-------
This report was furnished to the
Air Pollution Control Office in
fulfillment of Contract No.
CPA 70-27 by the Research Tri-
-------
CHEMILUMINESCENT OZONE METER
Model EU-525-08
Engineering and Environmental Sciences Division
Research Triangle Institute
Post Office Box 12194
-------
FOREWORD
This report describes the results of a program to design, construct
calibrate and field test an ozone-specific instrument using a chemilum-
inescent principle. The work has been monitored by Mr. E. R. Lozano and
Mr. Frank McElroy, Air Pollution Control Office.
The work was performed in the Engineering and Environmental
Sciences Division, Dr. R. M. Burger, Director. Project Leader was
Mr. J. B. Tommerdahl. Mr. A. H. Truckner fabricated and tested the
basic instrument. Mr. S. R. Stilley wired the amplifier, signal
conditioner and timing/control unit. Mr. R. B. Strong calibrated
the system and conducted detailed performance tests on the system,
amplifier and signal conditioner unit. Mr. C. E. Decker contributed
to the overall program in many areas.
Some of the basic design of the instrument was carried out
under a program under contract with the Air Pollution Control Office
(Contract CPA-22-69-7).
-------
INSTRUMENT IDENTIFICATION AND SPECIFICATIONS
Ozone Meter: Model EU-525
Serial No. 525-08
Photomultiplier Tube:
Type - EMI-9558C
Serial No. 20175
HV 1090
Gain = 200 A/L
Dark Current = 0.8 nA (Mfg. Rating)
Dark Current ?= 1.5 nA (Measured)
HV Supply: Power Design'Model 2K-10
Serial No. 002066
Air Flow Setting:
69
12 vdc Supply: Deltron Model C12-2.8
Serial No. 41605
+15 vdc Supply: HP Model 60155C
Serial No. 961039
-------
TABLE OF CONTENTS
Section Page
1.0 INTRODUCTION 1
2.0 OZONE METER FUNCTIONAL AND OPERATIONAL CHARACTERISTICS 3
2.1 Theory of Operation 3
2.2 Functional Description 3
2.3 Physical Description 6
2.4 Instrument Specifications 8
2.5 Front Panel Controls and Indicators 9
3.0 DETAILED SYSTEM DESCRIPTION 15
3.1 General 15
3.2 Plumbing Subsystem 15
3.3 Detector 19
3.4 Calibration Unit 26
3.5 Timing and Control Unit 33
3.6 Linear Amplifier 36
3.7 Signal Conditioner 43
APPENDICES
A. INSTALLATION AND OPERATION
B. MAINTENANCE, CALIBRATION AND ADJUSTMENT PROCEDURES
C. PARTS LIST
D. SUBSYSTEM MANUALS
E. ENGINEERING DRAWINGS
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LIST OF FIGURES
Figure Page
1 OZONE METER FUNCTIONAL DIAGRAM 4
2 FRONT PANEL VIEW OF OZONE METER (WITH HV POWER SUPPLY 7
COVER REMOVED)
3 REAR PANEL VIEW OF OZONE METER 10
4 MAIN CHASSIS LAYOUT 11
TOP AND REAR VIEW OF CHASSIS 12
LEFT AND RIGHT SIZE VIEWS OF CHASSIS 13
(d)
6 AC AND DC POWER DISTRIBUTION 14
7 PLUMBING SUBSYSTEM 16
8 PLUMBING SUBSYSTEM PARTS LAYOUT 17
9 DETECTOR ASSEMBLY 20
10 AIR FLOW PATTERN IN DISC CHAMBER 21
11 PM TUBE HOUSING WIRING DIAGRAM 23
12 INTERLOCK CIRCUIT 27
13 CALIBRATION UNIT (TOP VIEW) 28
14 OZONE CONCENTRATION VERSUS APERTURE SETTING 29
15 OZONE CONCENTRATION AS A FUNCTION OF LAMP CURRENT AND 31
FLOW RATE
16 CALIBRATION LAMP CURRENT VERSUS LAMP VOLTAGE 32
17 CALIBRATION UNIT, IN SITU CALIBRATION 34
18 TIMING CONTROL CIRCUIT 35
19 PHOTOMULTIPLIER TUBE LINEAR AMPLIFIER 37
20 AMPLIFIER OUTPUT VOLTAGE VERSUS INPUT CURRENT FOR LINEAR 39
RANGES
-------
Figure Page
21 FREQUENCY RESPONSE OF AMPLIFIER FOR VARIOUS GAIN 41
SETTINGS
22 AMPLIFIERS I0~7 AMP FULL SCALE, OUTPUT SENSITIVITY XI 42
23 SIGNAL AND TIMING WAVEFORMS 44
24 BASIC SIGNAL CONDITIONING CIRCUIT 45
25 SIGNAL CONDITIONER CIRCUIT 47
-------
1.0 INTRODUCTION
The Research Triangle Institute has, under Contract CPA 70-27
with the Air Pollution Control Office, conducted a program to design,
conatruct, calibrate, and field test an o::one-specific instrument
using a chemiluminescent principle; the unit is intended, ultimately,
for CAMP stations.
This document is a combined final report for the project and an
instruction manual for the ozone instrument, since a majority of the
information is pertinent to both. Two separate attachements complete
the documentation; these are a set of engineering drawings for the
machine shop fabricated parts and a subsystem manual comprised of
instruction sheets and manuals for the individual commercially procured
units such as the high voltage supply and PM tube housing. Thus this
is, in general, a comprehensive engineering description of the design,
construction details, calibration techniques and operational charac-
teristics; of the ozone monitor. Material essential in an instruction
manual has been expanded, particularly with respect to the design,
testing, and operational characteristics.
The ozone meter developed operates on the chemiluminescent prin-
ciple. When ozone reacts with certian organic compounds, the reaction
o
produces a minute luminescence in the 5800 A region which can be
measured by means of a sensitive photomultiplier tube and dc amplifier.
The chemiluminesence principle for ozone measurement has the advantage
of being essentially specific for ozone for the expected concentrations
of other pollutants.
The ozone meter was designed as a laboratory instrument for the
-------
the meter is considerably more sophisticated in design than would
be necessary for a meter that is designed as a production unit.
This versatility in design provides for a wide latitude of test
conditions.
A functional description of the ozone monitor is given in
Section 2.0; and a detailed description of the design for the
various sub-assemblies are presented in Section 3.0. Various
details concerning parts list, installation and maintenance of
the instrument, calibration procedures, and operation procedures
-------
2.0 OZONE METER FUNCTIONAL AND OPERATIONAL CHARACTERISTICS
2.1 Theory of Operation
The principle on which the chemiluminescent ozone meter
operates is as follows: when ozone reacts with certain organic
compoundss a minute amount of light is emitted. The amount of light
is directly proportional to the ozone concentration, and the wave-
length of the emitted light is a function of the organic compound
or dye used in the formation of the chemiluminescent disc. Gases
to be sampled are passed over a disc coated with the dye. The emitted
light resulting from the reaction with ozone is detected by means of
a sensitive photo-detector.
2-2 Functional Description
A functional diagram of the ozone meter is shown in Figure 1.
The basic element of the system is the chemiluminescent disc and
photo-detector assembly. The gases to be sampled are metered at a
constant flow rate across the disc. The emitted light resulting from
the reaction of ozone with the chemiluminescent material is monitored
by the photomultiplier tube.
The system has essentially three modes of operation. During the
MEASURE mode gases are pulled through the sample-gas inlet, and then
passed over the disc. During the CALIBRATE mode the sample-gas inlet
is closed and the calibrate line is opened by means of electrically
actuated solenoid valves. Air which enters the calibrate line passes
through a filter which removes contaminants and destroys any ozone
-------
LAMP
CONTROL
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EXHAUST
-------
as it passes through the calibration unit by exposing the air stream
\
to an ultra-violet light source. A calibrated aperture control
facilitates varying the ozone concentration. A front panel control
and meter provides for lamp current control and monitoring, respectively.
During the PURGE mode, the unit operates as in the CALIBRATE mode,
except the calibrate lamp shutter remains closed.
The gases are metered at a constant flow rate of 200 ml/min
through the disk chamber by means of control valves, a flow meter
and pump. The flow meter and vernier control valves are located
on the front panel of the instrument. The timing and control unit
provides the necessary switching voltages for actuating the various
solenoids. Selection of operating modes is made by means of front-
panel push-button switches.
The light emission from the disk is detected by means of a
sensitive photomultiplier tube. The output of the PM tube is
amplified and presented on a panel meter and at a recorder output
connector. Five linear-decade current ranges are provided. Contin-
uously variable controls are provided for span and zero adjustment.
A time-constant control is incorporated in the amplifier which
facilitates smoothing of the analog data. A manually operated shutter
incorporated in the disk chamber allows for monitoring of the PM tube
dark current. High voltage for the PM tube is provided by a well
regulated, adjustable HV supply.
The output signal-to-dark current ratio for a given concentration
of ozone is a direct function of the sensitivity of the disk and the
-------
of the emitted light. Since the dark current and the quantum efficiency
vary considerably from tube to tube one may expect a factor of 10 or
more in this ratio. With tube selection this may be reduced to a 10-20%
variation from unit to unit.
The system design includes two selectable sampling modes; SAMPLE-I
is continuous sampling while SAMPLE-II inserts a PURGE mode for a 30
min period of time, every 12 hours. The sampling-mode consists of a
75 sec-measure, 75 sec-purge, 75 see-calibrate, and 75 sec-purge cycle.
In addition, push-button actuated modes are available'for operating
continuously in the RUN, CALIBRATE, or PURGE modes; these facilitate
test and calibration procedures. An EXTERNAL mode is provided for
remotely controlling the operational mode of the instrument.
The output signal from the amplifier is provided at an output
connector and at the input to the signal conditioner. This latter
unit accepts the sampled signal and essentially provides an output
signal, e , which is
m-p
Q =: *
o c-p
where m - is the measure signal value
c - is the calibrate signal value, and
p - is the purge signal value.
2.3 Physical Description
A front panel view of the ozone meter illustrating the type
and location of all controls, meters, etc., is shown in Figure 2. The
cover for the HV supply, which is normally in place, is shown removed
r
-------
-------
There are two basic units, the main chassis and the HV power
supply. The latter is located in the bottom of the cabinet. The
main chassis is mounted on chassis slides and may be readily pulled
out on the chassis slides for adjustment and testing purposes. A
rear view of the instrument is shown in Figure 3. A plan view of
the main chassis is given in Fig. 4, showing the relative positioning
of the major components and assemblies. Top and rear photographs
of the chassis are shown in Fig. 5(a) and (b), respectively. Side
views of the chassis are shown in the photographs in Fig. 5(c) and (d).
Both the main chassis and HV power supply fit into the standard
19" width cabinet. The overall physical dimensions of the instrument
are as follows:
Height - 47 cm,
Width - 50 cm,
Depth - 58.5 cm,
Weight - 68 kg.
The unit requires approximately 300 watts of power from a 115 V,
60 Hz single phase source. A block diagram illustrating the AC and
DC power distribution is given in Figure 6.
2.4 Instrument Specifications
SYSTEM:
Dynamic Range - 0.001-2.0 ppm
Resolution - 1 ppb
Minimum Detectable Level - 1 ppb
Accuracy - + 10% at time of calibration, with respect to values
obtained by KI technique (See Section B-ll)
Stability of calibration signal - approx. 1.5%/volt of line voltage
Calibration - nominal range 0.1-0.2 ppm
internally adjustable 0-0.1 ppm
Output - front panel meter 0-10 units
-------
AMPLIFIER;
Output Meter - full scale value indicated by SENSITIVITY and
FS OUTPUT control settings
Sensitivity - linear - 10~9 amps, FS
10"8 "
10"7 "
10-6
10~5 " "
-9
Stability - linear - 0.01% perฐC; 1% per month (for 10 amp range)
2.5 Front Panel Controls and Indicators
MODE CONTROLS; (Lamps indicate mode of operation)
Ext. - external timing control
Cal. Cont. - continuous CALIBRATE
Meas. Cont. - continuous RUN
SAMP. I - five minute cycle; 75 sec measure, 75 sec purge,
75 sec calibrate, 75 sec purge
SAMP. II - same as Samp I, except a 30 min purge mode is inserted
once every 12 hours
AMPLIFIER:
Span - modifies full scale sensitivity by factor indicated
Time Constant - normal, 1 sec, 2 sec, 4 sec R
Zero - provides dark current offset control from 0-10 amps
LAMP CURRENT - controls calibration lamp current
ELAPSED TIME METER - hours and 1/10 hours, actuated during power ON
condition
FLOW CONTROL - valve and flowmeter for flow control and monitoring
SHUTTER - (Lamps indicate shutter position) open for operation; close
for dark current check and disk removal/replacement
DISK ACCESS DOOR - allows removal/replacement of disk
INTERLOCK SYSTEM - indicates shutter control status; warning buzzer when
disk access door opened without fully closing shutter
HV POWER SUPPLY;
Power Switch - ON position
HV Controls - normally set for value which yield PM tube gain = 200 A/L
Cover - normally left in place
AC POWER - single switch turns entire unit on
\ 9
I
-------
REAR ACCESS DOOR
FAN
10:'.V
1
PUMP
BYPASS
O
o o
SIG COND
OUTPUT OUTPUT
SAMPLE
INLET
EVENT
MARKER
AC POWER
CABLE
i
L :
FIGURE 3, REAR PANEL VIEW OF OZONE METER
-------
SAFETY CHAIN ATTACHMENT POINT
+ 12 VDC
POWER SUPPLY
(+15 Vdc Supply)
j (SIGNAL
COND.
UNIT)
UV
LAMP
XFMR
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A'C
PdwER
STiRIP
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REAR
j
TIMER AND CONTROL
UNIT ASSEMBLY
SAMPLE
SOL
VALVE
CAL
SOL
VALVE
PUMP
1
CALIBRATION UNIT
AMPLIFIER
ASSEMBLY
r
DETECTOR
ASSEMBLY
FRONT
( ) indicates unit in dotted lines which are on a 2nd level
FIGURE 4. MAIN CHASSIS LAYOUT
-------
ซ.ป.
(a)
(b)
-------
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(d)
-------
117 VAC
60 Hz
5 AMP
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[) AC PLUG
-CO- IN-LINE PLUG
BNC
DIRECT WIRING
1
1
1
1
1
1
1
1
1
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-------
3.0 DETAILED SYSTEM DESCRIPTION
3.1 General
A functional description oi: the overall system was given in
Section 2.0, reference should be made to this section for clarification
of the individual subsystem functional requirements. Throughout the
system,, commercially available parts are used where practical. In
some cases it was necessary to modify slightly some of the components.
All call-out parts may be identified by manufacturer and type by
referring to the respective section in the parts list (see appendix).
3.2 Plumbing Subsystem
A detailed diagram of the plumbing subsystem is shown in
Figure 7. In this diagram the functional location of all significant
components are shown, along with the type of tubing, fitting, etc.
A parts layout for the plumbing subsystem is shown in Fig. 8 in
which the relative location of all the components are shown.
In the MEAS mode, gases are pulled through the sample air inlet
line; during the CALIBRATE mode, gases are pulled through the calibrate
air inlet line and through the filter. This latter operation removes
contaminants from the intake air and destroys all of the ozone. Both
the sample and calibrate gases follow common paths after passing point
(7A). Only one of the two ports is open at any given time. After
passing point (8) the incoming gas (200 ml/min) is passed through the
light rejection coil into the detector unit. The light rejection
coil is a single turn of teflon tubingcovered with black-shrinkable
-------
p
\ INLET
CALIBRATION
UNIT
REJEC1
COIl
LEGEND
NEOPRENE
COPPER
TYGON
GLASS
ZZ.~Z.rH~ QUARTZ
o
PARTS CALLOUT
(Stt section 5-3)
-------
Pfcj
TUBE
HOUSING
"LIGHT
REJECTION
COIL
FILTER
COARSE
G SUBSYSTEM
-------
(FRONT PANEL)
PUMP
/
LIGHT
REJECTION
COIL
FIGURE 8. PLUMBING SUBSYSTEM PARTS LAYOUT
-------
vinyl tubing. This device reduces to an acceptable level the amount
of external light entering through the entrance port. The gas passes
over the chemiluminescent disk, through another filter, flowmeter,
valves and pump. A bleed valve (coarse control) is provided to
prevent the pump from being overloaded.
A flowmeter is used for adjustment and monitoring; the meter has
a standard accuracy of + 10% of maximuir. scale from 100% to 10% of scale
reading. The calibration curve is shown in Appendix B; see this section
also for instructions for proper set-up procedure. Two precision
vernier control valves are used for this purpose. The fine flow control
valve is located on the front panel of the instrument.
All parts of the system between the sample inlet port and the
detector are constructed of either glass or teflon in order to prevent
the destruction of ozone. Soft copper and tygon tubing, brass tubing
fittings and brass valves are used where contamination is not a
problem.
Two filters are used in the chemiluminescent ozone meter; these
are shown functionally in Figure 7. Filter A is a disposable milli-
pore aerosol filter which has been modified and includes filter paper,
glass wool, activated charcoal, and manganese dioxide. Its function
is to destroy and prevent ozone contained in the ambient air stream
from entering the ozone generator. This is required to insure o
constant part per. million calibration ozone output from the generator.
Filter B (Figure 7) is a disposable millipore aerosol filter filled
with glass wool. Its only function is to prevent particulate matter
-------
from entering the rotameter and needle valve. A cutaway drawing
of Filter A and instructions for care and maintenance of both filters
are given in Appendix B.
3.3 Detector
A cross sectional view of the detector assembly showing the
principal components is shown in 'Figure 9. The location of the
detector unit in the system is shown functionally in Fig. 1, and
the associated plumbing is shown in Figure 8. The principal components
of the detector are the photomultiplier tube (PM) and HV supply, disk
chamber and associated plumbing. The chamber is designed so that the
inlet air enters the chamber tangentially to the disk and follows
a spiral-like flow over the disk, passing through the exhaust port
which is located in the center.of the disk chamber. A pictoral
representation of this is given in Figure 10. The top of the chamber
consists of a quartz window sealed to the chamber, thus providing an
air-tight chamber.
Light entering the chamber by the inlet port is reduced to an
acceptable value by means of a loop in the inlet glass tubing. The
loop is encased in black vinyl heat-shrinkable tubing. Black rubber
tubing satisfies the requirements for the exit port.
The cutaway view of the PM tube and housing in Fig. 9 shows the
placement of the special grounding braid located between the tube
near the cathode end and the MU-metal shield. The latter shields
against stray electric and magnetic fields. The braid reduces noise
due to static charge buildup on the tube. This is an addition to the
-------
PM TUBJ
PM TUBE
HOUSING
MU-METAL SHIELD
GROUNDING BRAID
INSULATOR
-<"
WINDOW
REMOVABLE PLATE
(DISC HOLDER)
EXHAUST
PORT
(TOP VIEW)
FIGURE 9. DETECTOR ASSEMBLY
GROUNDING
BRAID
MU-METAL
"SHIELD
MOUNTING
i PLATE
PLATE
"OPENING
DISC
PM TUBE
-------
FIGURE 10. AIR FLOW PATTERN IN DISC CHAMBER
-------
standard PM tube housing. The separation distance between the PM tube
cathode and the chemiluminescent disk is approximately 1/2 inch. See
Appendix B.10 for details on tube handling.
The cathode of the PM tube is positioned approximately flush with
the face of the PM tube housing bolt flange. A circuit diagram of the
PM tube base wiring is shown in Figure 11. The tube is an EMI Type
-9
9558C selected for dark current <10 amps. The high voltage (HV) for
the PM tube is generally set for the value which yields a gain = 200 A/L.
A complilation of the PM tube characteristics for several 9558C
type PM tubes is given in Table 1. This includes the factory speci-
fications and the measured values for dark current. The ratio of
measured to rated dark current was approximately 3/1 which was in
line with the expected increase in PM tube dark current due to
increased temperature. The factory rated value is run at 20ฐC while
the units in the laboratory were operated somewhat above this level.
The signal-to-dark current ratio, which was used as a measure
of comparative sensitivity for the PM tubes, was measured on the
same unit, same disk, etc., with no changes in conditions within
practical limits.
The high voltage supply is a Power Designs Model 2K-10 with front
panel controls which allow for precise selection of the high voltage
value. A cover is provided for this unit so that the voltage controls
will not inadvertently be changed. The unit is so designed so that
both the high voltage and primary power ON switches are left in the
ON positions and the power for the entire instrument controlled
-------
NJ
U>
MU-METAL
SHIELD
HV CONNECTOR
- RI;L - 200K, 1% METAL FILM
Dl - ZENER DIODE 1N5276B
Vz = 150 V
V_ = 0.85 mA
T&
ft,,
p 12.
-. OUTPUT
) BNC
-------
TUBE 9558C DARK
SERIAL # CURRENT
(RATED)
11781
11959
11987
11814
11994
11312
20002
20175
2.
0.
1.
3.
0.
2.
2.
0.
6
8
7
0
5
2
8
8
DARK RATIO OF
CURRENT QUOTED TO
(MEASURED) MEASURED
6.8
2.4
4.7
10.0
6.2
0.5
1.5
2
3
2
3
3
0
1
.62
.00
.76
.33
.55
.178
.88
HIGH CATHODE
VOLTAGE (FOR SENS.
GAIN OF 200) yA/L
1930
990
1130
1970
1030
1340
1110
1090
180
94
118
170
110
96
98
111
SIGNAL TO COLOR
DARK CURRENT SENSITIVITY
RATIO B R IR
54.0
100.0
16.0
23.0
180-200
16.7
128.0
10.3
8.2
9.0
7.4
7.0
7.1
8.6
52
26
41
55
36
34
30
30
4.2
0.4
1.6
5.8
1.2
2.6
0.6
0.7
Unit used in Model EU-525-08
-------
by the one power switch. A test was made on 5 HV supplies to
determine the accuracy of the voltage setting controls. This was
done by setting the controls for the 500, 750 and 1000 volt levels
in turn and measuring the true output with a Fluke Model 895A DC
null voltmeter. The results are shown in Table 2.
Table 2
HV POWER SUPPLY SETABILITY TEST
Unit Number
9C2151
902166
902185
902193
902163
500
501.4
501.6
501.94
501.65
501.43
Vcltage Setting
750
751.5
751.9
752.5
751.94
751.71
1000
1001.8
1002.2
1002.985
1002.28
1001.96
A shutter is incorporated in the disk housing between the quartz
window and the cathode of the PM tube. The primary purpose of the
shutter is to facilitate the measurement of the PM tube dark current.
In addition it is used to protect the tube from external light
when the disk is replaced. Access to the disk is through the door
on the front panel. A miniature lab jack is used to raise and
lower the disk holder. An interlock circuit, designed to prevent
inadvertent exposure of the PM tube to excess light, gives visual
indication for the fully open and fully closed conditions for the
shutter. When the shutter is in the fully opened position, a mechan-
ical stop prevents opening of the disk access door. A buzzer sounds
-------
if the disk access door is opened when the shutter is in any but the
fully closed condition. Details on this circuit are given in Figure 12.
3.4 Calibration Unit
In the calibration unit clean air is exposed to a constant
amount of ultraviolet radiation from a low-pressure mercury arc lamp.
o
The particular spectral region of interest is around 1850 A. The
o
resonance line of mercury is 2537 A; however, enough energy is radiated
in the shorter wavelength region to produce the desired ozone level.
The calibration unit consists of a low pressure mercury arc lamp, a
quartz tube through which the clean air flows, and an adjustable
aperature and solenoid controlled shutter. A cutaway drawing of the
calibration unit listing the major components, is shown in Figure 13.
Details on lamp replacement and aperture range adjustments are given
in Appendix B.5 and B.9, respectively. The level of radiance is
controlled and monitored by means of a variac and lamp current meter.
Various, but repeatable, levels of 0- concentration are obtainable
with the adjustable aperture. The specific calibration curve for
the instrument is shown in Figure 14.
The housing is essentially a sealed unit to preclude the
escape of ozone or UV radiation. Because of the thick wall con-
struction, the unit is reasonably stable, thermally. The lamp is
left on at all times and the unit is effectively turned on and off
by activation of the electrically operated shutter. The particular
UV lamp used is rated at 17 mA. The lamps are pre-aged for 400-500
hours and then selected for optimum characteristics.
-------
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GREEN
NOTE: SWITCHES SHOWN WITH SHUTTER OPEN AND DOOR CLOSED
-------
HOUSING, IRRIDITED
2024 ALUMINUM
ALUMINUM
REFLECTOR
ROTARY SOLENOID
SHUTTER
1.75"
VARIABLE
DIA APERTURE
PEN RAY
UV LAMP
MOUNTING PLATE
& LIGHT BAFFLE
QUARTZ TUBE
10 mm OD
FIGURE 13, CALIBRATION UNIT (top view)
-------
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-------
The ozone concentration is dependent on lamp temperature,
lamp current, aperture setting, and flow rate. The lamp temper-
ature is regulated by the thermal stability of the unit. The
result of lamp current variation on the amount of ozone generated
in individual calibration units was determined for a current range
of 5 to 18 mA, with a constant aperture setting of 0 (i.e., maximum
opening) and air flow rates of 150, 200 and 300 ml/min. A typical
plot of this dependency is shown in Figure 15. The dependency of
lamp current as a function of line voltage is shown in Fig. 16
for one flow rate and constant aperture setting. At a flow rate
of 100 ml/min, ozone output deviation is approximately 1.5 percent
per volt change in AC line voltage. These values are typical.
Attenuating the photon flux incident on the quartz tube by
reducing the aperture diameter from 1.0 inch (micrometer set at 0),
to 0.5 inch (micrometer set at 10.0) decreases the ozone output
of the calibration unit, as shown in Figure 14.
The stability of the calibration unit is within the sensitivity
of the monitor and the experimental error of the calibration procedure.
Reproducibility error on the order of 6 percent was evident from the
calibration data, which also is within the determined repeatability
of the experimental procedure.
Ozone concentration generated by the calibration unit at various
air flow rates, source currents and aperture settings was determined
by the Neutral Buffered-Potassium Iodide Method and also by comparison
to a separate calibrated ozone source after the unit in test was
permanently installed in the monitor chassis. The detailed calibration
technique is given in Appendix B.12.
-------
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-------
A calibrated ozone generator identical to the installed unit,
preceded by an ozone-moisture trap and a mass flow meter, was attached
to the sampling port of the ozc*ne monitor being tested (see Fig. 17).
Operating the monitor in the sample mode provided comparison data,
which was indicative of the final calibration for the installed unit
at various aperture settings. The stability and reproducibility
of the individual unit was also observed.
3.5 Timing and Control Unit
The timing and control unit provides selectable timing cycles
for the sample air and calibrate solenoids and the calibrate lamp
shutter. A circuit diagram for the timing and control unit is shown
in Figure 18. There are two automatic modes and three manual modes of
operation which are push button selectable from the front panel of the
instrument. The manual modes are as follows:
CONT MEAS - continuous operation in the measure mode; i.e.,
the sample air solenoid open and the calibration
lamp shutter closed.
CONT CAL - continuous operation in the calibrate mode; i.e.,
the calibrate air solenoid open and the calibrate
lamp shutter open.
CONT PURGE - continuous operation with the calibrate solenoid
open, but with the calibrate shutter closed.
EXT - remote switch for external control of mode.
The two automatic modes of operation are essentially as follows:
SAMP I - 5 min cycle consisting of 75 sec measure, 75 sec
purge, 75 sec calibrate, and 75 sec purge.
SAMP II - operation in the SAMP I mode continuously except
for the 30 min PURGE mode every 12 hours.
-------
CONTROL
117 V ฉ+
-* v._
1 / ) MA METER
XC~X
AMB. AIR
INLET
SCRUBBER
MASS FLOW
METER
CALIBRATED
OZONE
SOURCE
MEAS.
PORT
OZONE
METER
12 v.d.c.
EXHAUST
PORT
ANALOG
RECORDER
FIGURE 17. CALIBRATION UNIT, IN SITU CALIBRATION
-------
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}
EVENT
MARKER
n a 12
NOTE: SYSTEM SHOWW IW
"SAMP. 1 - MEASURE MODE" CONFIGURATION .
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Pi
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17-,
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IBlO INTERLOCK
I@Q CIRCUIT
BUZZER
-------
The indicated mode times for the automatic modes are those initially
set into each unit; these are adjustable and may be set for longer
or shorter periods of time. The timer adjustment procedure is given
in Appendix B.6.
A 12 VDC power supply, located on the main chassis supplies
the voltages for the solenoids, calibrate lamp shutter relays and
indicator lamps.
Event marker connections on the rear panel are connected to
relay contacts which are closed coincident with the actuation of
the calibrate air solenoid and the sample periods for the measure,
calibrate and purge S/H circuits.
The AC voltage supply and buzzer for the PM tube shutter inter-
lock circuit are located on the timer chassis. Details of the inter-
lock circuit are given in Section 3.3.
3.6 Linear Amplifier
3.6.1 Description The amplifier performs the function of
raising the photomultiplier tube anode current from the lowest expected
-9
values, on the order of 10 amps, to the desired 0-1 volt output. A
circuit diagram of the amplifier subsystem is given in Figure 19. The
amplifier is basically a calibrated current meter incorporating a test
position and five linear ranges. In addition, certain other desirable
functions are provided such as an zero offset, span and time constant
control. A summary of the amplifier characteristics is given below:
Sensitivity: Linear - 10~9 amps, FS >
10~8 amps, FS
10~7 amps, FS
10~6 amps, FS
10~5 amps, FS
-------
TOWER SUPPLY
LIWE&O OKHJT
AMPLIFIER
19
MOTE= ALL RESISTORS 1% B1ETAL RLM, EKCEPT
K-l% CAR30M
ปK-GLASS EWCLOSEO
-------
Gain Accuracy - 1%
Input Impedance - 10 ohm
(effective load impedance for PM tube)
Noise - 10 pV p-p, .01 to 1 Hz (time constant-normal)
Output - 0-1 volt, recorder output jack
(5 mA max current)
Drift - Less than 1% after 1 hr warm-up
Time Constant - Normal (see Fig. 21)
1 sec, 2 sec, 4 sec
_Q
Zero Offset - 0 to 10 amps
The input current (PM tube anode current) is passed through a
10 ohm voltage divider. This voltage divider not only provides a
known load resistance but on the two least sensitive ranges it
provides voltage division of 10 or 100 to prevent overload of the
input stages of the amplifier.
The voltage drop across the divider is then sensed by a
varactor bridge operational amplifier. This particular unit, the
-14
Analog Devices 311J, was selected for its low bias current (10 amp),
low bias current drift (10 amp/ฐC) and high input impedance
14
(10 ohm). This amplifier boosts the lower level signals to a
usable level as well as isolating divider from any loading
effects.
The calibration curves for the linear scales are shown in Figure 20.
The signal is fed into the output amplifier through a ten-turn linear
potentiometer, which provides a continuously variable span control.
Capacitors are placed across the feedback resistor in the output
amplifier to provide filtering to reduce high frequency noise and
smooth the output. A four-position switch selects the proper capacitor
-------
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-------
for a time constant of normal, 1, 2, or 4 seconds. The amplifier
band-width for the normal position of the time constant control
is shown in Figure 21.
The effectiveness of the filters were checked by applying
step functions to the input and recording the output either on
a scope with camera or on a strip chart recorder. These are
shown in the scope photographs in Fig. 22 for time constant set-
tings of normal and 1 sec, respectively. The upper trace is the
output response, the input waveform is shown in the lower trace.
The horizontal sweep and vertical gain are identical in each
illustration.
The output is brought out of the amplifier box through two
BNC connectors connected in parallel. The front panel meter is
connected to one and a rear panel recorder output jack is connected
to the other.
Zero offset or base line adjustment is provided by a bucking
voltage fed into the top of the 10 ohm PM tube anode load. This
is controlled by a 10 turn linear potentiometer and is adjusted
for zero offset at zero reading on the dial, and provides linear
8
offset up to 10 amps at a dial setting of 100.
The unit is completely self contained. An Analog Devices
100 mA + 15 volt power supply allows the unit to be operated
directly from 115 VAC. It is enclosed in an aluminum box with
removable side plates and switch shafts long enough to reach through
the front panel.
-------
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IV
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Figure 22- Amplifier 10 Amp Full Scale, Output Sensitivity XI
-------
Standard maintenance and calibration procedures for the amplifier
are given in Appendix B.7.
3.7 Signal Conditioner
The purpose of the signal conditioning unit is to sample
the amplifier output signal from the amplifier at the appropriate
points in time; i.e., in the measure, calibrate and purge modes,
and properly combine these signals in such a way that the resulting
signal is a smoothed continuous value which has been corrected for
base-line and calibration values.
A diagram showing the signal and sampling time-relationship
is presented in Fig. 23, a functional circuit diagram is shown
in Figure 24. The normal time-sampled signal, consisting of 75 sec
calibrate, 75 sec purge, 75 sec measure and 75 sec purge constitute
one complete sampling cycle. Timing signals for the sample and
hold amplifiers are shown as the control inputs - calibrate, purge
and measure, respectively. These control signals initiate the
reset condition in which the s&mple and hold amplifier acquires the
new input signal and then holds this signal at its output until the
next reset signal.
As illustrated in the functional diagram the purge signal is
subtracted from the calibrate and measure signals and the resultant
signals are presented to the inputs of the analog divider as c-p
and m-p, respectively. The subtraction is accomplished in the
differential amplifiers. The output of the analog divider is,
-------
(a)
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-------
(as one would expect it to do due to disk delay) then, for a given
concentration of ozone, the measure signal is automatically corrected.
That is, initially a calibration is made and a given concentration
of ozone produces a certain output signal; as conditions change,
such as the decay of the disk then the output signal is corrected
to produce the same value for a given concentration of ozone.
An output amplifier and filter combination is used to smooth
the discontinuities in the signals due to the discreet time
sampling characteristics of the sample and hold amplifier. The
output is a continuous signal representing the ozone concentration
for a fraction of each 5 min cycle.
The detailed circuit diagram for the signal conditioner unit
is shown in Figure 25. The normal output signal from the ozone
meter; i.e., the cyclic signal shown in Fig. 23(a), is amplified
by the X10 input amplifier and this signal is presented simultan-
eously to all three inputs of the sample and hold (S/H) amplifiers.
The S/H mode control signals are obtained from the timing & control
unit. The output of the S/H amplifier is -10 V for a normal input
to the system of 1.0 V. These S/H signals are presented to the
respective inputs of the two difference amplifiers. Since one of
the constraints of the analog divider network is that |m-p|_<|c-p|
a *10 network was inserted in the output of the m-p difference
amplifier. This accomplishes several things; it satisfies the
constraint up to an effective value of mป10(c) which allows one to
keep the calibration signal at a reasonable level and it cancels
-------
INPUT
AMPLIFIER
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ZERO VOLTS - SAMPLE MODE
+15 VOLTS - HOLD MODE
OUTPUT
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10 Uf
II-
-------
the factor of 10 existing in the analog divider output. The output
amplifier converts to a positive going signal and provides for some
smoothing of the inherent step function response of the S/H amplifiers
during the updating period.
-------
APPENDICES
Appendix
A. INSTALLATION AND OPERATION
A.I Preliminary Set-Up Procedure
A.2 Turn-on Procedure
A. 3 Operational Checks and Adjustments
B. MAINTENANCE, CALIBRATION AND ADJUSTMENT PROCEDURES B-l
B.I Main Chassis Removal B-l
B.2 Disc Replacement B-l
B.3 Flow Rate Adjustment and Check B-2
B.4 Filter Maintenance B-4
B.5 UV Lamp Replacement B-4
B.6 Timer Adjustment B-6
B.7 Amplifier Calibration B-8
B.8 Signal Conditioner Calibration Check B-9
B.9 Calibration Range Change B-9
B.10 PM Tube Replacement B-ll
B.ll Calibration Procedures for the Calibration Unit B-12
B.12 Chemiluminescent Disk Preparation B-17
C. PARTS LIST C-l
C.I Detector Assembly C-2
C.2 Calibration Assembly C-2
C.3 Plumbing Assembly C-3
C.4 Timing Control C-3
C.5 Amplifier Assembly C-4
C.6 Signal Conditioning Unit C-5
C. 7 Chassis and Cabinet C-5
C.8 Interlock Circuit C-6
C.9 AC Power C-6
D. SUBSYSTEM MANUALS D-l
-------
APPENDIX A
INSTALLATION AND OPERATION
r
A.I Preliminary Set-up Procedure
(1) Access to Main Chassis
(a) Remove screws from front panel.
(b) Check for freedom of movement of air inlet lines signal cable,
and power cable at rear of unit, or disconnect as appropriate.
(c) Slide chassis out until it stops.
NOTE: A safety chain restrains the chassis from
extending beyond the first stop. This should
not be removed unless chassis is to be removed
completely from cabinet.
(2) Install Photomultiplier Tube
(a) Install the PM tube in the PM tube housing and mount on
detector unit.
NOTE: Care should be taken not to expose the PM
tube to strong light; excessive exposure
requires approximately 24-48 hours for dark
current to decay to normal value.
(3) Attach the HV and signal coax cables to the PM tube housing.
*
(4) Remove shunt wire from output meter terminals. (This shunt wire
is a precautionary measure taken in shipping to prevent damage).
(5) Visually Inspect unit for any obvious damage.
(6) Slide main chassis back in place.
(7) Install chemiluminescent disc (Appendix B.2).
CAUTION: The instrument is designed for normal
operation with both front and rear panels in
the closed condition. Opening either end will
result in a temperature rise in certain components,
Complete removal of chassis is satisfactory pro-
viding ventilation below chassis is provided.
-------
A. 2 Turn-On Procedure
(1) Close shutter - full closure indicated by AMBER Lamp.
(2) Set SENSITIVITY to 5.
(3) Set SPAN to 0.
(4) Set TIME CONSTANT to 1 sec.
(5) Adjust HV to recommended value for gain of 200 A/L (see specification
sheet).
(6) REPLACE HV Power Supply Cover.
(7) Turn AC POWER switch to ON.
NOTE: Initial operation procedures should include
purging of the air intake lines with high
levels of ozone to destroy contaminants.
A.3 Operational Adjustments/Checks
(1) Adjust LAMP CURRENT to 17.5 mA.
(2) Set FLOW to 200 ml/min. (see spec sheet for proper, flowmeter
settings) (See Section B.3 for
procedure)
(3) Check dark current - note value.
(4) Open shutter - full open indicated by RED Lamp.
(5) Switch to GAL mode - note value.
(6) Switch to desired operating mode.-
(7) Set amplifier controls to desired range and time constant.
-------
APPENDIX B
MAINTENANCE, CALIBRATION AND ADJUSTMENT PROCEDURES
B.1 Main Chassis Removal
(1) Remove screws from front panel.
(2) Slide chassis out a few inches and disconnect the safety chain.
(3) Disconnect HV power supply AC cord and output cable, and fan power
cord.
(4) Slide chassis out until safety catches on chassis slides stop move-
ment. (The weight of the instrument should be supported by the
operator.)
(5) Depress safety catches on slides and remove chassis from cabinet.
NOTE: When operating unit out of cabinet, raise chassis
l"-2" off bench for increased component ventilation.
B.2 Disc Replacement
(1) Move shutter control to CLOSED position. CLOSED indicator light
mus t be on.
(?.) Open disc access door and lower disc holder by turning knob counter-
clockwise until holder stops. Lift holder enough to clear locating
pins and pull unit forward. Be careful not to drag against top
plate of unit.
(3) Replace old disc with new o;.ie making note of elapsed time.
(4) Place holder back in unit using two locating pins on bottom plate
to correctly position holder. Be sure Neoprene outlet hose is not
pinched behind holder, and 0-ring is properly seated.
(5) Turn knob clockwise until holder is firmly seated. If possible, the
system should be checked for leaks each time the disc is changed to
avoid erroneous data.
-------
B.3 Flow Rate Adjustment and Check
(1) The proper flow rate is 200 ml/min.
(2) Adjustment of the air sampling rate is accomplished with the fine
control valve (front panel mounted) and the coarse valve (located
just behind the front panel).
(3) Flow rates at the ambient air sampling port should be checked
periodically, either with a mass flow meter device or with a
rotameter capable of measuring 200 ml/min with an accuracy of + 2%.
It is recommended that where an external flow meter is available
that it be used to make final adjustments to the air flow.
(4) A calibration curve for the flowmeter is shown in Fig. B-l.
-------
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-------
B.4 Filter Maintenance
(1) Filter A (see Fig. B-2) is a millipore aerosol filter which has been
modified and includes filter paper, glass wool, activated charcoal,
and manganese dioxide. The filter is prepared by placing a disk of
Whatman #541 filter paper in the base of the aerosol filter. A
layer of activated charcoal is placed up to the first lip and is
covered by a second disk of filter paper. The remainder of the
aerosol filter is filled with glass wool. Manganese dioxide is
then sprinkled and allowed to sift into the glass wool. The aerosol
filter is reassembled by fitting the second section back into the
first section. To insure that the filter is air tight, cover with
tape or seal the joint using acetone. Under normal monitoring con-
ditions this filter should quantitatively destroy ozone for a period
of at least 12 months; however, replacement at shorter intervals is
recommended when high concentrations of ozone are measured routinely.
(2) Filter B is a disposable millipore aerosol filter filled with glass
wool. The glass wool should be replaced as needed. Visual inspec-
tion at 6 month intervals should suffice.
B.5 UV Lamp Replacement
(1) Turn AC power OFF.
(2) Disconnect lamp from transformer with in-line connector. (CAUTION:
Power must be OFF before disconnecting lamp from transformer.)
(3) Remove top plate.
(4) Loosen Allen set-screw holding UV lamp.
(5) Note position of tip on UV lamp with respect to end wall. Slide
lamp out towards rear of unit, removing shield at same time.
(6) Install new lamp with tip at same position as old lamp, installing
the shield as the lamp is slid into position.
(7) Tighten Allen .set-screw just enough to hold lamp in position, as
excessive tightening could damage the lamp insulator.
(8) Opening in the shield should be in position for maximum light through
aperture.
(9) Install top plate making sure micrometer shaft is in aperature arm
socket and connect in-line power connector.
(10) Turn on AC power.
(11) Calibrate output against known ozone concentration, or use standard
KI technique.
-------
AIR FLOW
FILTER PAPER
ACTIVATED
CHARCOAL
GLASS WOOL
POWDERED WITH
FIGURE B-2. FILTER "A" - CUTAWAY DRAWING
-------
B.6 Timer Adjustment
B. 6.1 Main Timer and Cycle Control
(1) The basic stopping time for the programming switch is
controlled by the small continuous running switch.
The 1 rpm allows for selection of basic stopping times
from 1 sec intervals' to 60 sec intervals.
The unit is presently adjusted for 5 sec intervals.
(2) The 7 channel programming switch is stopped at 5 sec
intervals as indicated in (1). Each function is color
coded as follows:
Red activators - purge mode (25 sectwice per cycle)
White activators - calibrate mode (25 seconce per
cycle)
No activators - measure mode (25 seconce per cycle)
Single blue activator - sample-mode (5 sec) for
respective S/H amplifiers.
Additional channels used for mode control lights and
event marker.
(3) The activation time for the respective modes may be
readily changed by means of adding or deleting the
activators in the respective channels.
-------
B.6.2 Purge Time
(1) The purge timing cam is mounted on a shaft by means of a
heavy duty friction unit which allows for each finger
adjustment of the timing sequence,,
(2) The cam may be set for "on-time" of from 2% to
total overall time cycle.
of the
(3) The cam opening or "on-time" may be adjusted by loosening
the cam screw and turning the movable cam to the required
degree of opening and then re-tightening the screw.
(4) See Fig. B-3 for identification of components.
CAM
ADJUSTMENT.
SCREW
8VNC. MOTOR
OPEN
{COMMON
LINE
WIRING DIAGRAM ONE OB MORE CAMS
FIGURE B-3. TIMER ADJUSTMENT
-------
B.7 Amplifier Calibration
It is not necessary to remove the amplifier from the unit
for this calibration. Simply disconnect the input and attach a volt-
meter to the output.
Equipment needed - 10 mV and 10 V source
- Voltmeter - HP-425, or equivalent
- Oscilloscope - Tektronix 547, or equivalent.
All adjustments are located on top of the unit and labeled.
(1) Turn the unit on and allow 30 min for amplifier to stabilize. _
Leave the input disconnected. Then, turn the sensitivity to 10 ,
F.S. output to XI and time constant to NORM. Adjust Rl for zero
output.
5 _Q
(2) Turn the sensitivity control alternately between 10 and 10
while adjusting Rl for a minimum change in output between switch
settings.
(3) Set the sensitivity control at 10 and adjust R2 for zero output.
Amplifier Disassembly - To remove the amplifier from the
unit, remove the three knobs and three screws from the
front panel. Next disconnect the three BNC connectors
from the top of the amplifier and unplug the power cord.
The back of the amplifier can now be raised and the unit
pulled out over the timing chassis.
-------
B. 8 Signal Conditioner Calibration Check
(1) Disconnect input to signal conditioner and reconnect a 1.0 V dc
signal.
(2) Disable timer by removing AC power. Rotate timer to desired
position manually.
(3) Measure with DVM the voltage at each sample and hold output;
should be 10.0 V + 1%.
(4) Check the * 10 at the output of the upper difference amplifier.
(5) Under normal operating conditions, read the respective S/H
signals and calculate the (m-p)/(c-p) ratio. Measure the output
signal and compare to calculated value.
B.9 Calibration Range Change
(1) Turn AC power off.
(2) Disconnect safety chain from rear of chassis and pull chassis
forward until calibration unit is completely exposed.
(3) Remove top plate.
(4) See Fig. B-4 for following steps:
a. To adjust for lower calibration range, set micrometer at 10,
loosen the two 4-40 retaining screws and rotate aperture cover
counter-clockwise until minimum aperture opening is obtained.
b. To adjust for higher calibration range, set micrometer at 0,
loosen the two 4-40 retaining screws and rotate aperture cover
clockwise until maximum aperture opening is obtained.
(5) Tighten the aperture cover retaining screws and install top plate,
making sure micrometer shaft is in aperture arm socket.
(6) Calibrate output against known ozone concentration, or use standard
KI technique.
-------
ALUMINUM
REFLECTOR
\
PEN RAY
UV LAMP
VARIABLE DIA.
APERTURE
MICROMETER
tunas
Retaining
Screws
QUARTZ TUBE
Aperture Adjustment Range
Small: .047" to 0.5" dia.
Large: .5" to .984" dia.
FIGURE B-4. CALIBRATION UNIT (side view)
-------
B.10 Replacement of PM Tube
(1) Turn off AC power.
(2) Remove screws from front panel and slide the chassis out until it
stopso
(3) Disconnect the HV power supply and signal cables from the top of the
PM tube housing.
! CAUTION - When handling PM tubes, avoid exposing the tube '
' to light. This will insure a normal dark current :
| level for the tube. If exposed, allow 24-48 hours :
j for return to normal level. :
(4) Remove three 8-32 screws from the PM housing flange and lift the
complete housing assembly off the detector unit,,
(5) Remove three 6-32 screws from the top of the housing (evenly spread
on outside rim) and remove the outer housing.
(6) Remove the Mu-metal shield from the PM tube and then unplug the
PM tube.
(7) Install the new tube9 reversing the above procedure, being careful
not to dislodge the metal grounding braid near the end of the
Mu-metal shield nearest the cathode at the PM tube.
NOTE; Light leaks will show up as excessive dark current.
Care should be exercised in assemblying the housing.
(a) It may be necessary in some case to use black
tape to seal the joints of the housing around the
BNC plug end,
(b) An 0-ring in the mounting flange of the tube
provides an adequate light-tight seal for the open end
of the housing.
(c) A check should be made around the PM tube shutter
to determine the susceptibility to light leakage,
-------
B-ll Calibration Procedures for the Calibration Unit
Apparatus - The unit in test was placed in line with an ozone-
moisture trap of Drierite and No. 40 mesh charcoal, a mass flowmeter,
two 25 ml graduated all glass inpingers (open end nozzle type) , an air
flow control valve and air pump (refer to Fig.B-5). Quartz tube to
impinger connection was accomplished by means of a teflon reducing
union, glass tubing and aground glass joint, slightly lubricated with
Kel-F No. 90 stopcock grease. A 12 VDC power supply was used to
activate the internal shutter and the UV lamp current was adjusted by
means of an autotransformer and a Pen Ray 10 mA transformer. All
tests were timed with an electronic timer and AC power was regulated
at 117 volts.
Air flow was metered with a Hastings mass flowmeter (a ther-
moelectric type sensor) with a range of 0 to 300 standard ml/min,
readable to 1.5 ml/min and stable within 2% to 250psia.
(2) Reagents - The absorbing reagent was prepared with reagent
grade chemicals - 13.61g potassium dihydrogen phosphate, 14. 2g of
anhydrous disodium hydrogen phosphate and 10. Og of potassium iodide,
diluted to 1.0 liter with distilled water which had been passed through
two ion exchange columns and a millipore filter. Prior to initial use,
each new batch of absorbing reagent was aged for 24 hrs. in the dark
and at room temperature.
Standard iodine solution, 0..05N, was prepared by carefully
weighing 16. Og of potassium iodide and 3.173g of iodine and diluted
to exactly 0.5 liter.
-------
(3) Procedure - Exactly 10 ml of the absorbing reagent was
pipetted into each of two tandem impingers, carefully shielding the
solution from light whenever possible.
Ambient air was aspirated through the assembled train for
sampling periods of 15 to 30 minutes, at flow rates between 50 to
300 ml/min. Immediately following sampling, the exposed absorbing
solution was transferred first to a graduated cylinder, then to a
1 inch diameter colorimeter cuvette. At the lower flow rates (i.e.,
less than 300 ml/min)9 no appreciable evaporation was observed in
either impinger.
(4) Analysis - Absorbance was determined within 10 to 15 minutes
after sampling, with a Bausch and Lomb Spectronic 20 Spectrophoto-
meter, at 352 nm and with unexposed absorbing reagent as the
reference.
Standardization was checked each day during the test, with
an 0.0025N iodine standard solution prepared by pipetting 5 ml of the
0.05N standard stock solution into a volumetric flask and diluting
to 100 ml with absorbing reagent. A series of 0.2, 0.4, 0.6, and 0.9 ml
portions of the diluted standard iodine were pipetted into volumetric
flasks and diluted to 25 ml with absorbing reagent and the absorbance
of this known series was determined at 352 nm.
-------
Calculations - Absorbance and calculated normality of the
standard iodine solution was plotted (refer to Fig.B-6), and the
standardization factor, M, was determined from the normality of the
standard solution at absorbance 1.0.
03 (ppm) = Sample absorbance x M/V (Ref. A-l)
where; M (standardizations factor) = 1.224 x 10 I
I = Intercept at absorbance 1.0 and
V = Volume of sample in liters
The above calculations were executed, assuming no deviation
from the standard conditions o:_ 760 mm of mercury and 25ฐ c, and the
air sample volume was used directly as recorded.
Then: Volume = 24,47 liters
ly ! = 24.47 yl 03 and
10 ml IN iodine = 5 x 103 ymole I2 = 1.224 x 10 yl 03
Procedure efficiency - Varying the sampling time, not
exceeding a maximum of 30 minutes or a minimum of 15 minutes and
obtaining the absorbance reading at intervals of 10 to 15 minutes
after sampling, the error observed between consecutive samples was
negligible. Variations did occur among successive batches of absorbing
reagent, which gave only 93% reproducibility.
Ref. B-l Saltzman, B, E., Determination of Oxidants (including Ozone):
Neutral Buffered-Potassium Iodide Method, Public Health Service
Publication No. 999-AP-ll.
-------
A.C. VOLTAGI
REGULATOR
^
LAMP CONTROL
AMB. AIR
INLET
SCRUBBER
V
'
t
MASS FLOW
METER
A.C.
VOLTMETER
12 v.d.c.
SUPPLY
!SHUTTER
CONTROL
APERTURE
ADJ.
CALIBRATION
UNIT
LAMP
SUPPLY
MA
METER
IMPINGERS
j SPECTROMETER i
TIMER
(ELECTRONIC
COUNTER)
-------
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-------
B-12. Chemiluminescent Disk Preparation
The chemiluminescent disks are prepared by absorbing an
organic dye, Rhodamine B on a finely divided silicon-gel surface
which has been made moisture-insensitive by treatment with a hydrophobic
agent. The high surface area material used as the substrate was
Eastman thin layer chromatographic-grade silica-gel sheet, Type
ECS-6061. The dye compound was Rhodarodne-B.O (the hydrochloride
salt form), and the hydrophobic coating material was General Electric
silicone resin, type Sr-82.
The recommended procedure for preparation of the chemiluminescent
disk surface is as follows:
1. Cut 2 inch diameter disks from a silica-gel sheet and dry
in an oven for 1 hour at 110 to 120ฐC.
2. Prepare a 10% (W/W) solution by diluting Sr-82 (60% resin)
1:6 with benzene. Immediately after drying, dip the disk in the
hydrophobic resin solution for 1 minute. Remove from the solution
and drain off the excess. Place disks into oven and dry for 2A-48
hours at 110-120ฐC.
3. After removing dried disk from oven, immediately dip the disk
for 1 minute in a solution containing 0.1 gram per liter of Rhodamine-
BS0 in acetone. Drai.n off the excess solution and return disk to
oven for about 5 minutes to evaporate off the remaining acetone. Disks
prepared in this way are insensitive to moisture but should be protected
from the atmosphere, and bright light since the dye compound may
undergo slow oxidation. The best practice is to store them in a
desiccator.
Hodgeson, J. A, Krost, K. J., O'Keeffe, A. E, and Stevens, R. K.,
"Chemiluminescent Measurements of Atmospheric Ozone," Anal. Chem.,
-------
APPENDIX C
PARTS LIST
A parts list for each of the major sub-assemblies is given in this
appendix. The non-standard parts are indicated by an RTI drawing number.
All other components are identified by manufacture and manufacturers'
part number. Most of the parts listed are self-explanatory.
The high voltage power supply (Power Design, Model 2K-10) , the Hh
15 Vdc supply (HP Model 60155C) , and the 12 Vdc supply (Deltron Model
C12-2.8) are not included since they are fully described by their res-
pective instruction manuals, which are included in the sub-systems
manuals.
-------
C.I Detector Assembly
Part No. Description
001 Housing
010 PMT Housing
020 Photomultiplier
030 High Voltage Power
Supply
040 Quartz Window
(2% in. diam. x
1/16 in. thick)
050 Jack
Manuf act lifer
RTI
Pacific Photometric
EMI
Power Designs Inc.
Mfg. Part No.
Dwg. No. 001
62 (modified
length)
9558C
2K-10
Thermal American Vitreosil
Fuzed Quartz Company
Precision Scientific Little Jack
Co.
C.2 Calibration Assembly
Part No. Description
100 Housing
120 UV Lamp
130 Lamp Power Supply
140 Auto-transformer
141 Knob
150 Milliammeter
160 Shutter Solenoid
170 Iris Diaphragm
180 Micrometer Control
190 Quartz tube
(standard normal wall
10.2mm o.d. x 8" L)
Manufacturer
RTI
Pen-Ray
Pen-Ray
Staco
Raytheon
Triplett
Ledex
Edmund Scientific
Starrett
Thermal-American
Fuzed Quartz Company
Mfg. Part No.
Dwg. No. 100
11SC-1B
SCT-3
121
70-4-26
430
H-1079-032
681
440-3RL
Spectrosil
-------
C.3 Plumbing Assembly
Part No.
1
2
3
4
5
6
7
8
9
10
11
12
C.4
Part No.
900
T-l
TP-1
T-2
5901
Kl
K2
K3
Bl
B2
PWR1
Description
Bulkhead Adapter
Male Elbow
All Tube Tee
Valve, fine
metering
Valve, fine
metering
Male Connector
Tie connector,
teflon
Reducing Union
Solenoid Valve
Flow Meter
Elbow (Teflon)
Pump
Timing Control
Description
Chassis
Cycle Timer
Cycle Programmer
Purge Timer
Mode Switch
Valve Relay
Valve Relay
Timer Relay
Lamps (Mode Switch)
Lamps (Shutter & Power)
+ 12 VDC Power Supply
Manufacturer
Swage lok
Swag el ok
Swag el ok
Nupro
Nupro
Swagelok
Chemplast
Chemplast
Valcor Engineering
Brooks Instrument
Division
Chemplast
Neptune Products, Inc.
Manufacturer
Bud Radio
Sealectroswitch
Corp.
11
Industrial Time
Corp.
Switch craft
Potter & Brumfield
Potter & Brumfield
Potter & Brumfield
GE
GE
Deltron
Mfg. Part No.
400-A1-4
400-2-2
40-3
B-4MA
B-4M
400-1-4
T-T0404-F
T-S0604-F
51C70HT34-6A
1555-OOC1A
T-L0404-F
4K
Mfg. Part No.
AC- 40 3
092-0166-500
092-0765-501
CM-10/10A24
37061/H83P/83P
KA11DG
KA11DG
KA11DG
330
328
C12-2.8
-------
C.5 Amplifier Assembly
Part No.
500
Rl
R2
R7
R8
R9
RIO
Rll
R12
R13
R14
R20 & 21
R22
R23 & 24
R25 & 26
R27
R28
R29
R27
R30
R31
R32
Cl
C2
C3
S501
S502
Al
A2
Ml
PWR1
Description
Chassis
100K Potentiometer
50K "
10K Potentiometer
10K
9 meg 1% Carbon
900K 1% Metal Film
100K " " "
IK "
99K "
qv- a ii ii
Manufacturer
RTI
Helipot
Helipot
Bourns
Bourns
IRC
IRC
IRC
IRC
IRC
IRC
[Trim resistors furnished with AD 183K
10K 10-Turn Pot.
1 meg "
200K " "
1000 Meg ohm
10K Trimpot
10K Potentiometer 10T
100 ohms 1% Metal Film
15K
13K
IK Potentiometer
0.9 yf
1.9 yf
4.1 yf
Sensitivity Switch
Time Constant Switch
Operational Amp.
Operational Amp.
Output meter
Knobs
Power Supply
Bourns
Bourns
Bourns
Victoreen
Beckman
Bourns
IRC
ii
ii
Helipot
Sprague
Sprague
Sprague
Centralab
Centralab
Analog Devices
Analog Devices
Simpson
Raytheon
Analog Devices
Mfg. Part No.
Dwg. No. 500
76PR 100K
76PR50K
3600S
300 7P
amplifiers]
3600S
76PR10K
3600S
76PR1K
151D-904X9020W2
15 ID- 19 5X90 35X2
151D-415X9020X2
P-505/(3)PS-21
P-503/(1)PS-21
311K
184J
1150
50-4-1G
AD902
-------
C.6
Part No.
500
S/H1.2&3
Al, 2&3
PWR3
Rl , 2 , 4 , 5
6,7,8&9
R3.10&11
C1,C2,C3
C4
M/D1
C.7
Part No.
701
800
801
802
803
804
805
806
401
301
Signal Conditioning Unit
Description
Chassis
Sample & Hold
Amplifier
Operational Amplifier
+ 15 V Power Supply
10 K Metal Film, 1%
1/4 W
100 K Metal Film, 1%
1/4 W
1 yf, 100V, 1%
.10 nf
Multiplier-Divider
Chassis and Cabinet
Description
Chassis
Cabinet
Front Panel
Rear Panel
Rear Door
Handles
Chassis Slides
Fan
Solenoid Valve Bracket
Clean-up Tower
Parts List
Manufacturer
RTI
Burr Brown
Analog Devices
Hewlett-Packard
IRC
IRC
Electronic Associate's,
Inc.
Sprague
Burr"Brown
Manufacturer
RTI
Optima
Optima
Optima
Optima
Optima
Chassis-Trak
Rotron Mfg. Co.
RTI
RTI
Mfg. Part No.
Dwg. No. 500
BB4013/25
AD183J
60155C
113D-106C701500
BB4030/25
200
Bracket
Pump Mounting
Bracket
RTI
Mfg. Part No.
Dwg. No. 700
E-171920H
P-14
P-7
D-10
H-14
C-230-S-18
Muffin Fan
Dwgk No. 400
Dwg. No. 300
Dwg. No. 200
-------
C. 8 Interlock Circuit
Part No. Description
TR1 Transformer
(12.6 VAC)
S101 Full Open Switch
S102 Full Closed Switch
S103 Door Open Switch
BZ1 Buzzer
B101 Full Open Lamp
B102 Full Closed Lamp
'Manufacturer
Chicago-Stancor
Robertshaw
Robertshaw
Robertshaw
Potter & Brumfield
Dialco/GE
Dialco/GE
Mfg. Part No.
P8130
1MD1-1A
1MD1-1A
1MD1-1A
12VDC
182-8430/327
182-8430/327
C.9 AC Power
Part No.
SI
Fl
PS1
Description
Power Switch
Fuse
Power Strip
Manufacturer
Arrow Hart
Littlefuse
CBC Electronics
Part No.
81024GB
3AG-10AMP
MO-G-D
-------
APPENDIX D
SUBSYSTEM MANUALS
The manufacturer-supplied manuals or data sheets on certain major
components are included in a separate binder. Reference should be made
to these as required for operation, maintenance and repair information.
The manuals/data sheets included are as follows:
I. DETECTOR UNIT
A. Photomultiplier (EMI 9558C)
B. HV Power Supply (Power Designs 2K-10)
II. AMPLIFIER AND SIGNAL CONDITIONER
A. Operational Amplifier (AD 183J) or (AD 184J)
B. Operational Amplifier (AD 311)
C. Sample/Hold Modules (BB 4034/25)
D. Multiplier/Divider Modules (BB 4030/25)
E. Operational Amplifier Power Supply (AD 902)
F. DC Power Supply (HP 60155C)
III. TIMING AND CONTROL
A. Programming Switch (Sealectrowsitch SSC-3A)
B. Programming Switch (Sealectroswitch SSC 11)
C. DC Power Supply (Deltron C-12-2.8)
IV. CALIBRATION VMT
A. UV Lamp (Pen-Ray 11SC-1C)
B. Lamp Power Supply (Pen-Ray SCT-1)
C. Lamp Control (Staco 100 BV)
V. PLUMBING ASSEMBLY
A. Teflon Fittings (CHEMPLAST)
B. Metering Valves (Nupro B4MA)
C. Valve Vernier (Nupro)
D. Pump (Neptune 4K)
E. Rotameter (Brooks 1550)
F. Drying Tower (Drierite)
G. Solenoid Valve (Valcor)
VI. CHASSIS AND CABINET ASSEMBLY
A. Exhaust Fan (Rotron Mark 4)
-------
APPENDIX E
ENGINEERING DRAWINGS
A complete set of engineering drawings for the machine shop
fabricated parts is included in a separate manual. A listing of the
specific drawing sets are given below.
Detector Assembly
Calibration Assembly
Pump Mount
Valve Bracket
Tower Mount
Amplifier Chassis
Main Chassis
Panels
Drawing Set
Drawing Set
Drawing Set
Drawing Set
Drawing Set
Drawing Set
Drawing Set
Drawing Set
# 001
# 100
# 200
# 400
# 300
# 500
// 700
# 600
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