to this value.3,4 Because of
they represent. Few dissolved oxygen instruments display the
the change in oxygen partial pressure with changes in
partial pressures of oxygen, however. Rather, the dissolved
atmospheric pressure, a correction must be made when the
oxygen concentration, which is directly proportional to partial
pressure varies from this value. A simple means of incorporating
pressure of oxygen for the range of interest , is the commonly
pressure changes is listed in the “correction factor” shown in
displayed unit of measure, and will be used in the following
Table 1. The value listed is a rough multiplier which can be used
discussion along with partial pressure.
once the initial oxygen concentration is determined based upon
2
temperature and relative humidity. A more accurate calculation
The common calibration method for most dissolved oxygen
for incorporating pressure will be discussed after relative humidity
systems involve exposing the probe in air, since air will always
and temperature effects are investigated.
have a known partial pressure of oxygen dependent upon
atmospheric pressure as well as temperature-dependent
A few newer dissolved oxygen meters contain a pressure
humidity, if present. Air-saturated water can also be used for
sensing device which provides compensation for pressure effects
calibration, but guaranteeing a precise partial pressure of oxygen
when an air calibration is performed. Since most meters do not
in the water is difficult and problematic. Air calibration remains
have this, it is usually necessary to note the average pressure in
the tried and true procedure for calibrating dissolved oxygen
the local vicinity of the probe, which will be mostly altitude-based,
probes. However, air calibration can easily can be done
and adjust the calibration using the simple correction factor or the
incorrectly, yielding significant error if the characteristics of the air
more complex calculation performed later. A mercury barometer
in the immediate vicinity of the probe are not taken into
located in the immediate vicinity of the meter will give a relatively
consideration. It is vitally important that the user understand the
accurate measurement of the local atmospheric pressure if an
effects caused by variations in any of these variables in order to
older meter with no pressure sensor is used.
ensure an accurate and consistent air calibration.
Relative Humidity and Temperature
Pressure
The discussion of pressure effects were based upon atmospheric
The constituents of air have been well defined, and it is known
pressure with dry air (no moisture content). Whenever air
that air contains 20.946% oxygen. Since the total pressure in the
contains a certain amount of moisture, the atmospheric pressure
air is the sum of all of the partial pressures (Dalton’s Law), an
contains another source of partial pressure -- water vapor. If a
atmospheric pressure of 760 millimeters Mercury (mmHg) in dry
comparison of the oxygen partial pressure in air with 100%
air will contain a partial pressure of oxygen (pO2) of
relative humidity and air with 0% relative humidity is done while
approximately 159 mmHg (760 mmHg * 0.20946). Changes in
both are at the same atmospheric pressure, the air with 100%
atmospheric pressure will cause a directly proportional change in
relative humidity will have a lower oxygen partial pressure due to
the partial pressure of oxygen in the air. Atmospheric pressures
the presence of the water vapor pressure (pH2O). Water vapor
will vary depending upon altitude and local weather conditions.
pressure in air varies with temperature, and is well defined.3 The
Some average pressures for varying altitudes are listed in Table
effect of temperature on oxygen partial pressure in moist air is
1.
such that higher temperatures yield lower oxygen partial
3
pressure, while lower temperatures yield higher pressures. This
relationship is shown in Figure 2.
PPB Dissolved Oxygen Measurement - Calibration and Sampling Techniques
3
Note that the effects of relative humidity and temperature can
Equation 1 should be used with air with 100% relative humidity,
cause errors when air calibration is performed in dry air, since
and Equation 2 should be used for air with 0% relative humidity.
most of the current tables and meter temperature compensations
are based on air containing 100% relative humidity. Table 2
Equation 1 (100% Relative Humidity): S = (S’) * (P - p) / (760 - p)
shows both the oxygen concentration, which is linear with the
partial pressure of oxygen, that would be present at 100%
where:
relative humidity and 0% relative humidity. The values only differ
by a few percent in ambient air conditions, and thus is generally
S = Oxygen solubility at barometric pressure of interest
ignored. Most dissolved oxygen meters have temperature
compensation for air at 100% relative humidity, and no manual
S’ = Oxygen in saturation at one atmosphere (760 mmHg) at a
correction is necessary. However, many older meters do not
given temperature
have temperature compensation included, and therefore this
calculation must be done manually. If temperature is not
P = Barometric pressure of interest
compensated for in the calibration, the error can be as much as
20 to 30 % for every 10 degrees difference from 25º C, and
p = Vapor pressure of water at the temperature of interest
therefore temperature compensation is standard on most
dissolved oxygen meters today. Since the effects of relative
Example 1: The user wishes to calibrate a dissolved oxygen
humidity is minimal at all but the highest temperatures, no current
probe in air at an altitude of 3500 feet. The temperature is 30º C,
dissolved oxygen meters incorporate any kind of relative humidity
and the relative humidity is 100%.
sensing device.
At an altitude of 3500 feet, the atmosphere pressure will usually
In order to ensure an accurate temperature and current reading,
be about 668 mmHg (Table 1). The sample temperature is 30º C,
the probe must be exposed to the air for enough time to allow
and the relative humidity is 100%. From water vapor pressure
thermal equilibrium to occur. There are often significant
tables, the water vapor pressure at 30º C is 31.8 mmHg. The
temperature differences between the process water and the
oxygen saturation level at 760 mmHg and 30º C is 7.54 ppm
ambient air. Larger temperature gradients between the two
(Table 2). Substituting these values in the above equation gives
necessitate additional time for thermal equilibrium to take place.
the following:
3
For instance, a 20º C difference between ambient air and
process water can cause a calibration delay of about 30 minutes
S = (7.54) * (668 - 31.8) / (760 - 31.8) = 6.59 ppm
in many probes for the probe to fully equilibrate to ambient
temperature. Since most temperature gradients will not be this
Example 2: Assume the same conditions as in example 1, but
large, allowing approximately 15 minutes is usually a safe
with a relative humidity of 0%. In this case, the value used for the
assumption. It is common for users to calibrate the unit before
oxygen saturation level would be 7.87 (Table 2), not 7.54. The
the dissolved oxygen meter is reading the stabilized temperature
calculation will change since there will be no water vapor
and current value, which can cause significant error since a
pressure.
difference of even 5º C from actual can cause the reading be off
by 5 to 10%. It is often useful to have a calibrated temperature
Equation 2 (0% Relative Humidity): S = (S’) * (P) / (760 mmHg)
sensor, accurate to 1º C or better, at the calibration location to
know when the probe temperature is reading the correct ambient
Substituting the above values into the equation yields the
air temperature.
following:
It is useful to have an equation which can be used to determine
S = 7.87 * (668) / (760) = 6.92 ppm
oxygen concentrations in air based upon temperature, relative
2
humidity, and pressure. Since the full equation is quite lengthy
Note that the multiplier of (668) / (760) is actually the simplified
and complex, two easier versions are presented to the user,
correction factor listed in Table 1 for an altitude of 3500 feet
along with Table 2, to determine the correct oxygen
(0.88). Table 3 lists calibration values for varying temperatures
concentration in air.
pressures at relative humidity levels of 100%.
PPB Dissolved Oxygen Measurement - Calibration and Sampling Techniques
4
Calibration Procedure
Effects such as long recovery times from air calibrations, errors in
The following steps can be followed to ensure an accurate
comparisons between on-line probes and wet chemistry tests,
calibration.
and incorrect readings of the actual process dissolved oxygen
levels are typical examples which affect more sampling systems
1.
2.
3.
4.
5.
Expose the probe to air. Since meters that incorporate
temperature for calibration purposes base the compensation
on 100% R.H. air, the calibration will be most accurate
whenever the air around the probe is high in relative
humidity.
Wait until the dissolved oxygen and temperature readings
stabilize. This usually takes about 5 to 45 minutes,
depending upon the temperature differences between
process water and air, as well as the oxygen difference
between the process and the air. If the meter does not have
a temperature reading, it may not have a temperature sensor
either, in which case the probe will be ready for calibration
as soon as the dissolved oxygen reading stabilizes. When
no temperature reading is available from the meter, the user
should have an accurate temperature sensor to determine
the ambient air temperature for calculation purposes.
Compare the temperature and pressure reading on the
meter to a calibrated temperature and pressure reading in
the same vicinity of the probe. If the meter doesn’t have a
pressure sensor available, use a local mercury barometer to
determine the atmospheric pressure. If a barometer is not
available, just use the value from Table 2 associated with the
altitude at the location of the meter.
If the pressure and temperature agree with the local
readings, then perform the air calibration. If the temperature
and pressure reading on the meter differ significantly
(pressure by more than about 5 mmHg or temperature by
more than about 2º C), recalibrate them, if possible, or adjust
the readings manually. If the temperature and pressure
readings are not included with the meter, the manual
calculations described earlier should be used to determine
the correct calibration value.
Place the probe back in the process. It is useful to adjust the
flow up to 300 ml/min or more for the first few hours in order
to flush out any oxygen that may have become entrained as
a result of the air calibration.
than users know.
Sampling lines often have dead legs (spaces where stagnant
water or air is present), trapped air bubbles, and/or leaks in them.
Deadlegs are found in areas of piping that do not always have
flow through them, causing an area of stagnant water to be
present. This can result in an area of trapped air, which will
cause a seemingly high dissolved oxygen reading. Air bubbles
can be found in piping that is flowing in a downward direction.
The natural buoyancy of air will cause the bubbles to resist the
flow of water in downward flowing piping at lower flow rates.
Deadlegs and air bubbles will eventually dissolve (they will
dissolve faster at higher flow rates), but may take hours or days
to dissolve if the flow rate is low (100 ml/min or less).
While air bubbles will eventually dissolve, leaks will continuously
cause erroneously high readings. While leaks are usually
minimized by higher line pressures due to successive stages of
smaller sampling lines, their presence can still cause large errors
in readings, especially at the low levels of oxygen present in most
power plant and semiconductor process lines. A way of testing
for leaks is to increase the flow by 50 to 100% and observe the
dissolved oxygen reading for the total length of time that it would
take water to travel from the process to the probe. If a drop in
reading is noticed, it may be due to a leak. The flow should be
returned to normal for 10 to 20 minutes, and the test repeated. If
the same drop in reading is noticed again, there is most likely a
leak somewhere upstream of the probe.
Higher flow rates can help to minimize leaks, since higher flow
rates will dilute the oxygen ingress. Leaks can be caused by nonmetallic piping, fittings, rotameters, and even probe mountings.
Flowmeters, a common cause of leaks, can often be placed after
the probe and perform the same function without introducing a
leak until after the probe reading. Non-metallic sample lines have
been observed to allow oxygen ingress even when new, and
often get worse over time, so they should be replaced with
Sampling
stainless steel piping. Loose fittings are also a common source
Correct sampling is perhaps the most misunderstood
for leaks and may need to be redone with additional teflon tape
requirement in obtaining valid dissolved oxygen readings at low
or sealant of some sort. Incorrect mounting of the probes are
ppb levels.
common and can cause leak problems as well. The manufacturer
of the probe should be contacted to ensure that the correct
procedure is being followed for mounting the probe.
PPB Dissolved Oxygen Measurement - Calibration and Sampling Techniques
Sampling for comparison readings with a portable meter should
The sampling lines were entirely stainless steel, but leaks were
always be done in parallel lines and never in series, as one probe
suspected from fittings and sample line flowmeters. Leak testing
will contaminate the downstream reading. Wet chemistry
was done with little change in reading, thus indicating that the
readings should always be done in parallel lines as well. Most
discrepancies between Degasifier #1 and #2 were probably not
users have a separate line for these readings which is turned on
due to sample line leaks. As a precaution, the sampling system
for a few minutes at 200 ml/min or less before the reading is
was further pressurized in order to eliminate any potential leaks
made. Doing such will often result in a higher-than-actual
as a possible point oxygen filtration into the lines. At this point,
reading, since even a few hours at this flow rate may not be
readings were trended and the data logged to pinpoint possible
enough time to totally remove all the entrapped air or air bubbles
discrepancies and changes occurring within the system. From
in the sample line. In addition, a period of time (approximately 5
this information and a new confidence in the sampling system
minutes) is often needed in many sample lines just to ensure that
and analyzers, discrepancies between supposedly identical
the sample contains current process water, and not process
streams pointed to the vacuum pump system supplying the
water from the last test. At a minimum, it is recommended that
degasifiers.
5
the wet chemistry sample line be running for at least four hours at
a high flow rate (300 ml/min or more) before sampling in order to
This system is vital in order to maintain levels of vacuum useful
ensure a good reading. More extensive work on proper wet
to the process, and is assisted by seal water and eduction
chemistry sampling has been reported elsewhere.
4,5
venturis. By checking vacuum levels in the degasifiers and
proving seal water flow rates to the pumps, all indications point to
Results
the eductors at the pumps. It was determined that the cause was
Based on the information provided regarding proper
pressure drops in the eductors, causing ice buildup which
measurement system calibration, a procedure was developed to
plugged the orifice holes, drastically reducing pump performance.
ensure consistent, accurate air calibrations. The meter used
Elimination of this problem caused readings at the outlet of
employs temperature compensation for air with 100% relative
Degasifier #2 to change from the 25 to 50 ppb range to peak
humidity. No pressure compensation was available on the model
performance of about 10 to 15 ppb. This proved beneficial
used, so the air calibration was adjusted manually if pressure
through money savings, system balancing, and improved
deviated from the norm. Complete electronic calibrations were
process quality, which in turn has gained the trust for the
also done on the dissolved oxygen analyzers, with several
instrumentation measuring such a critical parameter in the
discrepancies found and repaired at that time. After full electronic
system. As technology continues to advance, even lower levels
and air calibrations, the meters and probes sampling the outlets
of dissolved oxygen will become more critical to detect for
of Degasifier #1 and #2 were switched. The readings at the
applications in today’s competitive semiconductor market. This
sample points remained the same, verifying that the probes and
means that baselines must first be established for allowable
meters were working correctly. This pointed to the sampling lines
dissolved oxygen concentrations in the process. However,
potentially being the source of the problem.
specifications concerning process equipment and all controlling
variables must be addressed prior to questioning the integrity of
the dissolved oxygen analyzers and sample lines at this
semiconductor manufacturer’s facility.
PPB Dissolved Oxygen Measurement - Calibration and Sampling Techniques
6
Ambient
Air
Water from
UV Sterilizers
Eductor
2
Dissolved
Oxygen #1
1
Vacuum
Degasifier
Vacuum Pumps
Dissolved
Oxygen #2
Water Out
2
Process
Water
1
Figure 1: Dissolved Oxygen Sample Points for Vacuum Degasifier
Calibration
Correction
Altitude
(ft)
Pressure
Factor
-540
775
1.02
Sea Level
760
1.00
500
746
0.98
1000
732
0.96
1500
720
0.95
2000
707
0.93
2500
694
0.91
3000
681
0.90
3500
668
0.88
4000
656
0.86
4500
644
0.85
5000
632
0.83
5500
621
0.82
6000
609
0.80
(mm Hg)
Table 1: Oxygen Value Corrected for Pressure (25º C)4
PPB Dissolved Oxygen Measurement - Calibration and Sampling Techniques
7
180
160
140
Partial Pressure, mmHg
120
100
pH2O
80
pO2, 100% R.H.
60
pO2, 0% R.H.
40
20
0
0
10
20
30
40
Temperature, Degrees Celsius
Figure 2: Partial Pressures of Water Vapor and Oxygen vs. Temperature
50
PPB Dissolved Oxygen Measurement - Calibration and Sampling Techniques
8
Temperature
DO (100% R.H.)
DO (0% R.H.)
Temperature
DO (100% R.H.)
DO (0% R.H.)
(Degrees
Celsius)
(ppm, mg/L)
(ppm, mg/L)
(Degrees Celsius)
(ppm, mg/L)
(ppm, mg/L)
0
14.6
14.66
26
8.09
8.37
1
14.19
14.26
27
7.95
8.24
2
13.81
13.89
28
7.81
8.12
3
13.44
13.53
29
7.67
8.00
4
13.09
13.18
30
7.54
7.88
5
12.75
12.85
31
7.41
7.77
6
12.43
12.54
32
7.28
7.66
7
12.12
12.23
33
7.16
7.56
8
11.83
11.94
34
7.05
7.46
9
11.55
11.66
35
6.93
7.37
10
11.27
11.40
36
6.82
7.27
11
11.01
11.14
37
6.71
7.18
12
10.76
10.90
38
6.61
7.10
13
10.52
10.66
39
6.51
7.01
14
10.29
10.44
40
6.41
6.93
15
10.07
10.22
41
6.31
6.85
16
9.85
10.01
42
6.22
6.78
17
9.65
9.82
43
6.13
6.70
18
9.45
9.63
44
6.04
6.63
19
9.26
9.45
45
5.95
6.56
20
9.07
9.27
46
5.86
6.49
21
8.90
9.11
47
5.78
6.43
22
8.72
8.95
48
5.70
6.36
23
8.56
8.80
49
5.62
6.30
24
8.40
8.65
50
5.54
6.24
25
8.24
8.51
Table 2: Dissolved Oxygen Solubility vs. Temperature2,3
PPB Dissolved Oxygen Measurement - Calibration and Sampling Techniques
9
790
775
760
745
730
715
700
685
670
655
0
15.18
14.89
14.60
14.31
14.02
13.73
13.44
13.15
12.86
12.57
1
14.75
14.47
14.19
13.91
13.63
13.34
13.06
12.78
12.50
12.22
2
14.36
14.08
13.81
13.54
13.26
12.99
12.71
12.44
12.16
11.89
3
13.97
13.71
13.44
13.17
12.91
12.64
12.37
12.10
11.84
11.57
4
13.61
13.35
13.09
12.83
12.57
12.31
12.05
11.79
11.53
11.27
5
13.26
13.00
12.75
12.50
12.24
11.99
11.73
11.48
11.23
10.97
6
12.93
12.68
12.43
12.18
11.93
11.69
11.44
11.19
10.94
10.70
7
12.60
12.36
12.12
11.88
11.64
11.40
11.15
10.91
10.67
10.43
8
12.30
12.07
11.83
11.59
11.36
11.12
10.89
10.65
10.41
10.18
9
12.01
11.78
11.55
11.32
11.09
10.86
10.63
10.40
10.17
9.94
10
11.72
11.50
11.27
11.04
10.82
10.59
10.37
10.14
9.92
9.69
11
11.45
11.23
11.01
10.79
10.57
10.35
10.13
9.91
9.69
9.47
12
11.19
10.98
10.76
10.54
10.33
10.11
9.90
9.68
9.47
9.25
13
10.94
10.73
10.52
10.31
10.10
9.89
9.68
9.47
9.26
9.04
14
10.70
10.50
10.29
10.08
9.88
9.67
9.46
9.26
9.05
8.85
15
10.47
10.27
10.07
9.87
9.67
9.46
9.26
9.06
8.86
8.65
16
10.25
10.05
9.85
9.65
9.45
9.26
9.06
8.86
8.66
8.46
17
10.04
9.84
9.65
9.46
9.26
9.07
8.87
8.68
8.48
8.29
18
9.83
9.64
9.45
9.26
9.07
8.88
8.69
8.50
8.31
8.12
19
9.63
9.45
9.26
9.07
8.89
8.70
8.51
8.33
8.14
7.95
20
9.44
9.25
9.07
8.89
8.70
8.52
8.34
8.15
7.97
7.79
21
9.26
9.08
8.90
8.72
8.54
8.36
8.18
8.00
7.82
7.64
22
9.07
8.90
8.72
8.54
8.37
8.19
8.01
7.84
7.66
7.48
23
8.91
8.73
8.56
8.39
8.21
8.04
7.86
7.69
7.52
7.34
24
8.74
8.57
8.40
8.23
8.06
7.89
7.72
7.55
7.38
7.20
25
8.58
8.41
8.24
8.07
7.90
7.74
7.57
7.40
7.23
7.06
26
8.42
8.26
8.09
7.92
7.76
7.59
7.43
7.26
7.10
6.93
27
8.28
8.11
7.95
7.79
7.62
7.46
7.30
7.14
6.97
6.81
28
8.13
7.97
7.81
7.65
7.49
7.33
7.17
7.01
6.85
6.69
29
7.99
7.83
7.67
7.51
7.35
7.20
7.04
6.88
6.72
6.57
30
7.85
7.70
7.54
7.38
7.23
7.07
6.92
6.76
6.61
6.45
31
7.72
7.56
7.41
7.26
7.10
6.95
6.80
6.64
6.49
6.34
32
7.58
7.43
7.28
7.13
6.98
6.83
6.68
6.53
6.38
6.22
33
7.46
7.31
7.16
7.01
6.86
6.71
6.57
6.42
6.27
6.12
34
7.34
7.20
7.05
6.90
6.76
6.61
6.46
6.32
6.17
6.02
35
7.22
7.07
6.93
6.79
6.64
6.50
6.35
6.21
6.06
5.92
36
7.11
6.96
6.82
6.68
6.53
6.39
6.25
6.11
5.96
5.82
37
6.99
6.85
6.71
6.57
6.43
6.29
6.15
6.00
5.86
5.72
38
6.89
6.75
6.61
6.47
6.33
6.19
6.05
5.91
5.77
5.63
39
6.79
6.65
6.51
6.37
6.23
6.10
5.96
5.82
5.68
5.54
PPB Dissolved Oxygen Measurement - Calibration and Sampling Techniques
10
40
6.68
6.55
6.41
6.27
6.14
6.00
5.86
5.73
5.59
5.45
41
6.58
6.44
6.31
6.18
6.04
5.91
5.77
5.64
5.50
5.37
42
6.49
6.35
6.22
6.09
5.95
5.82
5.69
5.55
5.42
5.28
43
6.39
6.26
6.13
6.00
5.87
5.73
5.60
5.47
5.34
5.20
44
6.30
6.17
6.04
5.91
5.78
5.65
5.52
5.39
5.25
5.12
45
6.21
6.08
5.95
5.82
5.69
5.56
5.43
5.30
5.17
5.04
46
6.12
5.99
5.86
5.73
5.60
5.47
5.35
5.22
5.09
4.96
47
6.03
5.91
5.78
5.65
5.53
5.40
5.27
5.14
5.02
4.89
48
5.95
5.83
5.70
5.57
5.45
5.32
5.19
5.07
4.94
4.82
49
5.87
5.75
5.62
5.49
5.37
5.24
5.12
4.99
4.87
4.74
50
5.79
5.66
5.54
5.42
5.29
5.17
5.04
4.92
4.79
4.67
Table 3: Oxygen Concentration (ppm) for varying pressures (mmHg) andtemperatures (Degrees Celsius) at 100% Relative Humidity
PPB Dissolved Oxygen Measurement - Calibration and Sampling Techniques
More Information
For more information on using Dissolved
Oxygen Measurement, visit
www.honeywellprocess.com, or contact your
Honeywell account manager.
Honeywell Process Solutions
Honeywell
1250 West Sam Houston Parkway South
Houston, TX 77042
Honeywell House, Arlington Business Park
Bracknell, Berkshire, England RG12 1EB UK
Shanghai City Centre, 100 Junyi Road
Shanghai, China 20051
www.honeywellprocess.com
SO-13-19-ENG
January 2013
© 2013 Honeywell International Inc.
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