Personal Multigas
Tel: +44 (0)191 490 1547
Fax: +44 (0)191 477 5371
Email: northernsales@thorneandderrick.co.uk
Website: www.heattracing.co.uk
User Manual
May 2010
Issue 10
Safety information:
• Read and understand all instructions in the
operation section of this manual before use.
• Do not substitute components as this may
impair intrinsic safety and invalidate warranty.
• Observe all warnings and instructions marked
on the unit and within this manual.
• Observe site health and safety procedures for
gases being monitored and evacuation procedures.
• Make sure you understand the screen display
and alarm warnings.
• If this product is not working properly, read the
troubleshooting guide or call Crowcon.
• Ensure qualified service personnel change sensors and operating system.
• Ensure maintenance and calibration are carried out in accordance with the procedures in the
Instructions specific for use in hazardous areas
The following instructions apply to equipment covered by certificate number:
The following information covers all relevant points listed in clause 1.0.6 of the EHSR’s of the ATEX directive.
1. The certification marking is as follows:
(-4°F to +131°F). The equipment should not be
used outside these ranges.
Compliance with the Essential Health and Safety
Requirements has been assured by
compliance with EN50014:1997 + Amds 1 & 2,
EN50020:2002 and EN50018:2000, as certified by Baseefa. Compliance with gas detection performance standards EN50054, EN50057,
EN61779-1, EN61779-4, EN50104 and EN50270
has been certified by Lloyd’s Register.
Repair of this equipment and gas sensor replacement shall be carried out by the manufacturer or
in accordance with the applicable code of practice.
If the equipment is likely to come into contact
with aggressive substances, then it is the responsibility of the user to take suitable precautions
that prevent it from being adversely affected, thus
ensuring that the type of protection is not compromised.
The rechargeable battery must only be charged in
non-hazardous (safe) areas by connection to the
specified Crowcon charger power supply.
Only the following cell types may be fitted in the
battery compartment of the non-rechargeable
battery pack:
Duracell MN1500 LR6
Varta 4006
Ever Ready Energizer LR6
GP Batteries 15A LR6 1.5V
The cells must only be changed in a non-hazardous (safe) area.
The equipment is not certified for use in atmospheres containing more than 21% oxygen.
Area Classifications: Zone 1: An area classified as Zone 1 is likely to have
ignitable concentrations of flammable gases,
vapours or liquids present under normal operating conditions.
Zone 2: An area classified as Zone 2 is not likely to
have ignitable concentrations of flammable
gases, vapours or liquids present under normal operating conditions.
2. The equipment may be used in zones 1 and 2 with
group IIA, IIB, and IIC flammable gases, temperature classes and vapours T1, T2, T3 and T4 with
rechargeable battery option and classes T1, T2
and T3 with non-rechargeable battery option.
3. The equipment is certified for use in ambient temperatures in the range –20°C to +55°C
Crowcon Detection Instruments Ltd
2 Blacklands Way, Abingdon
Tel. +44 (0)1235 557700
Fax. +44 (0)1235 557749
Email: sales@crowcon.com
© Copyright Crowcon Detection Instruments Ltd 2010.
All rights are reserved. No part of the document may be
photocopied, reproduced, or translated to another language
without the prior written consent of Crowcon Detection
Instruments Ltd.
Publication number: M07237
Tenth edition: May 2010
Personal Multigas Monitor
Quickstart guide.........................................2
I. Introduction.............................................6
II. Operation...............................................8
III. Batteries...............................................12
IV. Alarm indications.................................14
V. Fixing accessories..................................15
VI. Flow sampling.....................................16
VII. Maintenance and calibration...............21
VIII. PC interface and software..................23
IX. i-module replacement..........................24
X. Specification.........................................26
XI. Accessories and spare parts.................27
XII. Troubleshooting guide........................29
Appendix: Limitations of sensors...............30
Personal Multigas Monitor
Thank you for purchasing the new Tetra Personal Multigas Monitor. Tetra has
redefined portable gas monitoring and will give you years of unparalleled service and reliability.
Please read the instructions carefully before use. Keep the manual for future
Remove the Tetra Personal Multigas Monitor from the packaging. The Tetra
accessories will be located in the bottom of the box. Check the contents are
complete, you should have:
• Tetra unit;
• Optional battery charger power supply for units supplied with
rechargeable Li-ion batteries;
• A configuration report detailing the sensors installed, alarm
settings and a calibration certificate;
• Optional accessories such as flow adaptor and aspirator bulb;
• Optional spare battery pack for non-rechargeable units.
Battery check
The Tetra Personal Multigas Monitor has two battery options: Li-ion rechargeable or alkaline non-rechargeable batteries. Depending on the battery option
chosen, the Tetra will operate for a minimum of 12 hours and up to 18 hours
when fully charged.
Rechargeable units
Tetra uses a Li-ion battery pack and should arrive with sufficient charge so that
the unit can be used straight out of the box. However, if this is the first time
you have used the Tetra unit, you may need to charge the batteries to attain
the full 12 to 14.5 hour operating time. (The actual operating time will depend
on the types of sensors installed.)
Warning: rechargeable units
Do not attempt to use any other charger power supply with this unit except
the one supplied by Crowcon. Failure to comply could invalidate safety certification and may result in permanent damage to the unit.
Quickstart guide
Quickstart guide
1. Getting started
Review your Tetra unit
Top view
Alarm LEDs
IR comms
Operator LCD
display screen
Side view
Belt clip
Front plate
Switching on your unit
Tetra requires little setting up, follow these simple steps to get your unit ready
for use.
1. Ensure the unit is in clean air.
2. Switch on
Press and hold the operator
button until the red LED
The operator display screen
will light up and the unit will
begin a warm up sequence.
Quickstart guide
Tetra warm up sequence
a) The unit will test the
alarm LEDs, sounder,
vibration alerts, and
the operator display
screen. The sounder
may be silenced by
pressing the button.
LEDs Alarm test
Sounder Alarm test
Vibrator Alarm test
b) The unit will continue through a warm up sequence as shown below,
this will take approximately 45 seconds.
vs. 1.01
Gas Detection You ..
1-2 m
Click to
7 secs
c) Auto zero
If auto zero is enabled (default), the unit will display the auto zero
menu. Press the operator button with a single click to confirm auto
zero. If the operator button is not pressed within the 10 second time
out, Tetra will proceed directly to Run mode without performing zero.
Auto zero
Click to
7 secs
No auto zero
Run mode
In the event of an alarm
Run mode
Your unit is now ready to use.
Below is a typical screen display showing the
unit in normal gas monitoring Run mode.
Screen Icons
Warm up
Familiarise yourself with the gases being
monitored in your unit and make sure you
understand site health and safety procedures
in the event of alarm conditions.
Tetra units with an inbuilt pump will produce
a low humming noise, this is normal.
icon, Tetra
Auto zero
Confidence signals
In normal Run mode, Tetra will emit a short beep every 10 seconds and the
OK icon flashes to show operational health.
2. In the event of an alarm
Alarm signals
In the event of gas concentrations exceeding the alarm thresholds for any gas
being monitored, Tetra will activate the alarm signals.
Alarm signals
Alarm icon
The red and blue
alarm LEDs will
flash, the sounder
will emit a loud,
ppm 2
fast series of beeps,
the internal vibrator
alarm will activate.
ppm O2
The operator screen
will display the gas in
alarm and the alarm
level. See the figure
Gas example
to the left.
under alarm
Switching off
1. When the gas level returns to normal, press the operator button. This
will reset your Tetra unit to normal Run mode. If gas levels are still in
alarm, the button will have no effect.
The Tetra alarm is set to latch by default.
The unit will still continue in alarm mode
even when gas levels return to normal,
until the alarm is cleared, by pressing the
operator button.
For any one gas, there
are normally two alarm
thresholds. These are
indicated by the alarm
icons shown.
1 2
3. Switch off unit and storage
Switching off unit
1. Press and hold the button for 5 seconds. The shut down menu
appears, continue to hold button until the unit counts down to shut
4 sec
Storing conditions
In order to optimise sensor performance and lifetime, your Tetra unit should
be stored in a safe, non-hazardous area, 0-30°C, 10-90%RH.
4. Additional information
battery recharging information go to section III.
fixing accessories go to section V.
sampling section go to section VI.
calibration information go to section VII.
troubleshooting guide go to section XII.
I. Introduction
Thank you for purchasing the new Tetra Personal Multigas Monitor. Tetra is a
portable multigas detector, designed to be carried or worn by individuals working in hazardous environments such as confined spaces. It is suitable for use
in Zone 1 and 2 hazardous areas. Tetra can monitor up to four different gases
and display the readings simultaneously on a display screen. Alarm warnings are
given through a combination of a loud audible alarm, a bright visual alarm of
blue/red flashing LEDs and an internal vibrator. Tetra can be fitted with a wide
range of modular, plug and play gas sensors. Each sensor carries an intelligent
processor which contains calibration and sensor information.
Tetra is battery operated and is available with rechargeable and non-rechargeable battery options. The rechargeable unit contains its own internal charger, a
battery charger power supply is available for 110 V or 230 V a.c. see section XI
for more information.
At Crowcon we recognised the need for a reliable and robust confined space
personal monitoring system, which is lightweight, compact, easy to use and
cost effective. Tetra has a single operator button, and an intelligent user-friendly
display with automatic backlight. Gas levels are continuously monitored providing normal gas readings, peak readings and time weighted averages (TWA).
Tetra is available as a diffusion sampling instrument or with built in electric
sampling pump. Configuration and data/event logging is handled by Crowcon
Portables PC software, the PC communication link being provided through a
fast, reliable optical link.
Tetra’s shape and design makes it comfortable to wear and as non-intrusive
as possible, with a non-slip grip for better handling. Extra accessories, such as
shoulder strap and chest harness, can be purchased.
Tetra has been designed from top to bottom to bring you a revolution in ease
of use, maintenance and extreme reliability. Through innovative and rigorous
design technology, we have introduced several new features.
i-module gas sensor
Tetra uses unique plug and play i-module sensor technology. Each sensor unit
incorporates its own intelligent processor holding sensor configuration and
calibration data. Different sensors can be purchased, and once inserted, are
immediately ready to run. Tetra can operate with up to four sensors and display, simultaneously, information and gas readings for all the sensors on one
screen. This means no redundancy and assured future investment in your Tetra
unit, allowing you to swap sensors between units or configure your unit, as
appropriate, to your current needs. Plug and play will ease maintenance time
and cost, and the intelligent modular system will remove the need to calibrate
each sensor. Additional i-modules can be purchased pre-calibrated from your
local supplier.
Reliable, anti-shock mechanics and robust housing
The Tetra housing is built from resilient material, giving it strength and flexibility
to withstand the hardest of working conditions, water and dust tight to IP65,
and with a non-slip grip. The internal structure has been carefully designed to
make servicing easy and at the same time very rugged. If the unit is dropped,
there will be no disruption of power or function, ensuring reliability and service
for years to come.
The internal software in Tetra has been designed and written in accordance
with the requirement of IEC 61508 to ensure quality and integrity of operation.
Tetra has been designed to give a truly reliable personal gas monitoring system.
The internal circuitry includes an external watchdog, the software monitors for
any malfunction within the unit and will display an error warning to the user
should they occur.
II. Operation
2.1 Switch-on sequence
1. Ensure the unit is in clean air.
2. Switch on
Press and hold the operator button until the red LED flashes.
The instrument begins with testing all the LCD segments on the
operator display screen, the red and blue alarm LEDs, sounder and
internal vibrator alert for about 5 seconds. The sounder may be
silenced by pressing the button. The unit enters a warm up mode and
displays a sequence of screens, see page 3 for more details. At the end
of warm up, the auto zero menu will be displayed.
The auto zero function can be disabled or set
to run automatically, without user confirmation:
autozero menu will not appear. See section VIII
PC Interface and software.
Battery check
Use this time to
check there is sufficient
charge in the battery pack
NB. During the warm up sequence, the date for next calibration will be
displayed. If the date has expired or has passed, the Tetra unit will display a
warning message that calibration is due. The instrument can still function, but
it is strongly recommended the unit is sent for calibration as soon as possible.
Tetra can be set, using the Portables PC software, for the instrument to
shut down automatically, if the calibration date is passed, to prevent further
operation of the instrument.
3. Auto zero menu
Press the operator button with a single click to confirm auto zero.
If the operator button is not pressed within 10 seconds, Tetra will
proceed directly to Run mode without performing a zero. Flammable
and toxic sensors will be set to read zero and the oxygen sensor to
read 20.9%.
NB. If auto zero fails, a warning message will be displayed
and an ‘X’ will appear against the sensor that has failed.
Switch off
To switch off the unit, press and hold the operator button for 5
seconds. A shut-down message ‘OFF IN’ will appear, continue to hold
button until the unit counts down to shut off.
Run mode
2.2 Run mode
The Tetra unit will display up to four gas readings simultaneously on the operator display screen. A typical display
with four sensors installed, is shown below.
Screen Icons
Warm up
icon, Tetra
Each channel will display the gas name, units and current
value. Familiarise yourself with the gases currently being
monitored in your unit. Ensure you understand site health
and safety procedures. For information on peak and TWA
readings, go to section 2.4.
Auto zero
Confidence signals
To reassure users the unit is working correctly, the Tetra unit
will emit a short beep every 10 seconds and the OK icon
will flash. The pump is running correctly when the icon is
2.3 Display symbol guide
A full battery is represented by a battery icon showing a full
six bars. A low battery charge will show 1 to 2 bars. When
zero bars are shown the battery icon flashes. The sounder
will emit warning bleeps.
If the battery becomes too low, Tetra will display a ‘Battery
low’ warning message and switch off.
Internal pump
This revolving icon indicates the internal pump is running. If
the pump or airway becomes blocked, the unit will emit a
warning sound and display a warning message. Check the
flow adaptor and sample lines are free from dirt or water,
and that the sample line is not kinked or blocked. Restart
pump by pressing the operator button.
Display options
TWA alarm
Tetra will display the TWA alarm when the 15 minute or 8
hour time weighted average alarm threshold is passed for
toxic gases.
2.4 Display options
Tetra provides two additional selectable displays:
Peak display
When Peak mode is selected the instrument shows the highest value
for flammable and toxic gases and the lowest value for oxygen since
the mode was selected. This is useful for vertical entry checks where
the whole instrument can be lowered down the shaft rather than just a
sampling tube. Deselecting Peak mode clears stored peak information.
TWA display
Shows the 15 minute or 8 hour time weighted average (TWA), for
toxic gases, monitored since last turn on.
1. To view the additional display option menu, double-click the operator
Gas 0
0.0 TWA20.8
2. Press the operator button with a single click to scroll through the list.
When your choice is highlighted, double-click the operator button.
Peak display
1. Scroll
2. Select
Peak 0
The Tetra operator screen will display the peak or TWA icon and the
gas readings recorded.
Peak test
When performing a peak test, such as a vertical entry check, previous
readings can be cleared on entry to the peak display option.
The Tetra instrument can perform an autozero by selecting the Zero
function from the menu. When zero is completed, the instrument will
return to normal operation.
2.5 Logging
Tetra incorporates data and event logging which can be accessed using the IR
communications link with Portables PC software (See section VIII). It can record
data each minute for 50 hours up to a limit of 1500 events.
Tetra records the time and date for a number of operating and diagnostic
events including:
• Switch on and switch off
• Level 1, Level 2 and Time Weighted Average Alarms, alarm on,
alarm off and the peak level during the alarm
• Zero, calibration and gas test with success or failure
• Pellistor saver on and off
• The battery condition is logged every 15 minutes while the
instrument is operating, and certain configuration changes are
also logged.
III. Batteries
3.1 Rechargeable batteries
Recharge time for the Li-ion batteries is less then 6 hours (less, if they are not
fully discharged). Rechargeable batteries will typically last 12+ hours, fully
loaded with 3 or 4 sensors and a pump.
Charging the batteries
1. Ensure you are in a safe area.
2. Plug the charger power supply into a mains socket.
3. The charging socket is located on the bottom of the unit: there is
a small cover which can be opened to reveal the socket, (see figure
below). Pull back the cover and insert the lead into the socket.
Switch on the power.
The unit would normally be left switched off for charging and will
display a battery icon on the display sweeping from empty to full.
When charging is complete a full battery icon flashes on the screen. If
the unit is switched on during charge the normal display battery icon
sweeps from empty to full. On disconnecting the charger power supply
this display icon will update in 20 seconds to show actual charge state.
The unit is fully charged when the charging battery icon is flashing (see
Battery fully charged
Tetra warning message
Battery full
Low battery
25 Battery needs
The charging time will be longer if the unit is switched on during charging.
example). In Run mode, the battery icon will display six bars when it is
4. Remove the lead from the charging socket and replace the protective
3.2 Non-rechargeable batteries
Tetra uses a three AA alkaline battery pack which will give 11 hours operating
time. The following battery types are suitable for the non-rechargeable version:
Energizer type LR6 MN1500
Gold Peak type 15A LR6
Duracell type MN1500 LR6
Varta type 4006
Alkaline batteries will typically last 11 hours.
To replace the battery pack, ensure you are in a safe, non-hazardous area. The
battery pack is located in the bottom of the instrument. Remove the access
cover and withdraw the battery pack. Replace the 3 x AA cells, then reinsert the
pack into the instrument and replace and securely fasten the access cover.
Alarm indications
IV. Alarm indications
Tetra provides two instantaneous alarm levels for each installed sensor, designated level 1 and level 2. For toxic gas sensors, there are also two time
weighted average alarms (TWA), one for short term exposure (STEL): based on
a 15 minute time weighted average, and the second TWA alarm is for long term
exposure: based on a 8 hour time weighted average.
Alarm configurations are set via the Crowcon Portables PC software.
The following settings can be made:
Alarm thresholds for each sensor: Level 1
and level 2 alarms can be set for each individual 1 2
gas sensor.
Alarm type: This can be set to rising levels of gas concentration, or as falling. Oxygen sensors are set to falling for
deficiency monitoring.
Alarm latching: Alarms can be set to be latched or
unlatched. Latched alarms will require the operator button to
be pushed in order to clear the alarm. This is the default setting. Unlatched alarms will clear automatically when the gas
hazard has passed.
Alarm mute: The sounder can be set to mute for level 1
alarm only; pressing the operator button during an alarm
condition ie presence of hazardous gas, will silence the
sounder and stop the vibration alarm. The alarm LEDs will
continue to flash.
Alarm sounder tone: Different tones can be selected to
achieve the best performance for the monitoring conditions
In the event of a Time Weighted Alarm (TWA)
In the event the 15 minute or the 8 hour TWA is triggered,
Tetra will go into alarm and display the TWA icon with the
toxic gas readings. The 8 hour TWA alarm cannot be cleared.
Fixing accessories
V. Fixing Accessories
Belt clip
Tetra has a strong built-in belt clip located on the back of the unit. Lifting the
small lever will allow the unit to be attached to a belt more easily.
Universal harness plate
Crowcon provide a universal harness plate which can be used with either a
chest harness or a shoulder strap.
Belt clip
Universal harness plate
How to wear your Tetra unit
Chest harness
Slide the universal harness plate over the belt clip at the back of your Tetra unit.
The plate will lock automatically into place. Create a chest harness by attaching
one strap to the top connectors, to go around the neck, and the other to link
around the waist using the side connectors. Adjust the lengths until the Tetra
unit is in a comfortable working position.
Shoulder strap
With the universal harness plate in place on the belt clip, attach the shoulder
strap accessory onto the top connectors. Adjust to a comfortable working
See accessories, section XI, for full list.
Flow sampling
VI. Flow sampling
Attaching the flow adaptor plate
To perform manual sampling using Tetra, a flow adaptor plate must be fitted
onto the front of the instrument.
Flow adaptor
Gas in
Gas out
1. To fit the flow adaptor plate, slide the top of the flow adaptor
plate into the small recess on the front of the instrument, screw the
thumbscrew until the plate is tightly fitted into place.
2. Attach the sampling tube or flow accessory onto the gas inlet nozzle.
3. Non- Pumped (diffusion) instruments
Attach the aspirator bulb onto the gas outlet nozzle.
4. To remove the flow adaptor plate, unscrew the thumbscrew and lift
the plate away from the instrument.
The sampling tube supplied is normally a 2m (6ft) length. Longer lengths of sampling
tube can be provided, but will increase the time taken to get a sample from the point
of sampling to the Tetra instrument. When using an extended length of tubing a
response time test is recommended. Gas of known concentration should be sampled
along the full length of tubing to be used and the time taken for the sensor reading to
reach the known gas levels should be noted. This time should be used as the minimum
for sampling before readings should be taken.
Flow sampling
Pumped instruments
Tetra’s inbuilt pump draws sample air in through the inlet nozzle of the flow
adaptor plate and out through the outlet nozzle. When using sampling equipment, if the inlet should become blocked with dirt, water or a kink in the line,
the pump will automatically stop. Tetra will emit a rapid series of beeps and
display a warning message. To restart the pump, clear the blockage and press
the operator button.
Extension probes, drop lines
and water traps are available.
See accessories section XI.
Diffusion instruments
When using the manual aspirator kit, adopt a consistent style whilst using the
hand aspirator. Crowcon recommend squeezing once per second to achieve a
flow rate of approximately 0.5 - 1 litre/min. At least 10 pumps per sample are
Gas testing
Tetra gas test accessory kit
The Gas Test Accessory is a gas testing kit designed to enable gas testing of the
Tetra multigas detector using a specially formulated, high stability long life quad
gas mix. It can be used with Tetra units having sensors for Flammable, Oxygen,
Carbon Monoxide and Hydrogen Sulphide gases, and all Tetra units with these
sensors can be gas tested using the kit.
6.1 Gas testing
Gas testing checks the sensor is responding within set limits to an applied gas
of known composition. This can be performed as often as desired, but would
usually be carried out each time the Tetra is issued for use. The Tetra itself will
determine Pass/Fail status for the gas test.
In order to perform successful gas tests ensure:
• The quad gas mixture used has the correct gas concentration, and that
it is within the validity date specified by the supplier.
• The gas flow path is leak tight. It is important to check that the flow
plate is properly fitted to the Tetra, and the outlet tubing is not restricted in any way, nor additional tubing length used.
The Gas Test Accessory Kit is supplied in a convenient carry case and comprises;
a gas cylinder containing the quad gas mix, a 'Trigger' regulator with interconnect tubing, a magnet - used to activate Test mode, an aspirator plate to attach
to the Tetra and a vent line. The Trigger regulator can be operated in two ways:
(1) squeeze and hold - allows gas flow as long as the lever is held in, or (2) by
lifting the lever - the flow is locked on. There are two versions of the kit; one
for pumped Tetra units and one for non-pumped Tetra units supplied with an
aspirator plate. Pumped Tetra units require the use of the plate with the integral
bellows assembly.
6.2 How to perform a gas test
1. Ensure your Tetra unit is switched on and in normal operation.
2. Clip the flow plate onto the front of the unit and attach the hose from
the Trigger regulator.
Attach the outlet hose to ‘vent gas away’ - do not extend this hose
and do not restrict or allow kinks.
3. Swipe the magnet past the display adjacent to the LED lens. Your Tetra
unit will activate the Gas Test and show ‘GAS TEST’ on the display.
4. Tetra will display a progress bar at the bottom, the names of the gas
Field calibration
sensors fitted are shown with a cross beside each.
Operate the Trigger regulator and apply gas to the Tetra whilst the
progress bar is counting down.
As gas flows and the sensors respond, the Tetra monitors the response
against stored gas values. Provided the response reaches a predefined
window around each gas value within the test time the cross by each
sensor will change to a tick and the unit passes the test.
If any sensor response fails the test the Tetra will display a message
advising the unit be sent for calibration.
6.3 How to perform a field calibration test
To perform a field calibration test, you must first Zero your Tetra unit 15 minutes or less before commencing the gas test instructions.
1. Follow steps 1 to 3 given in 6.2. Tetra will display an alternate screen
Click to
In 10 seconds
2. Press the button within 10 seconds to confirm Calibration.
If the button confirmation for calibration is not made within 10
seconds then the process will revert to gas test as in 6.2.
3. Apply calibration gas following step 4 in 6.2.
Tetra will display a progress bar at the bottom, the names of the gas
sensors fitted are shown in reverse image with a cross beside each.
Operate the Trigger regulator and apply gas to the Tetra whilst the
progress bar is counting down.
As gas flows the Tetra allows the sensors to respond and then adjust
the value for each gas channel to match the stored calibration gas
value within each sensor i-module. Provided all channels calibrate
successfully within the allowed time the calibration will be designated
successful. If any channel does not calibrate successfully it will remain
marked with a cross and screen a message ‘Gas test failed’ and ‘Send
for calibration’ will be displayed. A tick will appear against each
channel as the unit passes the test
4. To abort the Calibration test press the button at any time whilst the
test is in progress.
Gas test/calibration troubleshooting
6.4 Cal/Test
This can arise if having selected and confirmed calibration one or more (but not
all) of the sensors are not calibrate enabled. In this case calibrate enabled channels will calibrate, and non-enabled channels will Gas Test (bump) only.
Oxygen i-modules are usually not set to calibrate enabled as the calibration at
20.9% on atmospheric air during the zero process is more accurate and repeatable than using certified gas mixtures. Provided it completes a successful test
and the other i-modules fitted successfully calibrate the calibration due date for
oxygen will be reset during a Cal/Test.
6.5 Gas test/calibration troubleshooting
Possible Cause
No response to gas
Gas cylinder empty
Check gauge, replace cylinder
as needed
Hose blocked or kinked
Ensure no restriction to flow
Gas cylinder empty
Check gauge, replace cylinder
as needed
Gas cylinder out of date
Check date and replace as
Hose blocked or kinked
Ensure no restriction to flow
Calibration drifted
Calibrate Tetra
Gas flow not started immediately
Repeat test, starting gas
Gas cylinder empty
Check gauge replace bottle as
Gas cylinder out of date
Check date and replace as
Hose blocked or kinked
Ensure no restriction to flow
Calibration drifted
Calibrate Tetra
Stabilisation time too short
Reset using PC software
Menu Zero not performed
Tetra not field calibration
Select Zero from menu
Send for re-configuration
Tetra fails gas test
Tetra fails calibration
Tetra passes gas test
but will not enter
calibration mode
Note: Remove regulator from gas cylinder when not in use over a prolonged
For parts list, see section XI.
Maintenance and Calibration
VII. Maintenance and Calibration
Tetra is designed to operate almost maintenance free under most conditions.
However, some small items of routine maintenance are recommended.
To keep the display panel and operator button free from dirt build up, regularly
wipe over your Tetra unit with a damp cloth.
Inspect the front filter at regular intervals for dirt or damage. Replace with a
new filter/front grille if necessary, part number CO1852.
Zero and calibration
Tetra is supplied with an auto zero function on start-up. This function can
be configured to operate automatically, on user confirmation (see quick start
guide), or can be disabled. This configuration can be set with the Crowcon
Portables PC software, see section VIII. Tetra also has a zero function in the
menu. See section II.4.
Crowcon recommends, as a minimum, a monthly gas test to confirm sensor
operation. A test gas of known composition, needs to be applied, to verify sensor response and alarm function.
Instrument calibration of all sensors should be performed at 6 month regular
Calibration method
Tetra calibration can either be performed using the Portables PC software or
by use of the Gas Test Accessory Kit. Using the Portables PC software allows
calibration using either single gas mixtures, and calibrating each sensor in turn,
or using a multigas mixture for simultaneous calibration. The Gas Test Accessory
Kit allows calibration on a quad gas mixture for the standard 4 gas combinations of flammable, oxygen, carbon monoxide and hydrogen sulphide.
Calibration and Gas Testing require the use of the correct type of flow plate as
Non pumped units - use either the standard flow plate or the clip on
calibration flow plate C011005
Pumped units with software version 1V07 or lower. The pump is
Maintenance and Calibration
always running even in Calibration or Gas Test modes - it is essential
to use the C01874 'bellows' style flow plate.
Pumped units with software version 1V08 or later where the default
configuration is that the pump is automatically switched off in
Calibration or Gas Test mode. Use the clip on calibration flow plate
C011005 unless the default configuration has been changed to maintain the pump running for Calibration or Gas Test in which case it is
essential to use the C01874 'bellows' style flow plate.
Ozone detector calibrations
Always calibrate Crowcon ozone detectors with ozone only.
For ozone calibrations all fittings and pipework should be stainless steel, brass,
aluminium or PTFE. Fittings or pipework in other plastic materials such as Tygon
must not be used.
Gas flow rate:
It is important that the flow rate is set correctly as otherwise pressure effects
may distort calibration values and prevent the gas detector from working correctly. To calibrate Crowcon portable detectors the flow rate should be set
between 0.8-1.0 litres / minute (0.03-0.04 cubic feet / minute).
Normal safety precautions for handling ozone should always be observed along
with any special instructions that accompany the calibration gas cylinder or
generator being used.
Model specific instructions:
Below is information about the calibration of specific Crowcon detectors. This
differs between models due to the different interactions of sensors and gas
flows in each type.
For calibrating the ozone, the flow plate with four inlets (part number S012976)
should be used. The ozone sensor should always be at position 3 as marked on
the aspirator plate. Note that the standard flow plate must be used for calibrating the other gas sensors.
PC interface and software
VIII. PC interface and software
Tetra can be connected to a PC using an infrared optical link. The Tetra unit
has an optical communication port: an IR window is located on the top of the
unit. The PC requires a Crowcon infrared PC interface, part number MIS26003
and Crowcon Portables PC software. The adaptor connects to an RS232 port, a
USB-RS232 adaptor is also available from Crowcon.
The software provides the user with access to reconfigure alarm levels, operation, run calibrations, print reports and to access the event log.
1. Install Portables PC software on PC and install infrared adaptor.
The infrared communications are not IrDA. DO NOT install IrDA drivers,
if supplied with with the IR link kit.
2. Switch on the Tetra unit and move to within range of the adaptor.
3. Open the Portables PC software and either use the Wizard or the
Engineer’s Form, select Tetra and upload the configuration.
For more information on using the Crowcon Portables PC software, see
installed help file.
i-module replacement
IX. i-module replacement
1. Ensure you are in a non-hazardous (safe) area.
Switch off the unit
2. Remove any accessories, such as the flow adaptor, if fitted.
3. Remove the front cover grille by unscrewing the M3, 2 mm Allen screw
as shown the in the drawing, point 
Unscrew the side retaining M4, 3 mm Allen screws as shown in .
Remove the three sensor plate retaining screws as shown by point .
Ease the top away from the body, point .
Press down lightly on the rubber seal protecting the sensor housing
and slide forward, to clear the internal chassis from the sensor plate
aperture. With care, withdraw the whole instrument assembly.
Removing an installed i-module
1. Locate the i-module connection ribbon, squeeze the two retaining
lugs, on the module board, toward each other and pull out slightly,
this will release the ribbon.
2. Remove the retaining ring from the clips. Unclip the i-module from the
i-module replacement
two quick release fixings, push the sensor mounting out of the sensor
plate housing, taking care to retain any seals.
Installing or replacing an i-module
If replacing an i-module with one of the same type, instrument specific
configuration will be retained. If replacing with a different i-module its default
configuration will be loaded.
1. Unwrap the i-module from any packaging, ensure the sensor is fully
seated on the module board.
If you are installing a new i-module into a currently unused slot, you
will first need to remove the dummy i-module. Follow the i-module
removal instructions to do so.
2. Ensure the gasket is in place on the sensor, push the sensor through
the sensor aperture in the sensor plate housing. Click the quick release
fixings around the i-module board, ensuring the i-module is held in
place firmly and the sensor is still tightly located on the module board.
Replace the retaining ring on the clips.
3. Attach the ribbon connector by squeezing the two retaining lugs , on the
module board, toward each other and pulling out slightly. Slide the ribbon,
with the metal connectors facing away from the board, into the slot. Push
the retaining lugs back toward the sensor, this will grip the ribbon firmly.
Do not twist the connection ribbons.
Do not pull the sensor housing assembly too far from the PCB board.
Doing so may damage the cabling or electrical connections.
Re-assembling the Tetra unit
1. Ensure the connection ribbons and cables are tucked in. Slide the
whole assembly back into the casing. Ensure all gaskets are in place.
Replace the top and front cover grille.
2. Switch on your Tetra unit. The new sensor will be automatically
Check the filters and gaskets are all in good condition.
Replace if any items are faulty.
Refer to the troubleshooting guide if necessary.
X. Specification
122 x 128 x 57 mm (43/4 x 5 x 21/2 inches)
498 g rechargeable unit, including belt clip and
4 sensors.
Housing, degree of protection
Ingress protection IP65 (NEMA 4)
Operating temperature -20°C to +55°C (-4°F to +131°F)
Humidity 0-99% RH, non-condensing for continuous
Display 128 x 64 pixel
Warm up time 45 seconds approximately
Response time (typical) (T90) : approx 20 seconds for most toxic sensors, 10 seconds for oxygen.
±2% FSD, 6 months
Explosion protection Intrinsically Safe
ATEX Essential Health and Safety Requirement, clause
Safety certificate no.
Approval codes
ATEX II 2G EEx ia d IIC T4, (Tamb –20°C to +55°C)
Class I Division 1, Groups A, B, C and D.
Class I Division 1, Groups A, B, C and D T4.
Marine Equipment Directive
EN50014, EN50020, EN50018, 94/9/EC
CSA22.2, 152
EN50270, EN50271, IEC61508
Tetra can be supplied Wheelmarked compliant
with the Marine Equipment Directive. Contact Crowcon to obtain a copy of the MED certificate
Accessories and spare parts
XI. Accessories and spare parts
Accessory list
Crowcon part number
Aspirator Plate and Gasket
Aspirator assembly for pumped units
Aspirator assembly, non pumped units
Tetra Gas Test Accessory Kit for pumped units
Tetra Gas Test Accessory Kit for non-pumped units.
Refer to Section VII for applicability
Tetra Gas Test Accessory Kit. Refer to Section VII for applicability
Calibration Flow Plate for pumped units.
Refer to Section VII for applicability
Calibration Flow Plate for non-pumped units.
Refer to Section VII for applicability
Calibration Flow Plate. Refer to Section VII for applicability.
Quad Gas mixture for Gas Test Accessory Kit, 34 litre bottle 50%LEL
methane, 100ppm carbon monoxide, 15ppm hydrogen sulphide,
18% oxygen balance nitrogen.
Calibration gas contact Crowcon
- required gases depend on sensor combination
Battery charger power supplies
External PSU for Tetra Charger, UK 230 V 50 Hz
External PSU for Tetra Charger, US 110 V 60 Hz
External PSU for Tetra Charger, Euro 230 V 50Hz
230 V in line charger, no plug fitted.
110 V in line charger, no plug fitted.
*There are alternative flammable sensors for different applications. Contact Crowcon with the
instrument Serial No. to check correct sensor type.
i-modules cont:
0-25% oxygen O2
0-100 ppm hydrogen sulphide H2S
Accessories and spare parts
S011427 S011428
0-500 ppm carbon monoxide CO
0-20 ppm sulphur dioxide SO2
0-10 ppm nitrogen dioxide NO2
0-20 ppm nitrogen dioxide NO2
0-20 ppm chlorine Cl2
0-1000 ppm hydrogen H2
0-25 ppm hydrogen cyanide HCN
0-5 ppm phosphine PH3
0-1 ppm ozone O3
0-10 ppm hydrogen fluoride HF
0-1 ppm fluorine
0-100 ppm ammonia NH3
0-1000 ppm ammonia
Sampling accessories:
Aspirator assembly for non pumped units
Telescopic aspirator probe
3 foot Sample probe
Aspirator hose (please specify length in feet)
6 m Drop line
Water trap
Carrying and wearing:
Universal harness plate
Shoulder strap
Chest harness strap kit
Carry case, rechargeable units
Carry case, non-rechargeable units
Infrared adaptor for PC, plugs into RS232 port
USB to RS232 adaptor
Portables PC Software CD
Spares / consumables:
Alkaline battery, AA (3 required)
Rechargeable Li-ion battery pack assembly
Aspirator bulb
Sensor filter assembly
Dummy sensor module
M04787 Rubber sealing bung for charger socket
i-module O-ring seal
Sensor clip retaining ring
For calibration gases consult Crowcon
Troubleshooting guide
XII. Troubleshooting guide
error message
Instrument won't switch on Flat battery. Pump not running
The pump is a PC
configurable option.
No confidence beep
Function disabled.
Gas reading when no gas
Zero drifted.
Unstable/inaccurate gas Sensor failure
Autozero failed
Zeroing in contaminated atmosphere
Cannot autozero due to Zeroing in alarm
contaminated atmosphere
Calibration expired
The calibration due date has passed
Flow fail clear blockage Sample tube is blocked with water or dirt or kinked
LCD too faint/dark
Contrast setting
Recharge or replace battery.
Reconfigure with PC software.
Reconfigure with PC software.
Restart instrument in clean air.
Do not use; exit hazardous area immediately. Return instrument for recalibration or sensor replacement.
Switch off and restart in
clean air.
Switch off and restart in
clean air
Send for calibration
Clear blockage and press
button to restart pump
Adjust using Portables
PC software.
Fatal/Auto shut
User alert
Appendix: Limitations of sensors
Appendix: Limitations of sensors
Sensor limitations
The sensors used in Tetra have limitations common to all such gas sensors,
and users should be aware of the points listed below. Crowcon can advise on
particular situations and suggest alternative sensors if the instrument is likely to
experience extreme conditions.
Tetra uses a catalytic flammable gas sensor, which measures the flammability of
the gas. For this reason, readings displayed on the unit will be unreliable over
concentrations of approximately 120% LEL. Oxygen is necessary for catalytic
sensors to operate. A 'pellistor saver' is used to disconnect power to the pellistor sensor in the event of over-range to prevent burn out. This locks out for
200 seconds after which a button press will reconnect power to the pellistor. If
the sensor power is reconnected when the unit is exposed to an over-range gas
concentration there is a risk of damage to the pellistor sensor. Restart should
be carried out in a known fresh air environment. Depleted oxygen levels can
reduce the flammable gas reading, and if oxygen levels are below safe breathing limits it should be assumed that the flammable reading is low.
Electrochemical gas sensors contain chemicals. Extreme levels of humidity can
also cause problems. The sensors are rated for an (average) ambient of 15-90%
R.H. However they are used from the tropics to deserts to tundra without this
normally being a problem.
Water should not be allowed to collect on the sensors as this may impede gas
Persistent exposure to high levels of toxic gas will shorten the life of toxic sensors. If the high level gas is corrosive (e.g. hydrogen sulphide) damage may
occur over time to metal components.
Sensors may be cross sensitive to other gases. If unsure, contact Crowcon or
your local agent.
Tel: +44 (0)191 490 1547
Fax: +44 (0)191 477 5371
Email: northernsales@thorneandderrick.co.uk
Website: www.heattracing.co.uk
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