The reliability and accuracy of the Kohmyr ECC ozone sonde are determined. Emphasis is placed on establishing and testing for leak-free connections and stable pump flow rates as well as properly adjusting the pumping pressure. Calibration of the Kohmyr ECC ozone sondes and Dasibi monitors is described. Raw ordinate data and ozone connection data are presented in tabular form. The results of a linear regression treatment of the sonde-indicated ozone concentration vs. Dasibi readings for each switch position are included along with averages of the regression parameters over the six sequencing switch positions. It is suggested that sondes and Dasibi monitors be individually calibrated before flight

Bandy, A. R.

Torres, A. L.

English

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https://ntrs.nasa.gov/search.jsp?R=19760007590 2020-03-22T18:17:45+00:00Z
December 1975
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DEPARTMENT OF CHEMICAL SCIENCES
SCHOOL OF SCIENCES AND HEALTH PROFESSIONS
OLD DOMINION UNIVERSITY
NORFOLK, VIRGINIA
PEFFORMANCE TESTS ON THE KOHMYR ECC OZONE
SONDE Final Technical Report, 1 Fe F. - 31
Dec. 1975 (Old Dominicn Univ. Research
Foundation)	 12 p HC $3.5C	 CSCL 1`"4A
63/46
PERFORMANCE TESTS ON THE KOHMYR ECC OZONE SONDE
By
A. R. Bandy
and
A.L. Torres
Final Technical Report
Prepared for the
National Aeronautics and Space Administration
Wallops Flight Center
Wallops Island, Virginia
Under
Grant NSG 6002
February 1 - December 31, 1975
N76-14576
uric Ids
J6791
r
PERFORMANCE TESTS ON THE KOHMYR ECC OZONE SONDE
By
A. R. Bandyl and A. L. Torresl
This report contains the results of a study carried out to provide
information on the reliability and accuracy of the Kohmyr ECC ozone sonde
(ref.1) as manufactured by Science Pump Corporation  and flown by the NOAA
Weather Station, Wallops Island, Virginia. The study was made during the
period of August 8-15, 1975, in cooperation with NOAA Weather Station and
Wallops Station NASA personnel.
After minor repairs, the Weather Station's Dasibi Environmental Corpora-
tion ozone monitor was adjusted to operational tolerances, following the
procedures outlined in the manual provided with the instrument. This ozone
monitor and another Dasibi monitor from the Old Dominion University labora-
tory were then connected to a common ozone source for an intercomparison
of calibrations. Agreement within + 2 ppbv was observed over the range
0-500 ppbv.
The ECC ozone sonde preparation procedure described in the manufacturer's
manual (ref.3) includes some checks on sonde performance. Additional emphasis
should be placed on establishing and testing for leak-free connections and
stable pump flow rates.
As indicated by the manufacturer (ref.3), pump motor regulation breaks
down at voltages less than six volts. The magnitude of this effect was
determined experimentally and found to be quite large (fig.l). This could
be of particular significance towards the end of a flight, or in cases where
the current drain on the battery is unusually high.
Emphasis should also be placed on properly adjusting the pumping pressure.
As shown in figure 2, the flow rate is acutely sensitive to pump pressure
setting at pressures less than three inches of mercury. Higher pressures
1 Present address: Chemistry Department, Drexel University
Philadelphia, PA 19104
2 Science Pump Corporation, 1431 Ferry Avenue, Camden, N. J. 08104
r	 ^^
should be avoided, however, because of the possibility of excessive current
drain on the batteries.
To check the calibration of the Kohmyr ECC ozone sondes, two ozone
sondes were prepared for operation according to the manufacturer's instruc-
tions (ref.3). Each ozone sonde was then connected to 1680 mHz radiosondes
which telemetered ozone data to a ground-based receiving station. The data
was recorded on strip chart recorders in the normal fashion (ref. 3). Chart
ordinate data was transformed to ozone concentration data as outlined in
reference 3, except that S = 294 s/k replaced the equation S = 314 s/k
found in Appendix L of reference 3. This change was recommended by Weather
Station personnel because of design changes in the radio sondes occuring
since publication of the manufacturer's instruction.
Raw ordinate data are shown in tables 1 and 2 for each of the sequencing
switch positions. Ozone concentration data calcula.ced from the ordinate
data in tables 1 and 2 are given in tables 3 and 4. The results of a linear
regression treatment of the sonde-indicated ozone concentration vs Dasibi
readings for each switch position are included in these tables, along with
averages of the regression parameters over the six sequencing switch posi-
tions.
For sonde 2A085, the six slopes obtained from the regression analysis
of the individual switch positions are not statistically different. The
mean of the six slopes was 0.762 + 0.90, with an average uncertainty in
each of the individual slopes of 3%.
For sonde 2A098, the mean value of the six slopes was found to be 0.766
+ 2.7%, with an average uncertainty in the individual slopes of 1.7%. This
indicates a possibly real statistical difference between switch positions,
perhaps as a result of differing contact resistances.
The averages of the six intercepts obtained for each sonde are clearly
non-zero and different (9.46 = 34% for sonde 2A085 and -4.34 = 49% for sonde
2A098). For either of the sondes, the six intercepts are probably not
statistically different.
2
CONCLUSIONS AND REMS ENDAVONS
The agreement between the average slopes found for each of the two
ozone sondes (0.762 and 0.766) is quite good. In view of the relative
uncertainties associated with each average slope (0.9% and 2.7a), however,
the agreement is probably fortuitous.
Both slopes are significantly different from the theoretical value of
0.987 predicted on the assumption of exact agreement between sonde ozone
values and Dasibi values and, also, assuming accurate Dasibi calibration.
(The nonunity slope is a result of different measurement units; Dasibi
readings in ppbv and sonde values in umb). The slope errors are probably
not as large as they appear because of uncertainties in the calibrations
of Dasibi instruments. Preliminary studies carried out in Old Dominion
University laboratories have shown the Dasibi to indicate ozone concentra-
tions about 15% higher than values measured by the neutral buffered KI
technique designated by EPA as a reference method (ref.2). The apparent
error in the slopes may thus be only about half of that indicated by
inspection of the slope values reported.
In view of the importance of obtaining accurate stratospheric ozone
measurements, it is suggested that sondes be indiv-idually calibrated
before flight. This could be accomplished using a stable ozone source in
conjunction with the Dasibi monitor. The Dasibi, in turn, should be
subjected to a careful calibration by two independent methods such as the
gas-phase titration method (ref-4), traceable to weight and volume standards,
and the neutral buffered KI method (ref-2).
The nonzero intercepts observed from each sonde are probably due to
errors in the background current attributed to oxygen. Some consideration
should possibly be given to modifications in the ozone-destruct filter
during the background current measurements, in order to remove reactive
interferents.
3
REFERENCES
1. W. D. Kohmyr and T. B. Harris, Development of an ECC ozone sonde,
NOSS Tech. Rept. ERL 200 - APCL 18 (1971).
2. National primary and secondary ambient air quality standards,
Federal Register 36, Part II, April 30, 1971.
3. Instruction manual for model ECC-LA electrochemical concentration
cell ozone sonde, Science Pump Corp. 1431 Ferry Avenue, Camden, NJ
08104.
4. J. A. Hodgeson, R. E. Baumgardner, B. E. Martin and K. A. Rehne,
Stoichrometry in the neutral iodometric procedure for ozone by
gasphase titration with nitric oxide, Anal. Chem. 43, 1123 (1971).
4
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0	 1	 2	 3	 4	 S	 6
PUMP SUPPLY VOLTAGE D.C.
Figure 1. Sonde flow rate as a function of pump
voltage (Sonde 2A085).
5
ij	 ?	 I
240
220
200
s
U
v
3
0
 
180
F
a
a
160
140
120
2.0	 2.2	 2.4	 2.6	 2.9	 3.0	 3.2	 3.4
PUMP PRESSURE (inches Hg)
Figure 2. Sonde flow rate as a function of pump pressure
(Sonde 2A085).
6
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Table 1. Raw Calibration data for 2AO98 Ozone Sonde *
1031
**
Z+ 01 Tb$ 02 03 0# 04 05 06
0 39.0 75.8 75.8 43.0 42.2 63.2 40.5 40.2 41.2
0 39.0 75.8 75.8 42.8 42.5 63.2 40.0 40.2 41.0
0 39.0 75.8 75.8 41.5 41.5 63.5 41.5 40.8 41.0
20 39.2 75.8 75.8 42.0 43.0 63.8 42.8 43.0 44.0
20 39.2 75.9 75.9 44.5 44.5 63.9 43.5 43.5 44.7
50 39.6 76.0 76.0 44.8 44.8 64.0 48.5 51.8 51.5
62 39.8 76.0 76.0 50.5 50.2 64.2 50.0 50.0 50.5
65 39,8 76.0 76.0 50.8 51.0
104 39.8 76.0 76.0 55.5 55.5 64.5 55.2 55.3 55.6
107 39.9 76.0 76.0 55.8 55.8 64.8 55.8
166 40.0 76.2 76.2 63.2 63.5 65.0 63.5 63.5 64.0
172 40.0 76.0 76.0 64.2 64.0 65.0 61,,0 64.0
324 40.0 76.2 76.2 85.2 85.2 65.5 85.2 85.2 85.5
220 40.1 77.5 77.5 81.5 77.5 65.5 74.5 74.0 73.8
223 40.2 76.2 76.2 74.0 74.0 66.0 74.2 74.2 74.8
231 40.2 76.0 76.0 75.2 75.2 66.5 75.8 75.8 75.9
231 40.2 76.0 76.0
* All ozone sonde data is in chart ordinate units with fullscale at 95
** Ozone in ppb obtained with Dasibi ozone monitor
+ Zero reading
# Electronic internal calibration
$ Box temperature
7
Table 2. Raw Calibration data for 2AO85 Ozone Sonde*
03 **	 Z+	 018	 Tb	 02	 03	 C#	 04	 05	 06
0 39.5 39.8 75.8 40.0 40.2 66.4 39.5 40.2 41.0
0 39.2 39.7 75.8 40.0 40.2 66.6 40.1 40.2 41.5
17 39.9 40.0 75.6 40.2 40.4 67.0 42.5 43.2 44.2
20 40.0 44.0 75.8 44.5 44.8 67.2 44.0 44.2 44.9
20 40.0 44.2 75.9 44.8 45.0 67.2 47.0
62 40.0 51.6 76.0 51.2 51.3 67.8 50.8 51.0 51.4
66 40.1 51.2 76.0 51.5 51.5 67.8 54.8
103 40.2 57.0 76.0 56.5 57.0 68.0 57.0 57.0 57.2
107 40.2 57.2 76.0 57.8 57.8 68.4 58.0
173 40.8 66.2 76.2 67.5 67.0 69.2 67.0 67.2 67.2
323 39.2 87.2 87.2 87.8 68.8 86.3 87.6 87.6
* All ozone sonde data is in chart ordinate units with fullscale at 95
** Ozone in ppb obtained with Dasibi ozone monitor
+ Sonde electronic zero
# Electronic internal calibration
$ Box temperature
8
Table 3. Comparison of Dasibi and ECC ozone monitoring devices for sonde
N2A08S
Dasibi (ppb)
	 ECC Sonde (um bar)
1 2
Contact Nimber
3	 4 '	 5 (	 6
0 2 3 4	 0 4 9
0 1 3 4	 3 6 12
17 19 2S
20 23 26 28	 23 2S 29
62 6S 63 64	 61 62 64
103 94 91 94	 94 94 95
107 93 97 97	 98
173 136 143 140	 140 141 141
323 252 252 2SS	 248 254 254
intercept 7.90 8.56 •10.2 3.51 8.S9 13
slope 0.765 0.765 0.767 0.760 0.768 0.149
std error 6.67 5.92 5.S2 6.91 13.7 3.31
error-intercept 3.28 2.06 2.72 3.40 6.29 1.S
error-slope 0.023 0.015 0.0192 0.024 0.046 0.011
corr. coef. 0,9973 0.9976 0.9981 0.9970 0.9880 0.9993
Averages over the 6 data sets*
intercept 9.46 ± 1.89
slope 0.762 + 0.007
std error 7.00 + 3.52
intercept error 3.2 +	 1.67
slope error 0.023 + 0.013
corr. coef. 0.9962 + 0.041
* Errors given here are standard deviations for the six data sets.
9
1	
l_
Table 4. Compb son of Dasibi and ECC ozone monitoring devices for sonde #2A098
Dasibi (ppb)	 ECC Sonde (um bar)
Contact Number
3 4
-1 -12
1 -15
-6 -6
12 6
44 44
50
	78 	 78
	
124	 129
	
234	 234
5	 6
	-14 	 -7
	
-15
	 -9
	
-10
	 -9
	
6	 10
44
	
75	 77
	
121
	 124
	
124
	 124
	
234	 236
1
	
2
	
0
	
0	 15
	
0	 -3
	
3
	
0	 -4	 -6
	20	 12	 12
	
62	 49	 47
	
65
	
49	 49
104
	
108
	
80	 78
166
	172	 125	 125
	
324	 233	 234
intercept -1.46	 0.32 -0.788 -8.23 -9.83 -6.07
slope 0.752	 0.745 0.743 0.787 0.789 0.777
std error 4.3
	
4.71 3.8 6.1 5.73 4.52
error-intercept 1.71	 2.02 1.64 2.74 2.59 2.03
error-slope 0.011	 0.013 0.011 0.016 0.015 0.012
corr. coef. 0.9988	 0.9986 0.9991 0.9981 0.998 0.9988
Averages over t. e 6 data sets
intercept -4.34 ± 4.26
slope 0.766 ± 0.021
std error 4.8 ± 0.88
intercept error 2.12 ± 0.45
slope error 0.013 ± 0.002
corr.	 coef. 0.9986 ± 0.0004
10


Performance tests on the Kohmyr ECC ozone sonde

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