(Product shown with optional flow meter and pressure regulator)
Alpha Omega Instruments Corp.
40 Albion Road, Suite 100
Lincoln, RI 02865
Phone: 401-333-8580
Fax: 401-333-5550
Website: www.aoi-corp.com
Email: contact@aoi-corp.com
VERSION 2.0 COPYRIGHT 06/16
ALPHA OMEGA INSTRUMENTS CORP. ALL RIGHTS
RESERVED INCLUDING THE RIGHT TO REPRODUCE
THIS MANUAL, OR ANY PORTION THEREOF, IN ANY FORM.
Alpha Omega Instruments Corp. warrants the products delivered to be free from defects in material
and workmanship at the time of delivery to the FOB point specified in the purchase order, its liability
under this warranty being limited to repairing or replacing, at Alpha Omega Instruments option, items
(excluding the oxygen sensor) which are returned to it prepaid within two (2) years from the date of
shipment and found to Seller’s satisfaction to be defective.
Alpha Omega Instruments one (1) year sensor warranty offers protection for one full year from the
date of shipment of the Series 3520 Portable Oxygen Analyzer. Any sensor from a Series 3520
Portable Oxygen Analyzer that fails under normal use must be returned to Seller prepaid and, if such
sensor is determined by Seller to be defective, Seller shall provide Buyer a replacement sensor. Buyer
must provide the serial number of the analyzer from which the sensor has been removed. If a sensor
is found to be defective and a new one issued, the warranty of the replacement sensor (s) is for a
period of one year from the date of shipment. At times, it may be necessary to ship a replacement
sensor in advance of receiving one returned for warranty claim. In such cases, if the returned sensor is
not covered under warranty, the user will be charged the full price of a replacement sensor. In no
event shall Alpha Omega Instruments Corp. be liable for consequential damages. NO PRODUCT IS
WARRANTED AS BEING FIT FOR A PARTICULAR PURPOSE AND THERE IS NO WARRANTY OF
MERCHANTABILITY.
This warranty applies only if:
(i) the items are used solely under the operating conditions and manner
recommended in this manual, specifications, or other literature;
(ii) the items have not been misused or abused in any manner or repairs attempted
thereon;
(iii) written notice of the failure within the warranty period is forwarded to Alpha
Omega Instruments Corp. and, the directions received for properly identifying
items returned under warranty are followed;
(iv) the return notice authorizes Alpha Omega Instruments Corp. to examine and
disassemble returned products to the extent the Company deems necessary to
ascertain the cause of failure.
The warranties stated herein are exclusive. THERE ARE NO OTHER WARRANTIES, EITHER
EXPRESSED OR IMPLIED, BEYOND THOSE SET FORTH HEREIN, and Alpha Omega Instruments
Corp. does not assume any other obligation or liability in connection with the sale or use of said
products.
Disclaimer of Warranty
Alpha Omega Instruments Corp. makes no representation or warranties, either expressed or implied, by or with
respect to anything in this manual, including, but not limited to, implied warranties of merchantability or fitness for
a particular purpose. In no event will Alpha Omega Instruments Corp. be liable for any damages, whether direct or
indirect, special, consequential, or incidental arising from the use of this manual. Some states in the USA do not
allow the exclusion of incidental or consequential damages. Alpha Omega Instruments Corp. also reserves the
right to make any changes to improve the performance of its products at any time and without notice.
The Series 3520 Portable Oxygen Analyzer is a portable trace oxygen analyzer designed to provide
accurate and dependable trace oxygen measurements in a variety of gases. The analyzer enclosure
is made from durable polycarbonate and is rated NEMA 1 for general purpose service. The instrument
is powered from eight AA NICAD batteries that are mounted internal to the analyzer. Recharging of
the batteries is done with a 115 VAC/60 Hz adapter that is shipped with the instrument. Options
include a pressure regulator, flowmeter, in-line filter, and pump.
Advanced Sensor Technology
The Series 3520 Portable Oxygen Analyzer features an advanced trace oxygen sensor. The sensor is
a lead-oxygen battery comprised of a lead anode, a gold plated cathode, and an electrolyte consisting
of potassium hydroxide. All types of electrochemical transducers have three primary components; a
cathode, anode, and electrolyte. In the Alpha Omega Instruments advanced sensor, the cathode is the
sensing electrode or the site where chemical reduction of the oxygen takes place.
The chemical reactions are as follows:
Cathode Reaction4e- + O2 + 2H2O 4OH- (1)
In the above reaction, four electrons combine with one oxygen molecule to produce four hydroxyl ions.
This cathodic half-reaction occurs simultaneously with the following anodic half-reaction:
Anode ReactionPb + 2OH-PbO + H2O + 2e(2)
The anode (lead) is oxidized (in a basic media) to lead oxide and in the process, two electrons are
transferred for each atom of lead that is oxidized. The sum of the half-reactions (1) and (2) results in
the overall reaction (3):
Overall ReactionO2 + 2Pb 2PbO(3)
From this reaction it can be seen that the sensor is very specific for oxygen providing there are no
gaseous components in the sample stream capable of oxidizing lead. The only likely compounds that
meet this requirement are the halogens (iodine, bromine, chlorine, and fluorine).
In reaction (1), four electrons are transferred for each oxygen molecule undergoing reaction. In order
to be reacted, and oxygen molecule must diffuse through both the sensing membrane and the thin film
of electrolyte maintained between the sensing membrane and the upper surface of the cathode. The
rate at which oxygen molecules reach the surface of the cathode determines the electrical output.
This rate is directly proportional to the concentration of oxygen in the gaseous mixture surrounding the
sensor cell.
Upon opening the shipping container, carefully unpack the analyzer to check if the outer surfaces have
been damaged. If so, report the findings immediately to Alpha Omega Instruments who will provide
further instructions. If there is no apparent damage, check the contents
to ensure all items were shipped. In some cases, items may be backordered.
All damage and shortage claims must be made
known to Alpha Omega Instruments within 10 days
after receipt of shipment.
Powering the Series 3520 Portable Oxygen Analyzer
The Series 3520 Portable Oxygen Analyzer is powered from eight AA NICAD batteries that are
mounted internal to the instrument. Recharging of the batteries is done with a 115 VAC/60 Hz adapter
that is shipped with the analyzer. To power up the instrument, place the front panel on/off switch to the
“ON” position. When the Series 3520 Portable Oxygen Analyzer is attached to the AC/DC adapter, the
NICAD batteries are being charged at the same time. If the batteries are allowed to run below the level
where normal operation can be sustained, the charge time will be approximately 16 hours. In the
event the batteries need to be replaced, use only NICAD batteries (Panasonic Type P-60AAR or
equivalent). Use of any other type of battery may damage the instrument and void the warranty.
Recharging the NICAD Batteries
The Series 3520 will provide in excess of 48 hours (without the optional pump) of continued operation
before battery recharging is required. If the pump is in use, up to 12 hours of continued use can be
achieved. To recharge the NICAD batteries, connect the 3.5 mm plug from the 12 VDC wall mounted
AC/DC adapter to the jack located on the rear of the instrument (see Figure 1.0). Allow 16 hours to
fully recharge the batteries. Though the analyzer can be used while recharging, if the optional pump is
in use during this time recharging will take an additional 5-10% longer.
Replacing the NICAD Batteries
The internal NICAD batteries are located in two banks of 4 size AA NICAD battery trays accessible on
the top of the instrument. If battery replacement becomes necessary the following steps should be
followed:
Use only Panasonic Type P-60AAR or
equivalent NICAD batteries with the Series
3520 Portable Oxygen Analyzer
To remove a battery pack tray, push the tabs (located at each end of the tray) towards each other to
release the latches and pull the trays out from the enclosure.
Replace the defective batteries immediately and properly dispose of them. Be sure the replacement
batteries are Panasonic Type P-60AAR or equivalents. Do not mix battery types and use only the
NICAD types described in this manual. Use of other types of batteries may result in damage to the
analyzer and will void its warranty. After replacing the batteries, install the trays making sure that they
are fully inserted into their holder and that the tabs have fully latched.
Battery Status Check
As stated previously, the Series 3520 Portable Oxygen Analyzer is equipped with an analyzer on/off
power switch. This switch serves three functions. When placed in the middle “OFF” position, all power
to the instrument has been removed. This is the recommended position for storage, when recharging
the batteries, or replacing the sensor. When placed in the “ON” position, the analyzer is powered and
will display the measured oxygen value of the sample gas. If the optional pump has been included with
the Series 3520 Portable Oxygen Analyzer, placing the switch in the “ON” position also energies the
pump on/off switch. The third position associated with this switch allows the user to check the status of
the batteries. By placing the switch in the “Battery” position, the digital display indicates the voltage of
the battery pack. If the battery voltage indicated in the panel meter is 6 volts or less, recharging is
necessary. Caution: If the Series 3520 is equipped with a pump, be sure the pump is operating when
checking the batteries. The “Battery” check position is designed to be momentary so it cannot be left in
that position permanently.
For sample gases and/or calibration gases that are under pressure, it is imperative that the sample
gas pressure to the sensor be kept to under 1 pound per square inch. If it is expected to be in excess
of 1.0 psi, a pressure regulator should be used. There is no automatic pressure correction so
operation at a constant pressure will provide optimum measuring conditions. Vacuums to 12.5 psia are
permissible. Any vacuum level greater than that should be avoided as it will cause irreparable damage
to the sensor.
Range Identification
The Series 3520 Portable Oxygen Analyzer is available in seven (7) different ranges. To identify the
specific range of the analyzer in question, please refer to the original purchase order document or
invoice from Alpha Omega Instruments. In it, you will find a model number starting with the number
“3520”. The letter immediately following "3520" is the range identifier. The various ranges, with their
associated identifier, are as follows:
Range (ppm)Identifier
0-50 B
0-100 C
0-500 D
0-1,000 E
0-5,000 F
0-10,000 G
0-20,000 H
Sample Connections
The sample flow connections to the Series 3520 Portable Trace Oxygen Analyzer are standard ¼”
compression fittings. Referencing the model number designation once again, a number “1” directly
after the range identifier indicates that the instrument has been supplied with standard compression
fittings.
Electrical Output
The Series 3520 Portable Oxygen Analyzer is not equipped with an analog output for use with a
recorder, datalogger, etc.
Analyzer Storage
When the Series 3520 Portable Trace Oxygen Analyzer is not in use, it may be stored in any position.
If stored in an atmosphere where the temperature is greatly different from the temperature where it will
be used, the instrument should be allowed to come into equilibrium with the operating ambient
temperature before use. Under no circumstances should the Series 3520 Portable Trace Oxygen
Analyzer be exposed to temperatures below 32°F. Doing so will damage the sensor and void the
warranty.
The Series 3520 Portable Trace Oxygen Analyzer has been calibrated at the factory prior to shipment.
However, with the potential hazards associated with shipping instrumentation, it is advisable that the
analyzer be given a system calibration check prior to start-up. Alpha Omega Instruments trace oxygen
sensors feature high accuracy and excellent long term stability characteristics. As a result, routine
maintenance is kept to a minimum. As is the case with all gas analyzers, it is advisable to periodically
check the overall system calibration. The frequency of these checks is often determined by in-house
calibration protocols. If none exists, Alpha Omega Instruments Corp. recommends a calibration check
be made once every 2-3 months.
Calibration Gas
The oxygen sensor used in the Series 3520 Portable Trace Oxygen Analyzer has a linear output. As a
result, it can be calibrated using a single calibration gas as long as the test is performed accurately.
The calibration gas should contain a defined concentration of oxygen with a balance of nitrogen (N2).
The actual concentration of oxygen should be chosen based on the range of the instrument. The
factory recommends the calibration gas should be somewhere between 30%-70% of the analyzer's full
scale range. For instance, if the analyzer has a range of 0-1,000 ppm, the calibration gas should
contain between 300-700 ppm O2/balance N2. Most major gas manufacturers are good sources for
calibration gases.
Procedure for Checking Calibration
1. Select a cylinder of calibration gas as described above.
2. When selecting a pressure regulator to use with the cylinder gas, it is advisable to use a twostage regulator with the second stage capable of delivering a gas sample at a pressure of under
1.0 psig. Also, be sure to choose a regulator with a metal diaphragm, preferably stainless steel.
3. In addition to the selection of the pressure regulator, care must be given to choose the correct
sample tubing materials. For trace oxygen measuring applications, stainless steel tubing should
be used. An alternate choice is copper.
DO NOT USE RUBBER OR PLASTIC TUBING. AIR
CONTAINS 209,000 PPM OF OXYGEN. A MINUTE LEAK
OF AIR INTO EITHER THE CALIBRATION GAS OR SAMPLE
GAS LINE CAN CAUSE SIZEABLE ERRORS IN READINGS.
LEAKAGE CAN BE THROUGH CRACKS IN THE TUBING
OR BY DIFFUSION THROUGH THE TUBING.
4. Install a flowmeter on the discharge side of the sensor. Because the flowmeter is on the
discharge side, the materials of construction are of no significance to the trace oxygen readings
obtained.
5. Place power on to the Series 3520 Portable Trace Oxygen Analyzer and set the calibration gas
flow rate to 0.5 liter per minute (LPM). Monitor the analyzers response to the calibration gas,
waiting until a stable reading has been established.
6. Once the reading has stabilized, check the system for gas leaks. This is best done when step 5
has been completed. An easy method of determining the leak integrity of the system is to vary
the flow rate of the calibration gas. If increasing the flow rate from 0.5 LPM to 1 LPM causes a
drop in the reading, there is a good chance that somewhere between the gas source and inlet to
the sensor there is a leak. Check all gas fittings, connections, etc. using Snoop liquid leak
detector (Snoop is a registered trademark of NUPRO Co., 4800 East 345th Street, Willoughby,
Ohio 44094).
7. The reading in the LCD should now display the oxygen concentration of the calibration gas. BE
SURE TO ALLOW THE READING TO COME INTO EQUILIBRIUM BEFORE MAKING ANY
ADJUSTMENTS.
8. If the oxygen value read from the LCD differs from the calibration gas, a span adjustment should
be made. Locate the calibration potentiometer on the front panel of the instrument. To adjust
the meter reading to equal that of the calibration gas, slide the locking mechanism located at the
base of the potentiometer to the left. Turn the adjustment knob so that the value displayed in the
meter equals that of the calibration gas and allow the reading to stabilize for 2-3 minutes. Lock
the adjustment knob by sliding the locking mechanism to the right being careful not to
inadvertently turn the adjustment knob in the process. Calibration has been completed and
normal operation can be resumed.
Zero Adjustment
Alpha Omega Instrument's Trace Oxygen Sensor is specific for oxygen. When there is no oxygen
present, the output from the sensor is zero. This coupled with the inherent linear characteristics of
the sensor allow the user to use a single point calibration as means of calibrating the system. NO
ZERO CALIBRATION IS REQUIRED.
Alpha Omega Instruments oxygen sensor is designed to operate for prolonged periods of time without
needing replacement. However, in time the sensor's output will drop to a level where replacement
becomes the prudent course of action. A good indication of this is when there is an increase in the
requirement for routine calibration. When this happens, a replacement sensor should be ordered
directly from the factory.
To install a new sensor follow the directions below:
1. Shut-off power to the analyzer and disconnect the gas inlet and outlet lines from the sensor
housing.
IT IS ADVISABLE TO KEEP A LOW PPM GAS FLOWING THROUGH THE SENSOR
HOUSING WHILE THE SENSOR IS BEING REPLACED. IT IS IMPORTANT THAT WHEN A
NEW SENSOR IS INSTALLED, THE TIME BETWEEN WHEN IT WAS UNPACKED AND
FIRST EXPOSED TO CALIBRATION GAS SHOULD BE KEPT TO AN ABSOLUTE MINIMUM.
THEREFORE, THE AMOUNT OF TIME TAKEN IS A FUNCTION OF HOW LONG THE
SENSOR WAS EXPOSED TO AIR DURING REPLACEMENT. WHEN A NEW SENSOR IS
INSTALLED, IT MAY TAKE APPROXIMATELY ONE HOUR TO REACH EQUILIBRIUM ON A
CALIBRATION GAS.
2. At the base of the sensor housing are four hex screws. Remove the screws and then carefully
separate the two halves of the sensor housing.
WHEN SEPARATING THE TWO HALVES OF THE SENSOR,
NEVER TWIST THE TWO AS THIS WILL CAUSE DAMAGE
TO THE SPRING LOADED PINS. BE CAREFUL NOT TO
BEND THESE PINS WHEN THE SENSOR HALVES ARE
APART.
3. Remove the old sensor from the bottom half of the sensor housing.
THE SENSOR CONTAIN A SMALL AMOUNT OF CAUSTIC
ELECTROLYTE. WHEN DISCARDING SPENT SENSORS, CARE
SHOULD BE GIVEN NOT TO PUNCTURE THE SENSOR OR
TAKE IT APART. DISCARD THE SENSOR ACCORDING TO
LOCAL STATE OR COUNTY GUIDELINES.
4. Remove the existing O ring and examine the grooves in the inner and outer halves of the sensor
housing to be sure they are clean. Replace the O ring with the new one supplied with the
sensor.
5. Remove the new sensor from its package. Before installing it in the outer section (the one
containing the gas fittings), REMOVE THE CAP and then install the sensor with the two gold
rings facing towards the sensor half that contains the spring loaded pins.
6. Take the two halves of the sensor housing and align them so the socket head screws can be
reinstalled. Hand tighten the socket head screws being careful to do so evenly.
7. Reconnect the gas lines and begin processing gas through the sensor housing.
8. Calibrate the analyzer according to Section 5.0.
The Series 3520 Portable Trace Oxygen Analyzer is equipped with isolation valves on the inlet and
outlet of the sensor housing. When the analyzer is not in use, these valves must be kept in the closed
position (valve handle positioned perpendicular to the valve body). Prior to shutting down the analyzer
it is strongly advised that the gas trapped within the sensor housing have an oxygen concentration
less than the full range of the instrument. For instance, if the full range of the analyzer is 1,000 ppm,
prior to shutting down the analyzer (includes closing the isolation valves), the oxygen concentration
displayed on the meter should be less than 1,000 ppm. By doing this, the life of the trace oxygen
sensor will be greatly extended and the overall performance of the Series 3520 Portable Trace
Oxygen Analyzer will be enhanced.
January 1, 1995
Date
NotesOxygen sensors are sealed, contain protective coverings and in normal
conditions do not present a health hazard.
Information applies to electrolyte unless otherwise noted.
10.2 Specific Generic Ingredients
Carcinogens at levels >0.1%None
Others at levels > 1.0%Potassium Hydroxide, Lead
CAS NumberPotassium Hydroxide = KOH 1310-58-3, Lead = Pb 7439-92-1
Chemical (Synonym) and
Potassium Hydroxide (KOH) – Base, Lead (Pb) – Metal
Family
10.3 General Requirements
UsePotassium Hydroxide - electrolyte, Lead - anode
Handling
Rubber or latex gloves, safety glasses
StorageIndefinitely
10.4 Physical Properties
Boiling Point Range
Melting Point Range
Freezing Point
100 to 115 C
KOH -10 to 0 C, Lead 327 C
-40 to 0 C
Molecular WeightKOH = 56, Lead = 207
Specific Gravity
1.09 @ 20 C
Vapor PressureNot applicable
Vapor DensityNot applicable
pH > 14
Solubility in H2OComplete
% Volatiles by VolumeNone
Evaporation RateSimilar to water
Appearance and OdorColorless, odorless aqueous solution
Sensor is packaged in a sealed plastic bag, check the sensor inside for electrolyte
leakage.
If the sensor leaks inside the plastic bag or inside an analyzer sensor housing do
not remove it without rubber or latex gloves and safety glasses and a source of
water.
Flush or wipe all surfaces repeatedly with water or wet paper towel (fresh each
time).
Waste Disposal
In accordance with federal, state and local regulations
Method
10.8 Health Hazard Information
Primary Route(s) of
Ingestion, eye and skin contact
Entry
Exposure LimitsPotassium Hydroxide - ACGIH TLV 2 mg/cubic meter; Lead - OSHA PEL .05
mg/cubic meter
IngestionElectrolyte could be harmful or fatal if swallowed. Oral LD50 (RAT) = 2433 mg/kg
EyeElectrolyte is corrosive and eye contact could result in permanent loss of vision.
SkinElectrolyte is corrosive and skin contact could result in a chemical burn.
InhalationLiquid inhalation is unlikely.
Symptoms
Other Lead is listed by some states as a chemical known to cause birth defects or other
reproductive harm.
10.8 Health Hazard Information
Primary Route(s) of
Ingestion, eye and skin contact
Entry
Exposure LimitsPotassium Hydroxide - ACGIH TLV 2 mg/cubic meter; Lead - OSHA PEL .05
mg/cubic meter
IngestionElectrolyte could be harmful or fatal if swallowed. Oral LD50 (RAT) = 2433 mg/kg
EyeElectrolyte is corrosive and eye contact could result in permanent loss of vision.
SkinElectrolyte is corrosive and skin contact could result in a chemical burn.
InhalationLiquid inhalation is unlikely.
Symptoms
Eye contact - burning sensation.
Skin contact - soapy slick feeling.
Medical Conditions
None
Aggravated
Carcinogenic
Reference Data
NTP Annual Report on Carcinogens - not listed
LARC Monographs - not listed
OSHA - not listed
Other Lead is listed by some states as a chemical known to cause birth defects or other
Recommended for "portable/trans-portable" Trace O2 Analysis applications
Spot or Intermittent Trace O2 Readings at Different Sample Tap Locations
If your analyzer has been equipped with the above option, please read below.
The “Sample Line Block & Bleed / Sensor-Isolation Gas Delivery System” option serves as a
convenient means to “PURGE” (or “BLEED”) the sample line before switching the sensor over to the
“SAMPLE” position, yet simultaneously keeping the sensor in an “Isolated” state (with a pre-purged,
low-O2 background gas atmosphere sealed inside). Upon relocation and connection to subsequent
gas samples, the Alpha Omega Instruments Trace Oxygen Analyzer is, therefore, primed-and-ready-to-go to make a trace O2 reading, because:
1. The O2 sensor is already reading and equilibrated on a low O2 sample, immediately prior to
switching over to the next gas sample.
2. At the same time, immediately prior to being switched over to the next sample, also, the
sample line is completely “pre-purged” by the next gas sample (purging out all of the previous
gas sample, and (or) any possibility of entrained air.
The “Sample Line Block & Bleed / Sensor-Isolation Gas Delivery System” option utilizes the analyzer’s
own sample conditioning components [i.e., pump, regulator, flowmeter, filter(s), etc.] to perform the
“PURGE” (bleed) operation.
Regardless of whether each gas sample is under pressure (with flow controlled by a regulator or
needle valve) or under vacuum conditions (aspirated by a sample pump or other means), Used as a
flow pre-set adjustment, and because the pressure differential across the sensor is negligible.
CAUTION: It is essential for the sensor’s longevity and performance below 100 ppm that the retained
gas inside the sensor housing after isolation is at a low trace O2 level (below the highest range of the
instrument).
1. Ensure that the Analyzer is ON, and that the “Block & Bleed / Sensor Isolation 4-way Sample
Selector Valve” is pointing toward the “BLEED / BYPASS” label (or toward the port connected to
the base of the flowmeter).
2. Connect the Sample Gas to the ¼” compression Sample Inlet Fitting on “Block & Bleed / Sensor
Isolation 4-way Sample Selector Valve.” (Note: this is the only unused port connection).
3. Using available sample pump, regulator, or other flow controls, establish the suggested 0.5 slpm
(0.2 to 1.2 slpm) sample flow.
Note: While in the “BLEED / BYPASS” position, the sample gas is re-directed from the sample inlet to
the outlet, “bypassing” the sensor. Bleed the sample line for a few seconds to a few minutes
(depending upon sample line length, any filter bowls or other “dead volumes”, etc.).
CAUTION: Before following step 4 below, both sensor isolation ball valves must be in the open
position. Not doing so may damage the oxygen sensor.
4. Switch the “Block & Bleed / Sensor Isolation Four-Way sample Selector Valve” to the
“MEASURE” position (pointing toward the sensor housing). Verify that the flow rate remains the
same.
5. After allowing enough time on the sample for a sufficiently stable O2 reading, switch back to the
“BLEED/BYPASS” position.
Note: ENSURE that the O2 reading while in the “BLEED / BYPASS” position (Bypass & Bleed /
Sensor Isolation) state is
BELOW 1,000ppm.
Otherwise, purge the sensor out IMMEDIATELY using a better purity purge gas.