IONALYSIS M
OM/2 OXYGEN MONITOR
INSTRUCTION MANUAL
CONTENTS
1. Introduction
2. Parts list
3. Principle of Measurement
4. Operation
5. Technical Data
6. Maintenance
7. Calibration
8. Repairs
1. Introduction
Features
Micro-processor controlled re-calibration for oxygen cell drift
Built-in alarm – to warn of purge loss
Re-chargeable batteries (charger included)
Milled from solid, aluminium case
No zero calibration required
Two-year oxygen cell life
Simple and economical Oxygen cell replacement
Robust carrying case
The Ionalysis Oxygen Monitor is designed specifically for the welding industry where the monitoring of purge gasses is
important. It is a micro-processor controlled, rechargeable, battery-powered portable oxygen monitoring
device. It is a highly robust device and is designed to be used in an industrial environment..
The Oxygen Monitor will measure oxygen in the range 0-25%.
NB The oxygen cell may suffer permanent damage if exposed to:-
CO2concentrations above 25%
Solvents or solvent vapours
2. Parts List.
1. Oxygen Monitor
2. Carrying case
3. Hand-bulb pump
4. Length of hose with stainless steel sampling probe
5. Battery charger
6. Manual
3. Principle of Measurement
Oxygen concentration is measured by means of a self-powered, partial pressure, metal-gas battery
type cell. It is very competitively priced, and is the only consumable component of the device.
3.1. Carrier Gas
The "Carrier Gas" is the gas in which the oxygen to be measured, exists. Typical carrier gasses are
Argon, helium, nitrogen etc. The Oxygen Monitor is tolerant to all carrier gasses (except CO2- see Section 1.)
and will give a correct reading for oxygen percentage regardless of carrier gas.
3.2. Affects of temperature on oxygen cell output
As the output from the oxygen cell will vary with temperature, there is electronic temperature
compensation built into the oxygen cell.
3.3. Affects of pressure on oxygen cell output
As the oxygen cell is of the partial pressure type, the output (and therefore the percentage oxygen
displayed), will vary with atmospheric pressure. This variation will have negligible effect at low concentrations
of oxygen, nevertheless it is as well to re-set to 20.9% whenever the displayed reading in atmosphere is
significantly different. See Section 7 - Calibration.
4. Operation.
When first switching o, the monitor will display the previously set alarm level.
If 0.0 is displayed the alarm is disabled, and the monitor will then display the oxygen percentage.
If a value other than 0.0 is displayed, the alarm is enabled and the figure displayed is the alarm level.
4.1 Sampling the purge gas
There are two ways of sampling the purge:-
Flowing the exhaust from the job directly through the sample chamber
This is the best way, as you can then easily use the alarm facility to warn of purge loss, but beware, don’t
allow the situation where the tube to the monitor is the only means of escape for the purge gas - if this is
allowed to happen then the butt may become pressurized. Instead, if there is only one exhaust from the job,
put a “T” piece between the job and the monitor to allow any excess gas to vent to atmosphere.
Using the hand-bulb pump and capillary to sample the purge gas
This method is particularly useful for quick spot checks, or if the only access to the purge gas is via an open
butt, ie. tie-in welds. But don’t pump too hard or you may pump faster than the flow rate from the job and pull
in oxygen from the atmosphere, thereby getting an invalid reading.
4.2. The Alarm
The alarm, if enabled, works in the following way:-
1. When the oxygen level of the purge gas drops below the alarm level for the first time, the alarm will
sound continuously as long as the oxygen level remains below the alarm level.
2. Once you’re happy with the purge, press the “ON/OFF” button. This will kill the alarm and switch the
monitor into its second mode of operation. In this mode the alarm will not sound whilst the oxygen level
remains below the alarm level set, the alarm will only sound if the oxygen level rises above the alarm level
set. The monitor will now remain in this mode until it is switched off.
4.2.1. Enabling the alarm and setting the alarm level
1. With the “SET” button held down, press the “ON/OFF” button
The monitor will display “A0”
2. Press the “SET” button until the desired level is reached.
3. Press the “ON/OFF/ button
The monitor will now display the oxygen level and is ready for use.
4.3. Low Battery.
The Oxygen Monitor continuously checks its battery charge level. When the batteries are nearing exhaustion
“LO BAT” will be displayed. You can still use the Oxygen Monitor even though the battery level is getting
low - the Oxygen Monitor will continue to operate for approx. 1 hour after the low battery warning is given.
NB The Oxygen Monitor should not be re-charged before the low-battery
warning is displayed. If it is, battery life will be impaired
4.4. Re-charging.
Ensure that the Oxygen Monitor is switched off - plug the supplied charger into a 240v
outlet and connect to the Oxygen Monitor. A full charge can be achieved overnight.
NB The Oxygen Monitor should not be left on charge for more than 16 hours
or battery life will be impaired.
5. Technical Data
5.1. Oxygen Monitor
Nominal range 0.0% - 25%
Response time < 60 seconds to 0.1%
Accuracy Better than ±2% Full Scale
Cell operating life 24 months
Temperature range 0 - 40oC
Pressure range 0.9 - 1.1 Atmospheres
Operating humidity 0-99% RH (non-condensing)
Drift < 2% signal/month
Typically < 5% over operating life
Battery life Under average operating conditions – 2-3
weeks on a single charge.
Dimensions (incl. case) 160mm x 90mm x 50mm
Weight 0.5Kg
5.2. Battery Charger
Constant current type with thermal fuse protection.
Voltage 240 A/C
Output 85 ma
Dimensions 85mm x 60mm x 50mm (ex. pins)
6. Maintenance.
The only maintenance which the user should attempt is the replacement of a spent oxygen cell.
6.1. Replacement of Oxygen Cell.
1. Remove the oxygen monitor from its carrying case.
2. Remove the four screws which hold the case together and split the case.
3. Push the blade of a small instrument driver between the three-pin connector and the locking tab on the
oxygen cell.
4. Carefully dis-connect the oxygen cell.
5. Unscrew the oxygen cell.
6. Dispose of the spent oxygen cell.
7. Firmly screw home a new cell and re-connect.
8. If you removed the battery lead, it must be replaced correctly – black wire nearest to the edge of the PCB.
9. Replace and tighten the four screws which hold the case together.
10. The Oxygen Monitor must be re-set for atmospheric oxygen level after fitting a new
cell.
7. Calibration.
7.1. Zero adjustment.
The
Oxygen Monitor is zeroed during commissioning and will need no further calibration with respect to zero. However,
it is advisable to periodically check the device.
1.
Place the sample tube in such a position as to ensure a "good" sample.
2.
Provide the Oxygen Monitor with a supply of high purity argon.
3.
Switch on and draw a sample.
4.
Ensure that the display reads < 0.2% within 1 minute.
If
you cannot get a reading of < 0.2%, contact Ionalysis for advice.
7.2. Re-setting the monitor to the atmospheric oxygen level.
Re-
setting is only necessary as follows:-
1.
When a fresh oxygen cell has been fitted
or:-
2. When the oxygen reading is significantly adrift from 20.9% in atmosphere.
To re-set the monitor to atmospheric oxygen level.
First, draw air into the sample chamber, allow the oxygen reading to stabilise then press the “SET” button.
7.3 Errors.
If the monitor displays “LO” whilst you are trying to set the monitor to the atmospheric oxygen level, this
indicates that the oxygen cell is exhausted and should be replaced.
7.4. Checking oxygen calibration
If you wish to check that the Oxygen Monitor is displaying the correct oxygen percentage at a level other
than ambient or zero, you will need a supply of argon with a known oxygen concentration of about, say, 0.5%. The
Oxygen Monitor should be allowed to sample this gas for a full 5 minutes. Its accuracy can then be verified.
8. Repairs.
You
are strongly advised not to attempt to carry out any repairs on the Oxygen Monitor. Repairs will be dealt with on the
highest priority; any instrument returned for repair can be expected to be returned within one week of receipt.
Ionalysis Ltd., 44, Wyngate Road, Cheadle Hulme, Cheshire. SK8 6ES.
TEL. 0161-486 1691
FAX. 0161-486 9420
Web: ionalysis.co.uk
IONALYSIS LIMITED
M
Oxygen Monitor – OM/2 –Alarm System
Using the Alarm
There are two modes of operation, they are pre-set:-
-Mode 1, where the alarm only sounds below the alarm level set,
and
-Mode 2, where the alarm only sounds above the alarm level set.
The alarm works in the following way. First of all, it sounds
when the desired purge level has been reached ie. the job is
purged (Mode 1). Then, after the operator indicates to the
monitor that he has seen that the purge has been reached, the
monitor then warns of purge loss (Mode 2).
Operation
1. Switch the monitor on and set the required alarm level (see
the back label of the monitor), the monitor is now in Mode 1
2. Connect the monitor to the system exhaust
3. When the oxygen level of the purge gas drops below the alarm
level, the alarm will sound continuously as long as the oxygen
level remains below the alarm level.
4. Once you’re happy with the purge, press the “ON/OFF” button.
This will kill the alarm and switch the monitor into Mode 2
operation. In this mode the alarm will not sound whilst the
oxygen level remains below the alarm level set, the alarm will
only sound if the oxygen level rises above the alarm level
set. The monitor will now remain in this mode until it is
switched off.
To conclude, every time you switch the monitor on, it is in Mode
1, and, in this mode, if you press the ON/OFF button whilst
the alarm is sounding, it drops into Mode 2.
If the monitor is in Mode 2 and you want the monitor to be in
Mode 1, you must switch the monitor off, then back on again.
IONALYSIS LIMITED
M
Oxygen Monitor – OM/2
Sampling the Backing Purge
General
Don’t allow solvent fumes to enter the sample chamber as the oxygen
sensor (which is immediately behind the chamber) will be damaged by
them.
When inserting or removing the tube connectors from the sample ports
a slight twist will ease the connector home.
To conserve battery life, switch the monitor off after use.
Setting the atmospheric oxygen level displayed
The atmospheric concentration of oxygen is 20.9%, but the OM/2 won’t always display 20.9% when
monitoring the atmosphere.
The OM/2 is affected by atmospheric pressure – the higher the pressure
the higher the figure displayed.
To adjust the figure displayed to 20.9%
1. Make sure that the sample chamber has air in it – no purge gas
residue.
2. Press the “SET” button
Sampling the purge gas
There are two ways of sampling the purge:-
Flowing the exhaust from the job directly through the sample chamber
This is the best way, as you can then easily use the alarm facility to
warn of purge loss, but beware, don’t allow the situation where
the tube to the monitor is the only means of escape for the purge
gas - if this is allowed to happen then the butt may become
pressurized. Instead, if there is only one exhaust from the job,
put a “T” piece between the job and the monitor to allow any excess
gas to vent to atmosphere.
Using the hand-bulb pump and capillary to sample the purge gas
This method is particularly useful for quick spot checks, or if the only access to the purge gas is via an
open butt, ie. tie-in welds. But don’t pump too hard or you may pump faster than the flow rate from
the job and pull in oxygen from the atmosphere, thereby getting an invalid reading.
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