Teledyne BDS-3960 User Manual

Oxygen Analyzer

OPERATING INSTRUCTIONS FOR

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Oxygen Analyzer

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P/N M71903

9/04/02

ECO # 02-232

DANGER

Tox ic g a se s a nd o r fla mma ble liq uids ma y be pr es e nt in this mon itor ing s y stem.

Personal protective equipment may be required when servicing this instrument.

Hazardous voltages exist on certain components internally which may persist
for a time even after the power is turned off and disconnected.

Only authorized personnel should conduct maintenance and/or servicing.
Before conducting any maintenance or servicing, consult with authorized
supervisor/manager.

Teledyne Analytical Instruments i

BDS 3960

Copyright © 2002 Teledyne Analytical Instruments

All Rights Reserved. No part of this manual may be reproduced, transmitted, transcribed,
stored in a retrieval system, or translated into any other language or computer language in
whole or in part, in any form or by any means, whether it be electronic, mechanical,
magnetic, optical, manual, or otherwise, without the prior written consent of Teledyne
Analytical Instruments, 16830 Chestnut Street, City of Industry, CA 91749-1580.

Warranty

This equipment is sold subject to the mutual agreement that it is warranted by us free from
defects of material and of construction, and that our liability shall be limited to replacing or
repairing at our factory (without charge, except for transportation), or at customer plant at
our option, any material or construction in which defects become apparent within one year
from the date of shipment, except in cases where quotations or acknowledgements provide
for a shorter period. Components manufactured by others bear the warranty of their
manufacturer. This warranty does not cover defects caused by wear, accident, misuse,
neglect or repairs other than those performed by Teledyne or an authorized service center.
We assume no liability for direct or indirect damages of any kind and the purchaser by the
acceptance of the equipment will assume all liability for any damage which may result from
its use or misuse.

We reserve the right to employ any suitable material in the manufacture of our apparatus,
and to make any alterations in the dimensions, shape or weight of any parts, in so far as
such alterations do not adversely affect our warranty.

Important Notice

T hi s in str ument p ro v id es measur ement read in g s to it s user, an d serv es as a to o l b y w h i c h
v al uabl e d at a can b e g at h er ed . The i n fo rmat i on p r ov id ed by t h e in st r umen t may assi st th e user
i n el imi nati n g po ten ti al hazard s cau sed b y his p r ocess; ho wev er , it is essent ial t hat all
p er so nn el in v ol ved in th e u se o f t he in st ru men t or it s int er f ace, wi th t h e pr ocess b ein g
measu red , be pr op er l y tr ain ed i n t he pr ocess i tself , as well as all in s t r u m e n t a t io n rel at ed to i t .

The safety of personnel is ultimately the responsibility of those who control process
conditions. While this instrument may be able to provide early warning of imminent
danger, it has no control over process conditions, and it can be misused. In particular, any
alarm or control systems installed must be tested and understood, both as to how they
operate and as to how they can be defeated. Any safeguards required such as locks, labels,
or redundancy, must be provided by the user or specifically requested of Teledyne at the
time the order is placed.

Therefore, the purchaser must be aware of the hazardous process conditions. The purchaser
is responsible for the training of personnel, for providing hazard warning methods and
instrumentation per the appropriate standards, and for ensuring that hazard warning devices
and instrumentation are maintained and operated properly.

Teledyne Analytical Instruments, the manufacturer of this instrument, cannot accept
responsibility for conditions beyond its knowledge and control. No statement expressed or
implied by this document or any information disseminated by the manufacturer or its
agents, is to be construed as a warranty of adequate safety control under the user’s process
conditions.

Teledyne Analytical Instruments ii

Oxygen Analyzer

Specific Model Information

The instrument for which this manual was supplied may
incorporate one or more options not supplied in the standard instrument.
Commonly available options are listed below, with check boxes. Any
that are incorporated in the instrument for which this manual is supplied
are indicated by a check mark in the box.

Instrument Serial Number: _______________________

Options Included in the Instrument with the Above Serial Number:

• 220 VAC: Instrument configured 200-240 VAC, 50/60Hz

power

Teledyne Analytical Instruments iii

BDS 3960

Safety Messages

Your safety and the safety of others is very important. We have
provided many important safety messages in this manual. Please read
these messages carefully.

A safety message alerts you to potential hazards that could hurt you
or others. Each safety message is associated with a safety alert symbol.
These symbols are found in the manual and inside the instrument. The
definition of these symbols is described below:

GENERAL WARNING/CAUTION: Refer to the
instructions for details on the specific danger. These cautions
warn of specific procedures which if not followed could cause
bodily Injury and/or damage the instrument.

CAUTION: HOT SURFACE WARNING: This warning is
specific to heated components within the instrument. Failure
to heed the warning could result in serious burns to skin and
underlying tissue.

WARNING: ELECTRICAL SHOCK HAZARD: Dangerous
voltages appear within this instrument. This warning is
specific to an electrical hazard existing at or nearby the
component or procedure under discussion. Failure to heed this
warning could result in injury and/or death from
electrocution.

Technician Symbol: All operations marked with this symbol
are to be performed by qualified maintenance personnel only.

No

Symbol

CAUTION: THE ANALYZER SHOULD ONLY BE USED FOR THE

NOTE: Additional information and comments regarding a
specific component or procedure are highlighted in the form
of a note.

PURPOSE AND IN THE MANNER DESCRIBED IN
THIS MANUAL.

Teledyne Analytical Instruments iv

Oxygen Analyzer

IF YOU USE THE ANALYZER IN A MANNER OTHER
THAN THAT FOR WHICH IT WAS INTENDED,
UNPREDICTABLE BEHAVIOR COULD RESULT
POSSIBLY ACCOMPANIED WITH HAZARDOUS
CONSEQUENCES.

This manual provides information designed to guide you through
the installation, calibration and operation of your new analyzer. Please
read this manual and keep it available.

Occasionally, some instruments are customized for a particular
application or features and/or options added per customer requests.
Please check the front of this manual for any additional information in
the form of an Addendum which discusses specific information,
procedures, cautions and warnings that may be peculiar to your
instrument.

Manuals do get lost. Additional manuals can be obtained from
Teledyne at the address given in the Appendix. Some of our manuals are
available in electronic form via the internet. Please visit our website at:
www.teledyne-ai.com.

Teledyne Analytical Instruments v

BDS 3960

Table of Contents

Safety Messages ..........................................................................iv

Table of Contents ......................................................................... vi

List of Figures............................................................................... ix

List of Tables ................................................................................ xi

Introduction .................................................................................13

1.1 Overview 13

1.2 Typical Applications 13

1.3 Main Features of the Analyzer 13

1.4 Front Panel (Operator Interface) 14

1.5 Rear Panel (Equipment Interface) 16

Operational Theory .....................................................................18

2.1 Introduction 18

2.2 BDS Sensor 18

2.2.1 Principles of Operation 18

2.2.2 Gas Flow Rate 21

2.2.3 Gas Pressure 22

2.2.4 Temperature effect 22

2.2.5 Recovery from High Level Oxygen Exposure 22

2.2.6 Background Gas Compatibility 23

2.2.7 Stability 24

2.2.8 Maintenance 24

2.3 Sample System 25

2.4 Electronics and Signal Processing 26

Installation ................................................................................... 30

3.1 Unpacking the Analyzer 30

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Oxygen Analyzer

3.2 Mounting the Analyzer 30

3.3 Rear Panel Connections 32

3.3.1 Gas Connections 32

3.3.2 Electrical Connections 33

3.3.2.1 Primary Input Power 34

3.3.2.2 50-Pin Equipment Interface Connector 34

3.4 Electrolyte Refill of BDS Sensor 39

3.5 Testing the System 40

3.6 Powering Up the System 41

Operation ..................................................................................... 42

4.1 Introduction 42

4.2 The Analyzer application 43

4.3 The System Screen 44

4.3.1 Communication Information and Calibration Parameters 44

4.3.2 Setting Software Parameters: Filter, Gas Factor,
Tmp. Coeff. 45

4.3.2.1 The Digital Filter 46

4.3.2.2 The Gas Factor 46

4.3.2.3 Temperature Coefficient 47

4.3.2.4 Set Defaults 48

4.4 Calibration of the Analyzer 49

4.4.1 Zero Cal 49

4.4.1.1 Zero Failure 50

4.4.2 Span Cal 50

4.4.2.1 Span Failure 51

4.5 The Alarms Function 51

4.6 The Range Function 53

4.6.1 Setting the Analog Output Ranges 53

4.6.2 Fixed Range Analysis 55

4.8 Signal Output 55

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BDS 3960

4.9 Switching The Program Back To The Front 56

Maintenance................................................................................. 58

5.1 Routine Maintenance 58

5.2 Adding Water to the BDS Sensor 58

5.3 Fuse Replacement 59

5.4 Battery Backup Replacement 60

5.5 Reinstalling Application software to PPC. 61

5.5 Major Internal Components 62

5.6 Cleaning 62

5.7 Troubleshooting 62

Appendix...................................................................................... 66

A-1 Specifications 66

A-2 Recommended 2-Year Spare Parts List 68

A-3 Drawing List 69

A-4 19-inch Relay Rack Panel Mount 69

A-5 Application notes 70

Material Safety Data Sheet 71

Index............................................................................................. 74

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Oxygen Analyzer

List of Figures

Figure 1-1: BDS-3960 Front Panel ................................................ 15

Figure 1-2: Model BDS 3960 Rear Panel ...................................... 17

Figure 2.1: Cross Section of the BDS Oxygen Sensor ................. 20

Figure 2.2: BDS sensor output at different gas flow rate ............... 21

Figure 2-3: A simplified BDS Sample System ............................... 22

Figure 2.4 Typical Purge-down Curve After Air Saturation............ 23

Figure 2.5: Adding DI Water to the BDS Sensor ..........................24

Figure 2-6: Flow Diagram.............................................................. 26

Figure 2-7: BDS 3960 Electronics Block Diagram ......................... 28

Figure 3-1: Model BDS 3960 Front Panel ..................................... 31

Figure 3-2: Required Assembly Drawer Clearance ....................... 31

Figure 3-3: Rear Panel of the Model BDS 3960 ........................... 32

Figure 3-4: Equipment Interface Connector Pin Arrangement....... 34

Figure 3-5: Adding Electrolyte to the BDS Sensor....................... 40

Figure 4-1: Main Menu .................................................................. 43

Figure 4.2: Parameter Selection Box............................................. 46

Figure 4.3: Range Options List Box............................................... 54

Figure 4.4: Range Setup Screen ................................................... 54

Figure 5.1 Adding Water into the BDS sensor............................... 59

Figure 5-2: Removing Fuse Block from Housing ........................... 60

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BDS 3960

Figure 5-3: Vacuum Degassing for the BDS Oxygen Sensor....... 64

Figure A-1: Single 19" Rack Mount (dimensions in mm) ............... 69

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Oxygen Analyzer

List of Tables

Table 3-1: Analog Output Connections .........................................35

Table 3-2: Alarm Relay Contact Pins ............................................36

Table 3-3: Remote Calibration Connections.................................. 37

Table 3-4: Range ID Relay Connections ....................................... 39

Table 4-1: Gas Factor for Selected Gases .................................... 46

Table 4-2: Parameter Default Values ............................................ 48

Table 4-2: Linear Output for a 0-100 ppm O2 Range ................... 55

Table 4-3: Range ID Output .......................................................... 56

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BDS 3960

DANGER

COMBUSTIBLE GAS USAGE

WARNING

This is a general purpose instrument designed for usage in a
nonhazardous area. It is the customer's responsibility to
ensure safety especially when combustible gases are being
analyzed since the potential of gas leaks always exist.

The customer should ensure that the principles of operating
of this equipment is well understood by the user. Misuse of
this product in any manner, tampering with its components,
or unauthorized substitution of any component may
adversely affect the safety of this instrument.

Since the use of this instrument is beyond the control of
Teledyne, no responsibility by Teledyne, its affiliates, and
agents for damage or injury from misuse or neglect of this
equipment is implied or assumed.

Teledyne Analytical Instruments xii

Oxygen Analyzer Introduction

Introduction

1.1 Overview

The Teledyne Analytical Instruments Model BDS 3960 Oxygen
Analyzer is a versatile instrument for detecting oxygen at the parts-per­billion (ppb) level in a variety of gases. This manual covers the Model
BDS 3960 General Purpose flush-panel and/or rack-mount units only.
These units are for indoor use in a non-hazardous environment.

1.2 Typical Applications

A few typical applications of the Model BDS 3960 are:

• Monitoring inert gas blanketing

• Air separation and liquefaction

• Chemical reaction monitoring

• Semiconductor manufacturing

• Petrochemical process control

• Quality assurance

• Gas analysis certification.

1.3 Main Features of the Analyzer

The Model BDS 3960 Oxygen Analyzer is sophisticated yet simple
to use. The main features of the analyzer include:

• Pocket PC with Windows CE operating system used as a

controller for analyzer functions.

• High resolution, accurate readings of oxygen content from

low ppb levels through 100 ppm. Large, bright, meter
readout.

• New BDS Sensing technology, patent pending.

• Versatile analysis over a wide range of applications.

• Microprocessor based electronics: 8-bit CMOS

microprocessor with 32 kB RAM and 8 kB ROM for I/O
operations.

Teledyne Analytical Instruments 13

Introduction BDS 3960

• Three user definable output ranges (from 0-100 ppb through

0-100 ppm) allow best match to users process and
equipment, plus a fixed 100 ppm over range.

• Auto Ranging allows analyzer to automatically select the

proper preset range for a given measurement. Manual
override allows the user to lock on to a specific range of
interest.

• Two adjustable concentration alarms and a system failure

alarm.

• Two way RFI protection.

• Four analog outputs: two for measurement (0–1 VDC and

Isolated 4–20 mA DC) and two for range identification.

• Convenient and versatile, steel, flush-panel or rack-

mountable case with slide-out electronics drawer.

1.4 Front Panel (Operator Interface)

The standard BDS 3960 is housed in a rugged metal case with all
controls and displays accessible from the front panel. See Figure 1-1.
The front panel has the pocket PC, a digital meter, an alphanumeric
display, and a window for viewing the sample flowmeter.

There are no keys to press on the front panel. All interface with
the analyzer is done through the touchscreen of the pocket PC. The main
functions on the touchscreen are listed below.

• System Perform system-related tasks
(described in detail in chapter 4,
Operation.).

• Span Span calibrate the analyzer.

• Zero Zero calibrate the analyzer.

• Alarms Set the alarm setpoints and
attributes for Alarm 1 and Alarm 2.

• Range Set up the 3 user definable ranges
for the instrument.

• Quit Quit analyzer application.

Teledyne Analytical Instruments 14

Oxygen Analyzer Introduction

Figure 1-1: BDS-3960 Front Panel

Digital Meter Display: The meter display is a Light Emitting Diode
(LED) device that produces large, bright, 7-segment numbers that are
legible in any lighting. It produces a continuous readout from 0-999.9
ppb and then switches to a continuous ppm readout from 0-100.00 ppm.
It is accurate across all analysis ranges without the discontinuity inherent
in analog range switching.

Flowmeter: Monitors the flow of gas past the sensor. Readout is 0.1 to

2.0 standard liters per minute (SLPM) of nitrogen

CAUTION: THE POWER CABLE MUST BE UNPLUGGED TO

FULLY DISCONNECT POWER FROM THE
INSTRUMENT. WHEN CHASSIS IS EXPOSED OR
WHEN ACCESS DOOR IS OPEN AND POWER
CABLE IS CONNECTED, USE EXTRA CARE TO
AVOID CONTACT WITH LIVE ELECTRICAL
CIRCUITS.

Teledyne Analytical Instruments 15

Introduction BDS 3960

Access Drawer: For access t o the BDS S ensor And pr essur e regul ator.
T he f ront panel sli des out when the four thumb screws ar e loosened.
Openi ng the int er ior gives access to most ci rcui t boards t oo.

1.5 Rear Panel (Equipment Interface)

The rear panel, shown in Figure 1-2, contains the gas and electrical
connectors for external inlets and outlets. The connectors are described
briefly here and in detail in Chapter 3 Installation. Except for gas, AC
power, and RS-232 communications I/O, all user connections for analog
output, alarms, calibration and remote probe contacts are available
through the 50 pin equipment interface connector. User connections
made at the rear panel include:

• Power Connection 110 VAC power source (220 VAC
optional.

• Gas Inlet and Outlet One inlet and one exhaust out.

• Moisture By-pass Additional vent line for condensate

• Analog Outputs 0–1 VDC oxygen concentr ation plus
0-1 VDC r ange I D, and isolated
4–20 mA DC oxygen concentr ation
plus 4-20 mA DC range ID.

• Alarm Connections 2 concentration alarms and 1
system alarm.

• Remote Probe Used in the BDS 3960 for
controlling external solenoid
valves only.

• Remote Span/Zero Digital inputs allow external
control of analyzer calibration.

• Calibration Contact To notify external equipment that
instrument is being calibrated and
readings are not monitoring
sample.•

Range ID Contacts Four separate, dedicated, range

relay contacts. Low, Medium,
High, Cal.

Teledyne Analytical Instruments 16

Oxygen Analyzer Introduction

Figure 1-2: Model BDS 3960 Rear Panel

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Operational Theory BDS 3960

Operational Theory

2.1 Introduction

The analyzer is composed of four subsystems:

• BDS Sensor

• Sample System

• Pocket PC

• Electronic I/O Signal Processing and Display

The sample system is designed to accept the sample gas and
transport it through the analyzer without contaminating or altering the
sample prior to analysis. The BDS Sensor is an electrochemical device
that translates the amount of oxygen present in the sample into an
electrical current. The Pocket PC processes the sensor signal and sends
messages to the I/O electronics to correctly display oxygen value as well
as control other signals to the customer interface. The Electronic I/O
signal processing amplifies the sensor signal, digitizes the sensor reading
and sends them to the pocket PC for processing. Then it receives
commands from the pocket PC to manipulate signals for the customer
interface.

2.2 BDS Sensor

2.2.1 Principles of Operation

The BDS oxygen sensor technology developed at Teledyne
Analytical Instruments is a result of TAI’s heavy investment on R&D
and expertise established during the half-century’s manufacturing of
electrochemical oxygen sensor. It stands for Bipotentiostat Driven
Sensor. A BDS oxygen sensor accurately translates the oxygen level in
the sample gas into to an electrical current signal.

A potentiostat contains three electrodes: a working electrode, a
reference electrode and a counter electrode. A Bipotentiostat is a
combination of two potentiostats that share the reference electrode and
the counter electrode. The potential at the working electrode is precisely

Teledyne Analytical Instruments 18

Oxygen Analyzer Operational Theory

controlled with respect to the reference electrode. The counter electrode
is used to carry the current that flow through the sensor. A potentiostat is
typically constructed with several operational amplifiers. The three
electrodes in an electrochemical cell and the operational amplifiers in
the potentiostat constitute a feedback-control loop. The potentiostat
technology has been well accepted in the field of electrochemistry, and
proven effective in eliminating polarization of the reference electrode
and automatic compensating electric resistance in the cell.

In a BDS oxygen sensor, the sensing electrode is a working
electrode that is under precise potential control as discussed above. A
stable sensing electrode potential is very critical for an oxygen sensor to
achieve high stability, low noise and large dynamic range. The reference
electrode in a BDS sensor is a Ag/Ag2O electrode which is well known
for its stable electrode potential and compatibility with the KOH
electrolyte in an oxygen sensor. The counter electrode is made of a
Platinum wire.

The sensing process involves electrochemical reactions inside the
sensor. At the sensing electrode, oxygen is reduced at the controlled
potential:

O

+ 2H2O + 4e

2

-

— > 4OH

-

There is no net electrochemical reaction at the reference electrode
since it is connected to the high impedance input of the operation
amplifier.

The electrochemical reaction at the counter electrode is:

4OH- — > O2 + 2H2 O + 4e

-

It is noteworthy that reaction (2) is reverse of the reaction (1). It is
indicative of a net change of zero inside a BDS sensor throughout the sensing
process. This feature produces a long-term stability for the BDS sensor.

There are two resources of oxygen being reduced at the sensing
electrode: from the sample gas and dissolved oxygen within the
electrolyte. The oxygen molecules in the sample gas diffuse to the
sensing electrode through a diffusion barrier (controlled diffusion) to
produce a current signal which is proportional to the oxygen level in the
sample gas. However, the dissolved oxygen in the electrolyte also
diffuses through the electrolyte. It is reduced at the sensing electrode and
produces a background current. This background current represents the
detection limit of an oxygen sensor.

(1)

( 2)

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Operational Theory BDS 3960

The main advantage of the BDS technology lies in the unique
second potentiostat. It is designed to remove dissolved oxygen and other
impurities in the electrolyte. It eliminates the internal background
current which previously limited the detection process.

The second potentiostat is located adjacent to the sensing electrode.
It uses a novel material, Reticulated Vitreous Carbon (RVC) and precise
control of the potential to remove the dissolved oxygen and impurities in
the electrolyte efficiently. As the result, the BDS sensor achieves an
outstanding feature of absolute zero output in the absence of oxygen.

Figure 2.1: Cross Section of the BDS Oxygen Sensor

Figure 2.1 shows the schematic of a BDS oxygen sensor. The
sample gas enters the sensor through the gas inlet port and exits at the
gas outlet. A portion of oxygen in the sample gas diffuses through the
diffusion barrier to be reduced at the sensing electrode to form OH- in
the electrolyte. OH- can move freely through the porous 2nd working
electrode. At the counter electrode, OH- is oxidized back to oxygen.

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Oxygen Analyzer Operational Theory

While the 2nd working electrode allows OH- to move through, it
prevents the dissolved oxygen from the top portion of the sensor to reach
the sensing electrode. The reference electrode provides a potential
reference for both the sensing electrode and the 2nd working electrode.

NOTE: BDS technology and sensor is a patent pending

technology of Teledyne Analytical Instruments in the
United State of America as well as many foreign countries.

To learn more about BDS technology, please visit TAI’s web page at
http://www.Teledyne-AI.com

To learn more about potentiostat, visit Electochemical Society’s web
page at http://www.electrochem.org

2.2.2 Gas Flow Rate

The output from a BDS oxygen sensor is relatively insensitive to
change of gas flow rate if operated in the range of 1 - 3 SCFH (in
nitrogen). The output drops when the flow rate is below 1 SCFH. Figure

2.2 is a typical curve showing the sensor outputs at different flow rate.

Figure 2.2: BDS sensor output at different gas flow rate

Teledyne Analytical Instruments 21

Operational Theory BDS 3960

O

2.2.3 Gas Pressure

The analyzer is equipped with a pressure regulator as shown in
Figure 2-3. To access the pressure regulator, the front panel must be
opened. The inlet pressure should be regulated anywhere between 4 to
50 psig. The sensor is not affected by pressure changes in the inlet as
long as the analyzer vents to atmosphere. If the analyzer is not vented to
atmosphere, the downstream pressure must not exceed 10 inch of water.
A clogged or restricted vent or excessive pressure will force gas into the
electrolyte and cause damage to the BDS sensor.

xygen Scrubber

Vent

Sample

Inlet

Span

Inlet

Pressure Regulator

Flowmeter

BDS Sensor

Figure 2-3: A simplified BDS Sample System

2.2.4 Temperature effect

The raw output from a BDS oxygen sensor has a temperature
coefficient about 0.25% / °C. That is an average value, it changes as
temperature changes. This temperature effect is compensated by the
software throughout the operation temperature range (5 – 40°C).

2.2.5 Recovery from High Level Oxygen Exposure

The ambient air contains about 210,000,000 ppb (2.1 x 108)
oxygen. Figure 2.4 is a typical purge-down curve for a new BDS sensor
which had been air saturated. It is normal to take several hours, even
days for an air saturated BDS to purge down to a low ppb level.

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Oxygen Analyzer Operational Theory

Figure 2.4 Typical Purge-down Curve After Air Saturation

S h or t e n i ng t h e ai r exp o s u r e wi l l al l o w a f a s t e r se ns o r r ec o v e r y.
A ty p i c a l BD S se n s o r wi l l re c o v e r t o 1 pp m i n ap p r ox i m a t el y 25
m i nu t e s , t o 10 0 pp b af t e r 80 m i n , an d 10 pp b i n ab ou t 8 ho u r s , af t e r
s u f f e r i n g a t e n- m i n u t e ex p os u r e to ai r .

2.2.6 Background Gas Compatibility

T he BDS oxygen sensor wi l l work in i ner t gas backgr ounds,
i ncludi ng ni t rogen, hydr ogen, ar gon, heli um and ethane. The sensor
out put, however, i s dif fer ent in di ff erent backgr ound gases. For exam pl e,
t he sensor output i n a hydr ogen background is twi ce as much as it woul d
be in a ni tr ogen background. Therefor e, i t is recom mended to cali br ate t he
analyzer wit h an oxygen standar d that has a sim il ar background as the
sam pl e gas. If an oxygen st andar d is unavai l able for a par ti cul ar
background, a Gas F act or which is det er mi ned at TAI coul d be used t o
cor rect the sensor out put in dif f er ent backgr ound (see sect ion 4.3.9) .

Note: the gas flow meter in the analyzer is calibrated for air. The

error for measuring nitrogen is usually negligible. But for

Teledyne Analytical Instruments 23