Teledyne P-NM70946, 3000 User Manual

Trace Oxygen Analyzer

OPERATING INSTRUCTIONS FOR

Model

Ultra Trace 3000

Oxygen Analyzer

DANGER

HIGHLY TOXIC AND OR FLAMMABLE LIQUIDS OR GASES MAY BE PRESENT IN THIS MONITORING SYSTEM.

PERSONAL PROTECTIVE EQUIPMENT MAY BE REQUIRED WHEN SERVICING THIS SYSTEM. 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

P/N M70946

12/10/99

ECO # 99-0483

Model Ultra Tace 3000

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

This instrument provides measurement readings to its user, and serves as a tool by which valuable data can be gathered. The information provided by the instrument may assist the user in eliminating potential hazards caused by his process; however, it is essential that all personnel involved in the use of the instrument or its interface, with the process being measured, be properly trained in the process itself, as well as all instrumentation related to it.

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

Trace 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:

G Ultra Trace 3000-V: Instrument configured for Vacuum Service G 19" Rack Mnt: The 19" Relay Rack Mount units are available with one

Ultra Trace 3000 series analyzers installed in a standard 19" panel and ready to mount in a standard rack.

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Model Ultra Tace 3000

Table of Contents

1 Introduction

1.1 Overview........................................................................ 1-1

1.2 Typical Applications ....................................................... 1-1

1.3 Main Features of the Analyzer ....................................... 1-1

1.4 Model Designations....................................................... 1-2

1.5 Front P anel (Operator Interface)..................................... 1-3

1.6 Rear Panel (Equipment Interf ace).................................. 1-5

2 Operational Theory

2.1 Introduction .................................................................... 2-1

2.2 Micro-Fuel Cell Sensor .................................................. 2-1

2.2.1 Principles of Operation ............................................ 2-1

2.2.2 Anatomy of a Micro-Fuel Cell .................................. 2-2

2.2.3 Electrochemical Reactions...................................... 2-3

2.2.4 The Effect of Pressure.............................................. 2-4

2.2.5 Calibration Characteristics ...................................... 2-4

2.2.6 TEC Cooling System ............................................... 2-4

2.3 Sample System.............................................................. 2-5

2.4 Electronics and Signal Processing ................................ 2-8

3 Installation

3.1 Unpacking the Analyzer................................................. 3-1

3.2 Mounting the Analyzer ................................................... 3-1

3.3 Rear Panel Connections................................................ 3-3

3.3.1 Gas Connections ................................................... 3-3

3.3.2 Electrical Connections........................................... 3-4

3.3.2.1 Primary Input Po wer....................................... 3-4

3.3.2.2 50-pin Interface Connector............................. 3-5

3.3.3 Remote Probe Connector ...................................... 3-8

3.4 Installing the Micro-Fuel Cell ......................................... 3-10

3.5 Testing the System......................................................... 3-10

4 Operation

4.1 Introduction .................................................................... 4-1

4.2 Using the Data Entry and Function Buttons ................... 4-2

4.3 The

4.3.1 Tracking the O2 Readings during CAl & Alarm ....... 4-4

4.3.2 Setting up an Auto-Cal........................................... 4-5

4.3.3 Password Protection .............................................. 4-6

System

4.3.3.1 Entering the Password................................... 4-7

Function ..................................................... 4-3

Teledyne Analytical Instruments

Trace Oxygen Analyzer

4.3.3.2 Installing or Changing the Password ............. 4-8

4.3.4 Logout.................................................................... 4-9

4.3.5 System Self-Diagnostic Test .................................. 4-9

4.3.6 Version Screen ...................................................... 4-10

4.3.7 Filter Function........................................................ 4-11

4.4 Calibration of the Analyzer............................................. 4-11

4.4.1 Zero Cal................................................................. 4-11

4.4.1.1 Auto Mode Zeroing ........................................ 4-12

4.4.1.2 Manual Mode Zeroing.................................... 4-13

4.4.1.3 Cell Failure .................................................... 4-13

4.4.2 Span Cal................................................................ 4-14

4.4.2.1 Auto Mode Spanning ..................................... 4-14

4.4.2.2 Manual Mode Spanning................................. 4-15

4.4.3 Span Failure .......................................................... 4-16

4.5 Switching of Sample Streams ........................................ 4-17

4.5.1 Special notes on hydrogen gas stream.................. 4-17

4.6 The

4.7 The

4.7.1 Setting the Analog Output Ranges......................... 4-20

4.7.2 Fixed Range Analysis ............................................ 4-21

4.8 The

4.9 Signal Output ................................................................. 4-23

Alarms Range

Analyze

Function...................................................... 4-17

Function ...................................................... 4-20

Function.................................................... 4-23

Maintenance

5.1 Routine Maintenance..................................................... 5-1

5.2 Cell Replacement .......................................................... 5-1

5.2.1 Storing and Handling Replacement Cells ............... 5-1

5.2.2 When to Replace a Cell........................................... 5-2

5.2.3 Removing the Micro-Fuel Cell ................................. 5-2

5.2.4 Installing a New Micro-Fuel Cell.............................. 5-4

5.2.5 Cell W arranty ........................................................... 5-4

5.3 Fuse Replacement ......................................................... 5-5

5.4 System Self Diagnostic Test........................................... 5-5

5.5 Major Internal Components............................................ 5-6

5.6 Cleaning ........................................................................ 5-7

5.7 Troubleshooting ............................................................. 5-8

Appendix

A-1 Model Ultra Tace 3000 Specifications ............................ A-1

A-2 Recommended 2-Year Spare Parts List ......................... A-3

A-3 Drawing List................................................................... A-4

A-4 19-Inch Relay Rack Panel Mount................................... A-4

A-5 Application Notes on Pressures and Flow..................... A-5

Teledyne Analytical Instruments

Model Ultra Tace 3000

COMBUSTIBLE GAS USAGE WARNING

This is a general purpose instrument designed for use 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.

D ANGER

The customer should ensure that the principles of operation 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 Teled yne, no responsibility b y Teled yne, its affiliates, and agents for damage or injury from misuse or neglect of this equipment is implied or assumed.

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Ultra Trace Oxygen Analyzer Introduction 1

Introduction

1.1 Overview

The Teledyne Analytical Instruments Model 3000 Ultra Trace Oxygen Analyzer is a versatile microprocessor-based instrument for detecting oxygen at the parts-per-billion (ppb) level in a variety of gases. This manual covers the Model Ultra Trace 3000 General Purpose flush-panel and/or rack-mount units only. These units are for indoor use in a nonhazardous environment.

1.2 Typical Applications

A few typical applications of the Model Ultra Trace 3000 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 3000 Ultra Trace Oxygen Analyzer is sophisticated yet simple to use. The main features of the analyzer include:

• A 2-line alphanumeric vacuum fluorescent display (VFD) screen, driven by microprocessor electronics, that continuously prompts and informs the operator.

• High resolution, accurate readings of oxygen content from low ppm levels through 25%. Large, bright, meter readout.

• Stainless steel cell block (wetted surfaces).

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1 Introduction Model Ultra Trace 3000

• Advanced Micro-Fuel Cell, designed for trace analysis, has a 0250 ppb low range with less than a 100 ppb offset and six months warranty and an expected lifetime of one year.

• Versatile analysis over a wide range of applications.

• Microprocessor based electronics: 8-bit CMOS microprocessor

with 32 kB RAM and 128 kB ROM.

• Three user definable output ranges (from 0-250 ppb through 01000 ppm) allow best match to users process and equipment, plus a fixed 1000 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 onto a specific range of interest.

• Two adjustable concentration alarms and a system failure alarm.

• Extensive self-diagnostic testing, at startup and on demand, with

continuous power-supply monitoring.

• Two way RFI protection.

• RS-232 serial digital port for use with a computer or other digital

communication device.

• Four analog outputs: two for measurement (0–1 V dc 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 Model Designations

Ultra Trace 3000: Standard model for sample under pressure Ultra Trace 3000-V: Instrument configured for Vacuum Service

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Ultra Trace Oxygen Analyzer Introduction 1

1.5 Front Panel (Operator Interface)

The standard Ultra Trace 3000 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 thirteen buttons for operating the analyzer, a digital meter, an alphanumeric display, and a window for viewing the sample flowmeter.

Function Keys: Six touch-sensitive membrane switches are used to change the specific function performed by the analyzer:

Digital Meter

Alphanumer ic Display

Door Latc h

Sample System Flow Indicator

Standby Switch

Data Entry Buttons

Function Buttons

Figure 1-1: Model Ultra Trace 3000 Front Panel

• Analyze Perform analysis for oxygen content of a sample gas.

• System Perform system-related tasks (described in detail in

chapter 4, Operation.).

• Span Span calibrate the analyzer.

• Zero Zero calibrate the analyzer.

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1 Introduction Model Ultra Trace 3000

• Alarms Set the alarm setpoints and attributes.

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

Data Entry Keys: Six touch-sensitive membrane switches are used to

input data to the instrument via the alphanumeric VFD display:

• Left & Right Arrows Select between functions currently

displayed on the VFD screen.

• Up & Down Arrows Increment or decrement values of

functions currently displayed.

• Enter Moves VFD display on to the next screen in a series. If

none remains, returns to the

• Escape Moves VFD display back to the previous screen in a

series. If none remains, returns to the

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 ppb and then switches to a continuous ppm readout from 0-9999.9 ppm. It is accurate across all analysis ranges without the discontinuity inherent in analog range switching.

Analyze

screen.

Analyze

screen.

Alphanumeric Interface Screen: The VFD screen is an easy-to-use

interface from operator to analyzer. It displays values, options, and messages that give the operator immediate feedback.

NeedleValve: To adjust flow of gas sample Flowmeter: Monitors the flow of gas past the sensor. Readout is 0.2 to

2.4 standard liters per minute (SLPM) of nitrogen

 Standby Button: The Standby turns off the display and outputs,

but circuitry is still operating.

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 .

Access Door: For access to the Micro-Fuel Cell, the front panel

swings open when the latch in the upper right corner of the panel is pressed

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Ultra Trace Oxygen Analyzer Introduction 1

all the way in with a narrow gauge tool. Accessing the main circuit board requires unfastening rear panel screws and sliding the unit out of the case.

1.6 Rear Panel (Equipment Interface)

The rear panel, shown in Figure 1-2, contains the gas and electrical connectors for external inlets and outlets. Some of those depicted are optional and may not appear on your instrument. The connectors are described briefly here and in detail in chapter 3 Installation.

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

Figure 1-2: Model Ultra Trace 3000 Rear Panel

• Power Connection Universal AC power source.

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

• Analog Outputs 0–1 V dc oxygen concentration plus 0-1

V dc range ID, and isolated 4–20 mA dc oxygen concentration plus 4-20 mA dc range ID.

• Alarm Connections 2 concentration alarms and 1 system

alarm.

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1 Introduction Model Ultra Trace 3000

• RS-232 Port Serial digital concentration signal output

and control input.

• Remote Probe Used in the Ultra Trace3000 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.

• Network I/O Serial digital communications for local

network access. For future expansion. Not implemented at this printing.

Note: If you require highly accurate Auto-Cal timing, use external

Auto-Cal control where possible. The internal clock in the Model Ultra Trace 3000 is accurate to 2-3 %. Accordingly, internally scheduled calibrations can vary 2-3 % per day.

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Ultra Trace Oxygen Analyzer Operational Theory 2

Operational Theory

2.1 Introduction

The analyzer is composed of three subsystems:

1. Micro-fuel Cell Sensor

2. Sample System

3. Electronic Signal Processing, Display and Control

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 Micro-fuel Cell is an electrochemical galvanic device that translates the amount of oxygen present in the sample into an electrical current. The electronic signal processing, display and control subsystem simplifies operation of the analyzer and accurately processes the sampled data. The microprocessor controls all signal processing, input/output and display functions for the analyzer.

2.2 Micro-Fuel Cell Sensor

2.2.1 Principles of Operation

The oxygen sensor used in the Model Ultra Trace 3000 series is a Micro-fuel Cell, Model B-2CXL designed and manufactured by Analytical Instruments. It is a sealed plastic disposable electrochemical transducer.

The active components of the Micro-fuel Cell are a cathode, an anode, and the aqueous KOH electrolyte in which they are immersed. The cell converts the energy from a chemical reaction into an electrical current in an external electrical circuit. Its action is similar to that of a battery.

There is, however, an important difference in the operation of a battery as compared to the Micro-fuel Cell: In the battery, all reactants are stored within the cell, whereas in the Micro-fuel Cell, one of the reactants (oxygen)

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2 Operational Theory Model Ultra Trace 3000

comes from outside the device as a constituent of the sample gas being analyzed. The Micro-Fuel Cell is therefore a hybrid between a battery and a true fuel cell. (All of the reactants are stored externally in a true fuel cell.)

2.2.2 Anatomy of a Micro-Fuel Cell

The Micro-Fuel Cell is a cylinder only 1¼ inches in diameter and 1¼ inches thick. It is made of an extremely inert plastic, which can be placed confidently in practically any environment or sample stream. It is effectively sealed, although one end is permeable to oxygen in the sample gas. The other end of the cell is a contact plate consisting of two concentric foil rings. The rings mate with spring-loaded contacts in the sensor block assembly and provide the electrical connection to the rest of the analyzer. Figure 2-1 illustrates the external features.

Figure 2-1: Micro-fuel Cell

Refer to Figure 2-2, Cross Section of a Micro-Fuel Cell, which illustrates the following internal description.

Figure 2-2. Cross Section of a Micro-Fuel Cell (not to scale)

At the top end of the cell is a diffusion membrane of Teflon, whose thickness is very accurately controlled. Beneath the diffusion membrane lies

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Ultra Trace Oxygen Analyzer Operational Theory 2

the oxygen sensing element—the cathode—with a surface area almost 4 cm2. The cathode has many perforations to ensure sufficient wetting of the upper surface with electrolyte, and it is plated with an inert metal.

The anode structure is below the cathode. It is made of lead and has a proprietary design which is meant to maximize the amount of metal available for chemical reaction.

At the rear of the cell, just below the anode structure, is a flexible membrane designed to accommodate the internal volume changes that occur throughout the life of the cell. This flexibility assures that the sensing membrane remains in its proper position, keeping the electrical output constant.

The entire space between the diffusion membrane, above the cathode, and the flexible rear membrane, beneath the anode, is filled with electrolyte. Cathode and anode are submerged in this common pool. They each have a conductor connecting them to one of the external contact rings on the contact plate, which is on the bottom of the cell.

2.2.3 Electrochemical Reactions

The sample gas diffuses through the Teflon membrane. Any oxygen in the sample gas is reduced on the surface of the cathode by the following HALF REACTION:

O2 + 2H2O + 4e

––

–

––

→ 4OH

––

–

––

(cathode)

(Four electrons combine with one oxygen molecule—in the presence of water from the electrolyte—to produce four hydroxyl ions.)

When the oxygen is reduced at the cathode, lead is simultaneously oxidized at the anode by the following HALF REACTION:

Pb + 2OH

––

–

––

→ Pb+2 + H2O + 2e

––

–

––

(anode)

(Two electrons are transferred for each atom of lead that is oxidized. Therefore it takes two of the above anode reactions to balance one cathode reaction and transfer four electrons.)

The electrons released at the surface of the anode flow to the cathode surface when an external electrical path is provided. The current is proportional to the amount of oxygen reaching the cathode. It is measured and used to determine the oxygen concentration in the gas mixture.

The overall reaction for the fuel cell is the SUM of the half reactions above, or:

2Pb + O2 → 2PbO

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2 Operational Theory Model Ultra Trace 3000

(These reactions are specific to oxygen as long as no gaseous components capable of oxidizing lead—such as iodine, bromine, chlorine and fluorine—are present in the sample.)

In the absence of oxygen, no current is generated.

2.2.4 The Effect of Pressure

In order to state the amount of oxygen present in the sample in ppb or parts-per-million of the gas mixture, it is necessary that the sample diffuse into the cell under constant pressure.

If the total pressure increases, the rate that oxygen reaches the cathode through the diffusing membrane will also increase. The electron transfer, and therefore the external current, will increase, even though the oxygen concentration of the sample has not changed. It is therefore important that the sample pressure at the fuel cell (usually vent pressure) remain relatively constant between calibrations.

2.2.5 Calibration Characteristics

Given that the total pressure of the sample gas on the surface of the Micro-Fuel Cell input is constant, a convenient characteristic of the cell is that the current produced in an external circuit is directly proportional to the rate at which oxygen molecules reach the cathode, and this rate is directly proportional to the concentration of oxygen in the gaseous mixture. In other words it has a linear characteristic curve, as shown in Figure 2-3. Measuring circuits do not have to compensate for nonlinearities.

In addition, since there is zero output in the absence of oxygen, the characteristic curve has close to an absolute zero (less than ± 0.1 ppm oxygen). Depending upon the application, zeroing may still be used to compensate for the combined zero offsets of the cell and the electronics.

2.2.6 TEC Cooling System

Ultra Trace 3000 analyzers include an advance Thermal Electric Cooler (TEC) system. This system enhances the performance of the Micro-fuel Cell by cooling it and regulating its operating temperature. The TEC system includes a TEC module, a temperature control PCB, a separate power supply, a thermistor, and a special insulated cellblock. The system is used to regulate the cell temperature at 11 degrees C. Operating the Micro-fuel Cell at a low

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Ultra Trace Oxygen Analyzer Operational Theory 2

temperature minimizes the cell offset (typically less than 75 PPB). A second benefit of the TEC system is that by regulating the cell temperature the analyzer becomes tolerant of thermal transients.

The TEC module is a solid-state semiconductor heat – pump. Passing DC current through the TEC module produces heat flow though the device. One side of the device will become hot and the other side will become cold. The TEC module is attached to a heat-sink which is cooled by a fan. This is required to maintain the hot side at an acceptable temperature. The hot side temperature limits the overall performance of the TEC module. The fan draws air into the bottom of the analyzer, this air is forced over the heat sink and exits through the left side of the analyzer. The power for the TEC device is supplied by a Pulse Width Modulated (PWM) proportional switching temperature controller. The temperature controller PCB supplies a 12 volt pulse whose duty cycle is proportional to the cooling required. The temperature controller PCB uses a thermistor to monitor the temperature of the of cell block. Power for the fan, and the temperature controller PCB is supplied by a separate 12VDC power supply.

Figure 2-3. Characteristic Input/Output Curve for a Micro-Fuel Cell

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2 Operational Theory Model Ultra Trace 3000

2.3 Sample System

The sample system delivers gases to the Micro-Fuel Cell sensor from the analyzer rear panel inlet. Depending on the mode of operation either sample or calibration gas is delivered.

The Model Ultra Trace 3000 sample system is designed and fabricated to ensure that the oxygen concentration of the gas is not altered as it travels through the sample system.

The sample system for the standard instrument incorporates 1/4" VCR for sample inlet and outlet tube connections at the rear panel. The sample or calibration gas that flows through the system is monitored by a flowmeter downstream from the cell. Figure 2-4 shows the piping layout and flow diagram for the standard model.

2-6

Figure 2-4: Piping Layout

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Ultra Trace Oxygen Analyzer Operational Theory 2

Figure 2-5: Flow Diagram-Sample Under Pressure

-Standard Model Ultra Trace 3000

-Do not exceed 10" Hg Vacuum-

Figure 2-5-1: Flow Diagram-Sample at Zero Pressure

-Model Ultra Trace 3000-V

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2 Operational Theory Model Ultra Trace 3000

Figure 2-5 is the flow diagram for the sampling system. In the standard instrument, calibration gases can be connected directly to the Sample In port by teeing to the port with appropriate valves.

2.4 Electronics and Signal Processing

The Model Ultra Trace 3000 Oxygen Analyzer uses an 8031 microcontroller with 32 kB of RAM and 128 kB of ROM to control all signal processing, input/output, and display functions for the analyzer. System power is supplied from a universal power supply module designed to be compatible with any international power source. Figure 2-6 shows the location of the power supply and the main electronic PC boards.

The signal processing electronics including the microprocessor, analog to digital, and digital to analog converters are located on the motherboard at the bottom of the case. The preamplifier board is mounted on top of the motherboard as shown in the figure. These boards are accessible after removing the back panel. Figure 2-7 is a block diagram of the Analyzer electronics.

Power Supply

Front Panel

Display Board

Preamplifier

PCB

Figure 2-6: Electronic Component Location Inside the Model Ultra Trace 3000

Universal

TEC Power Supply

Slide-out Electronics Drawer

Temperature

Controller

Board

Motherboard

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Ultra Trace Oxygen Analyzer Operational Theory 2

Sensor

Thermistor

T E C

FAN

Temperature Controller

HEAT

SINK

Current

to V oltage

Amplifier

Auto

Range

Second

Stage

Amplifier

Power

Supply

System

Failure

Alarm

A to D

Converter

Micro-

Processor

0-1 V

4-20 mA

0-1 V

4-20 mA

Displays

Processing

Self Test Signal

Concentration

D to A

Converter

Range

Figure 2-7: Block Diagram of the Model Ultra Trace 3000 Electronics

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2 Operational Theory Model Ultra Trace 3000

In the presence of oxygen the cell generates a current. A current to voltage amplifier converts this current to a voltage, which is further amplified in the second stage amplifier.

The output from the second stage amplifier is sent to an 18 bit analog to digital converter controlled by the microprocessor.

The digital concentration signal along with input from the control panel is processed by the microprocessor, and appropriate control signals are directed to the display, alarms and communications port. The same digital information is also sent to a 12 bit digital to analog converter that produces the 4-20 mA dc and the 0-1 V dc analog concentration signal outputs, and the analog range ID outputs.

Signals from the power supply are also monitored, and through the microprocessor, the system failure alarm is activated if a malfunction is detected.

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