BRUEL & KJAER 1306 User manual
InstructionManual
Vol.1
Toxic-gas Monitor Type 1306
Operation and Interface
The Toxic-gas
Monitor
Type 1306 is
an
E!X-
tremely reliable and highly selective
monitor
of
a gas, or group
of
gases. Gas-selectivity is
determined by the optical filter installed. The
1306 operates
automatically-
drawing
in
a
sample
of
air from its environment,
at
user-
selectable intervals, and measuring the
con-
centration
of
the monitored gas in it. ·
The 1306 is linked
to
a
computer
so that the
user can request measurement/test data from
it, and remotely control
it
by sending
it
com-
mands and control data.
+
BrUel
&
Kjcer
Brilel
&
Kjcer
~
DK-2850 Nrerum ·Denmark· Telephone:
+452800500
·Telex: 37316 bruka dk ·
Fax.:
02801405
Prinled
1n
Denmark:
K.
Larsen & S0n
A/S
·
DK·2600
Glostrup
1306
Vol.1
English
OK
BE0981-11
InstructionManual
Vol.1
Toxic-gas Monitor Type 1306
Operation and Interface
The Toxic-gas
Monitor
Type 1306 is
an
ex-
tremely reliable and highly selective monitor
of
a gas, or group
of
gases. Gas-selectivity is
determined by the optical filter installed. The
1306 operates
automatically-drawing
in a
sample of air from its environment, at user-
selectable intervals, and measuring the con-
centration of the monitored gas in it.
The 1306 is linked
to
a computer so that the
user can request measurement/test data from
it, and remotely control it by sending it
com-
mands and control data.
+
Bri.iel
&
Kjaer
TOXIC-GAS
MONITOR
TYPE 1306
From serial no. 1336777
June 1988
CONTENTS
1.
INTRODUCTION AND SPECIFICATIONS {PRODUCT
DATA)
.............................................................................. 1
2.
OPERATION .................................................................................................................................................................5
2.1. INTRODUCTION.................................................................................................................... 5
2.2. INSTALLATION OF THE MONITOR................................................................................... 6
2.3. THE MEASUREMENT PRINCIPLE .................................................................................... 6
Determination
of
Water-vapour
's Signal
Contribution
................................................. 7
2.4. THE GAS-MEASUREMENT SEQUENCE......................................................................... 7
Time
Taken
to
Complete
a Gas Measurement.............................................................. 8
2.5. OPERATING MODES........................................................................................................... 9
2.6. START
-UP
SEQUENCE OF THE 1306 ............................................................................. 9
2.7.
SELF-
TESTS......................................................................................................................... 9
Almost
Continuous Self-tests............
..
...........,
..
..............................................................
11
Regular Self-tests.............................................................................................................. 13
The Gas-measurement Sequence
Self-tests
................................................................ 16
2.8. CONDITIONS CAUSING THE 1306
TO
RESET............................................................. 17
2.9. COMMUNICATING WITH THE 1306................................................................................ 18
Sending Data
to
the 1306................................................................................................. 18
Requests
for
Data
from
the 1306 ...................................................................................
20
Sending
Commands
to
the 1306.......................
...
...........................................................
21
2.1
0.
THE STATUS REPORT ...................................................................................................... 23
Warning Flags..................................................................................................................... 23
Operating-error
Flags ....................................................................................................... 26
3.
INTERFACE AND COMMUNICATIONS PROTOCOL..........................................................................................
29
3.1.
RS
485 INTERFACE ............................................................................................................ 29
Introduction
......................................................................................................................... 29
Differential Transmission..................................................................................................
29
Use
of
Equipment with an
RS
232 C Interface.............................................................. 30
Large Systems................................................................................................................
....
32
3.2. DDCMP PROTOCOL...................
..
..................................................................................... 34
Introduction
......................................................................................................................... 34
Cyclic
Redundancy
Checking
(CRC).............................................................................. 35
Data
Format
......................................
..
..
.............................................................................. 35
Message Headers.............................................................................................................. 35
Exchange
of
Messages..................................................................................................... 38
Response
of
the
Computer
to
Errors
............................................................................ 39
Response
of
the 1306
to
Errors
......................................................................................
41
Initializing the System....................................................................................................... 42
Block
Data Transfers ........................................................................................................ 43
4.
DATA
TRANSFER BETWEEN THE 1306 AND THE COMPUTER ..................................................................... 44
4.1. INITIATING A
DATA
TRANSFER ...................................................................................... 44
4.2.
DATA
FORMATS ................................................................................................................. 45
4.3. CONTROL
DATA
.................................................................................................................47
4.4. MEASUREMENT AND TEST
DATA
................................................................................. 48
Primary
Data
Block
...........................................................................................................48
Total Data
Block
................................................................................................................. 50
Measurement Test Data Block ........................................................................................ 52
Software Test Data
Block
................................................................................................. 62
Access
External
Ports
....................................................................................................... 63
4.5. COMMANDS
TO
THE 1306.............................................................................................. 64
Forced
Commands
............................................................................................................64
Test
Commands
.................................................................................................................66
Order
of
Priority
of
Commands
...................................................................................... 68
Transfer
of
Commands
.....................................................................................................68
4.6. EEPROM
DATA
...................................................................................................................69
Optical
Filter
Factors
........................................................................................................ 69
Optical
Filter
Identity
.........................................................................................................
71
Calibration
Factors
............................................................................................................73
Calculating the CRC
Check
Sum.................................................................................... 75
4.7. ERROR STATUS FLAGS....................................................................................................
76
5.
CALCULATION
OF
CALIBRATION FACTORS ......................................................................................................
79
5.1. INTRODUCTION..................................................................................................................79
5.2. ANALYSIS OF THE SIGNAL MEASURED
IN
THE ANALYSIS CELL ........................ 79
5.3. CALCULATION OF THE GAS CONCENTRATION ........................................................ 80
5.4. CALCULATION OF THE NEW CALIBRATION FACTORS ............................................
82
Calculation
of
the New
Concentration
Offset
Factor
(Cottset)
....................................
82
Calculation
of
the New
Humidity
Gain
Factor
(91)
•••••••••••••••••••••••••••••••••••••••••••••••••••••••
83
Calculation
of
the New
Conversion
Factor
(fc)............................................................ 84
5.5. COMPARISON
OF
THE
"OLD"
AND
"NEW"
CALIBRATION FACTORS ................... 85
5.6. TRANSFER OF THE NEW CALIBRATION FACTORS
TO
THE 1306's EEPROM..... 86
6.
SERVICE AND REPAIR............................................................................................................................................
87
·
USES:
• Unattended monitoring of toxic gases and
vapours
• Detection of accidental releases
• Monitoring of process emissions
• Occupational health and safety measurements
FEATURES:
• Highly selective and sensitive
• Linear over a wide dynamic range
• Unattended operation -typically 3 months
• Accurate concentration measurements
• Extremely reliable due to self-testing procedures
• Compensates for water-vapour
and
temperature
fluctuations
• Remotely controlled
by
computer
• User-friendly software available
• Very
stable-
infrequent calibration required
• Easily
maintained-
running-costs are low
• Protected against voltage surges
Introduction
The
Brtiel & Kjrer Toxic-gas Moni-
tor Type 1306 is a highly sensitive,
stable
and
reliable
instrument
de-
signed to automatically monitor toxic
gases
and
vapours in
harsh
environ-
ments.
Its
measurement technique is
based on photo-acoustic infra-red
spectroscopy.
The
1306 can
thus
be
used to monitor almost any gas which
abso:..·bs
infra-red light. By choosing
an
appropriate optical filter from
the
wide range of narrow-band filters
available,
the
1306 can selectively
measure
the
gas ofinterest.
The
1306's
detection threshold is gas-dependent
but
typically in
the
parts
per billion
(109) to
parts
per million region.
Its
wide dynamic range allows
it
to mea-
sure concentrations four orders of
magnitude (i.e. a factor of 104) higher
than
its detection threshold.
BP 0788-11
The
Toxic-gas Monitor's running-
costs are low as
it
is
able to function
efficiently even under extreme envi-
ronmental conditions for long periods
of time without maintenance,
and
with minimal supervision.
The
weather-proofed case of
the
1306 encloses both
the
system for
measuring gas concentration,
and
the
electronics for processing signals.
For long-term monitoring
the
1306
and
its Power Supply
ZG
0309 are
mounted on a
mast
in a suitable loca-
tion,
and
the
1306 is linked to a com-
puter.
This
computer acts as a control
station. Using
the
Applications Dis-
kette BZ5003 provided, users can
communicate with a single 1306, con-
trolling
it
remotely, collecting mea-
surement
and
self-test
data
from
it
and
calibrating
it
in situ.
type 1306
Toxic-gas Monitor
Brtiel& Kjrer Application Software
Type 7619 is available for controlling
up
to
31
Toxic-gas Monitors in a mon-
itoring network.
This
user-friendly
software automatically collects, analy-
ses and presents measurement and
self-test
data
from all the monitors in
a network,
and
enables in situ calibra-
tion of each 1306 in
the
network.
The
measurement
and
self-testing
sequences of
the
1306 are completely
automatic.
The
1306's comprehensive
self-testing procedures enable
it
to de-
tect
and identify any relevant system
fault and report
it
to
the
control sta-
tion. Measurements stop
if
the
1306
is
unable to measure reliably because of
a system fault,
but
as soon as
the
fault
has been corrected,
the
1306 automat-
ically resumes measurements.
Optical Window )
(Air
Shunt
Infra-Red
Source
Optical Filter
UAXXXX
Humidity
Lamp
Inlet
·Valve (1)
Fine Air-Filter
Coarse
Air-Filter
87041111
Fig. 1.
The
measurement
system
of
the Toxic-gas Monitor
Correct positioning of
the
1306 is
vital.
The
circulation
of
air
around
the
1306
must
be sufficient
to
ensure
that
the
air
around
it
is representative of
the
air
in
the
area
being monitored.
Method
of
Operation
At
user-selectable intervals, a
pump
draws a sample
of
air from
the
moni-
tor's environment, into
the
analysis
cell, through two air-filters.
The
cell is
then
sealed by closing its inlet
and
outlet
valves (see Fig. 1). Light from
an
infra-red source is reflected from a
mirror
and
passed first through a
chopper, which pulsates it;
then
through
an
optical filter, which
trans-
mits light of defined wavelength into
the
analysis cell
through
a window.
The light transmitted by the optical fil-
ter is selectively absorbed by the gas
being monitored, so if any of the moni-
tored gas is present in the cell
it
will
absorb this light, causing the tempera-
ture of the gas to increase.
As
the cell is
sealed, this temperature increase causes
an
equivalent increase in the pressure
ofthe gas. Because the light is pulsating
at
the chopper frequency, the pressure
will also fluctuate
at
this frequency,
creating
an
acoustic
wave
in the cell
which is directly proportional to the
concentration of the gas in the cell.
This is the photoacoustic effect.
Two sensitive microphones mount-
ed within
the
cell wall measure
the
acoustic signal which is
then
processed
by
the
1306. Measurement results are
sent
to
the
control
station
on request.
2
A complete
measurement
takes 45-
55
s - this includes
the
time
taken
to
purge
the
cell.
The
time between mea-
surements is defined by
the
user.
Selectivity
The
selectivity of
the
Toxic-gas
Monitor is determined by
the
installed
optical filter. A wide range of narrow-
band
optical filters is available from
Brtiel& Kjrer.
By
studying
the
absorp-
tion
spectrum
of
the
gas
to
be moni-
tored as well as
the
absorption spec-
trum
of any other gas which is likely
to
be found
in
the
ambient air
in
the
same area,
the
most
appropriate
opti-
cal filter
can
be chosen. Refer
to
the
Product
Data
Sheet
for
the
Optical
Filters for details.
Water vapour, which is nearly always
present in the air samples drawn into
the 1306 for analysis, absorbs infra-red
light slightly
at
nearly all frequencies
and therefore contributes to the signal
measured in the cell. However, by us-
ing a humidity lamp, water-vapour's
contribution is measured separately
during each gas measurement se-
quence, so
that
the 1306 can compen-
sate for water-vapour's interference.
Setting-up the 1306
The
user sets-up
the
monitor by
sending
it
control
data
which specifies
the
following:
• the time between the finish
of
one
mea-
surement and the start
of
the next (this
determines the measurement frequency);
•
the
alarm
level-
t4at
is,
the
con-
centration of monitored gas which,
if
measured, causes
the
1306
to
perform
measurements continually,
and
trig-
gers any external alarm which may be
connected to
the
network.
Modes
of
Operation
The
1306
has
four different modes
of operation.
Three
of
these modes are
dependent upon
the
concentration
of
monitored gas measured
in
the
analy-
sis cell (see Fig. 2).
(1)
Normal
Mode
The
1306 operates
in
this mode as
long
as
the
concentration of
the
moni-
tored gas
it
measures is below a level
called the intensification level.
The
in-
tensification level is
half
the
alarm
level (see Fig. 2). Gas measurements
occur with a frequency specified
in
the
1306's control data.
(2)
Intensification
Mode
The
1306 operates
in
this mode
as
soon as
it
measures a concentration
of
monitored gas which is
greater
than
the
intensification level. While operat-
ing in this mode
the
frequency of gas
measurements increases as
the
moni-
tored-gas concentration increases, un-
til
the
alarm level is reached.
(3)
Alarm
Mode
By
the
time
the
concentration
of
the
monitored gas reaches
the
alarm level
gas measurements are being
taken
continually.
(
4)
Power-
Down
Mode
The 1306 operates in this mode: (a) if
it
is
not able to measure gas concentra-
tions reliably, or
(b)
if commanded to
do
so
by the control station
(e.g.
during
maintenance). In this mode the 1306
stops performing gas measurements and
stops testing its measurement system.
Gas__.
Intensification Alarm Concen-
level
Level tration 87041411
Fig.
2. Graph showing how the 1306's operat-
ing mode
and
measurement "frequen-
cy" is dependent on the concentration
ofmonitored gas measured by the 1306
Remote Control
The
user controls
the
1306 remotely
by sending
commands/requests
via
the
control
station
.
Commands
The
user
can
command
the
1306 to
perform
any
one of a
number
of mea-
surements or tests, or to change its
mode of operation,
at
any
time.
The
1306 responds by immediately stop-
ping
what
it
is doing
and
carrying
out
the
command.
This
facility is particu-
larly useful in
alarm
situations
and
during service
and
maintenance
.
Requests
The
1306 stores the results of its
most recently completed measurement
and self-test sequences. This
data
is
continuously
updated
and
can be re-
quested from the 1306
at
any time with-
out disturbing its mode of operation.
Communication
A shielded, balanced, two-wire com-
munication cable is used to connect
the
1306
to
its control
station
(com-
puter).
The
cable handles communica-
tions
in
both
directions. A single com-
puter
can
control
up
to
31
Toxic-gas
Monitors,
and
the
total
distance be-
tween
the
computer
and
the
last
1306
on
the
cable can be
up
to 12
km
, de-
pending
on
the
number
of
1306s being
used. Modems
can
be used to increase
this
distance.
A special procedure (DDCMP)* is
used to check all
data
transmitted
on
the communication cables. This proce-
dure makes it possible to reduce the
data-transmission error-rate almost to
..
Power Supply Unit
177710ther
compatible equipment
l.LL..J (e.g. Wind Velocity
Monitor
.)
RS485
RS
232C
,--1
Control
I I Station
.I.
I
lO
Converter I
co
'<t
RS
485-
I
en
a:
RS
232C I
~
L_
~I
'<11
~I
Self-tests
Frequency
Switch settings; temperature
of
gas
in
analysis
cell;
voltage
supply
to
the 1306;
Lid
(to
see
if
1306 has been opened); A-D every 260
ms
converter
Software; processing system every 18 s
Humidity
lamp;
temperature
of
I.R. source; frequency
of
same
as
gas
chopper measurement frequency
Microphones; preamplifiers; valves; air pump; air-shunt every 30
min.
T01491GBO
Table 1. Self-tests made by the Toxic-gas Monitor
zero. Each 1306 is given its own address
and the DDCMP enables the control
station to communicate individually
with each monitor connected to it.
The
control
station
and
the
1306
communicate via
the
RS-485 inter-
face.
This
interface was chosen in
preference
to
the
RS-232C interface,
which most computers use, for
three
important
reasons:
(1)
it
allows faster
serial transmission of data;
(2)
it
al-
lows
up
to
31
monitors to be connect-
ed
in parallel on a single cable
to
a
single
computer
which controls
them,
so
that
if
any
monitor in
this
network
stops functioning or is disconnected,
the
control
station
does
not
lose con-
tact
with all
the
other
monitors in
the
network (see Fig. 3).
The
monitors in
this network
can
be 1306s or
any
other
monitors which use
the
same interface
and
protocol, for example wind veloci-
ty/direction
monitors;
and
(3)
the
RS-
485 interface
standard
allows a
much
greater distance between
the
comput-
er
and
the
last
1306 on
the
cable.
A
computer
fitted
with
an
RS
232C
interface
can
be used as a control sta-
tion
by using
an
interface converter in
the
monitoring network (see Fig. 3).
* Digital Data Communications
Me
ss
age
Pr
otocol
developed by Digital Equipment
Co
rporation.
Reliability
The Toxic-gas Monitor has been rigor-
ously tested to ensure reliability of per-
formance and results. Performance reli-
ability
is
ensured
by
the comprehensive
series of self-tests which the
1306
contin-
uously performs. See Table 1
for
details.
A
status
report,
which summarises
the results of the 1306's self-tests, is
sent to the control station with all mea-
surement results. The user can therefore
see
at
a glance what, if anything, has
affected the accuracy of the measure-
ment; or which fault has caused the
1306 to stop taking gas measurements,
so
that
appropriate action can easily be
taken to correct the fault.
As soon as
the
condition causing
the
fault is corrected
the
1306
automati-
cally
starts
up
again.
Power Supply
The Toxic-gas Monitor requires a
12
V
DC
power supply. This can be obtained
either: from the
AC
mains
by
means of
the Power Supply
ZG
0309
which
is
pro-
vided as an accessory; or from a
12
V car
battery. A car battery can also be used to
provide power for short-term monitoring
from a stationary vehicle.
Address 29
Type 1306
Power~:!
Supply
Cable
87115211
Fig.
3.
A simple monitoring network comprising Toxic-gas Monitors
and
other compatible equipment
3
The
1306
is
provided with an input
filter which protects it from transient
voltage surges on the power supply
caused,
for
example,
by
lightning strikes.
The
1306
resumes its automatic opera-
tion as soon as the voltage supplied to it
falls within operational limits.
Maintenance
Regular maintenance
of
the
1306 in-
volves calibration
and
change of
the
All terms relating
to
gas analysis are in
ac-
cordance with the
definitions
set
out
in the
ISO Draft International Standard 8158
Details about the
optical
filters which are
available
for
use with the 1306 can be found
in the "Optical Fil
ters"
Product Data Sheet.
An optical
filter
UA XXXX is installed in the
1306, which is then
zero-point
calibrated be-
fore delivery. Calibration with a
specific
gas
is optional. A "calibration
chart
" gives details
about the installed
optical
filter
and the
ca
li-
brat
ion
of
the 1306.
MEASUREMENT TECHNIQUE:
Photoacoustic
infra-
red
detection
RESPONSE TIME:
45s -55s (time taken
to
purge the cell, and
measure the gas concentration in the new air
sample).
ACCURACY:
Zero
Drift:
Typically = Detection Threshold per 3 months•
Influence
of
temperature
•:
insignificant-
compensated
for
internally.
Influence
of
pressure.&: ± 1,
5%
of
detection
threshold/mbar
A gas concentration equal
to
1%
of
the
maxi-
mum measurable concentration was used in
determining the following specifications
Repeatability:
1%
of
measured valuee
Range
Drift:
± 2,5%
of
measured value per 3
months•
Influence
of
temperature• : insignifi
cant-
compensated
for
internally.
Influence
of
pressure.&: - 0,01%
of
measured
value/mbar
MEASUREMENT
RANGE:•
Detection
Threshold:
is gas-dependent but
ranges
from
parts/million
(ppm)
to
parts/bil-
lion (see Table
for
examples
of
the
detection
threshold
of
some pure gases/vapours).
Dynamic
Range:
four
orders
of
magnitude
(that is, the upper detection
limit=
10000
times the
lower
detection limit)
GENERAL:
Cabinet:
complies with IEC
529
&
IP
53
Stan-
fine air-filter.
The
frequency with
which these two operations need
to
be
performed is dependent on
the
1306's
measurement frequency,
and
on
the
amount
of suspended
matter
(e.g.
dust) in
the
air
it
is monitoring.
The
status
report
informs
the
user of when
the
1306's fine air-filter
needs to be changed.
It
is often practi-
cal to calibrate
the
1306 when its fine
air-filter is changed (typically 4 times
a year). Calibration in
the
field
(in
Specifications 1306
Gas/Vapour Detection Threshold
(ppm)
Phosgene 0,03
Vinyl chloride 0,2
Ammonia 0,3
Styrene 0,2
Perchloroethylene 0,
05
Ethylene oxide 0,1
Benzene 0,8
Total hydrocarbons
0,1
(with
ref
.
to
propane)
T0
1
814GBO
dards. Resistant
to
rain falling at a maximum
angle of
60
°
to
the vertical axis. Dust resistant
Dimensions:
Height: 400 mm (15,7 in)
Width: 200 mm (7,9 in)
Depth: 102 mm (4,0 in)
Weight:
5,5 kg
(12,1
lbs)
Operating
Temperature:
-20°C
to
+50
°C
Relative
Humidity:
95%-100% relative hu-
midity
at
soo
C
Power
Requirement:
Power Supply ZG 0309 complies with IEC348
Class 1 Standards. It converts: 90, 100,110,
120,130,200,210,220, 230, 240 VAC ± 10%,
50/60Hz
to
12 V DC. Power consumption:
-SOVA
. Alternatively, a DC
power
supply
(e.g. a car battery) providing 12 V
(+15%/
-20%)
to
the input terminals
of
the 1306 can
be used. The 1306 is supplied with an
at
-
tached 4m power cable.
Power
Consumption:
During measurements:
34
W peak (start)
and
18
W
operating.
On
standby: 2W (power-down
mode)
Vibration
Sensitivity:
Strong
vibrations
occuring
at
a frequency
of
20 Hz can
compro-
mise the detection-threshold
specificat
ion.
Acoustic
Sensitivity:
Not
influenced by
ex-
ternal sound
situ)
is performed using a known con-
centration
of
either
the
gas to be mon-
itored, or a
substitute
gas.
If
the
1306
stops taking gas measure-
ments the user can request detailed re-
sults of all the 1306's self-tests. Using
this data, service engineers can quickly
diagnose any fault and perform neces-
sary repairs without
delay.
This means
that
service costs can be minimised and
that
the
1306
is
out of operation for the
shortest possible time.
Electromagnetic
Compatibility:
Comp
lies
with U.S. FCC requirements
for
class B
computing devices.
Electromagnetic
Pulse (EMP)
Protection:
In
accordance with CCITT recommendation
K17.
COMMUNICATION:
The 1306's digital interface complies with
the
EIA Recommended Standard
RS
485. The
Digital Data Communication Message
Proto-
col (DDCMP) is used
to
ensure
error-free
and
synchronized data transfer. The 1306 is sup-
plied with an attached 4m communication
ca-
ble. The Application Diskette BZ5003
provid-
ed allows users to control a single 1306. B& K
Application
Software Type 7619 is available
which allows users
to
control
up
to
31
Toxic-
gas
Monitors
in a network.
ACCESSORIES INCLUDED:
Application Diskettes .
....
..
.
..
...
..
............ BZ 5003
Power Supply ........
...
..
..
....
.......
..
.....
...
.
....
ZG 0309
Spare Fine
Air-f
ilter Thumbscrew
Unit,"
0"
-r
ing & Retaining Disc
...
..
..
.
..
.UA 0994
Fine
Air-filters
(10) .
..
..
..
.......
....
.....
...
.
..
.
..
OS
0714
Coarse
Air-filter
Unit (2) .
...
..
.............
..
.UC 0193
Calibration Kit consisting
of
:
Teflon Tubing (4m)..................
......
.......
..
.
AT
2177
Calibration Stub.
..
.........
..
...
...
....
..
.........
..
DB
3023
"Y"-piece
.....
....
...........
...
....
..
.·.................
..
UD
5001
"0"-ring
(4) .
..
........
..
.....
..
...
...
....
..
........
.
....
.
YJ
0770
Threaded Nut...
..
.
....
....
..
..
...
..
...............
...
.
YM
0652
Spare Fuses:
2 x 125
mA
.
...
..
..
............
...
..
...
.........
....
.
...
..
VF
0030
2 X 2,0 A.............................
..
....
.....
....
...
..
..
VF
0010
2 X 4,0 A.........
...
..............
......
..
.......
...
.
....
..
VF
0045
Allen Key
to
open/close
the 1306....
..
QA
0161
Special Key
to
install
optical
fil
ter
...
..
QA
01
62
"
C"
spanner (wrench) ...................
..
......
QA
01
81
Tweezers .....................
..
...............
..
....
..
...
QA
0164
ACCESSORIES AVAILABLE:
Optical Filters (22)...........
..
....
.UA0968-UA0988
....
.....
....
...
..
....
.
..
....
............
..
..
..
..
...
..
..
..and UA0936
RS
232C-RS 485 Converter................WQ 0677
Communication Cable with
2 x 25pin connectors......
....
....
...........
...
WL 0814
Communication Cable with a 25-
pin and a 9-pin connector.
....
..
.
..
....
..
.. WL 0815
REFERENCE CONDITIONS:
• Measured
at
20
°C, 1013 mbar, and relative
humidity (RH): 60%.
• Measured
at
1013 mbar, and
RH
: 60%.
.&
Measured
at
20°C
and
RH
: 60%.
For information on the installation
of
the Toxic-gas
Monitor
contact
your local Bruel & Kja3r representative.
2.
OPERATION
2.1. INTRODUCTION
The Toxic-gas
Monitor
is
primarily
designed
for
long-term monitoring
of
toxic gases in
permanent monitoring networks. Monitoring networks can vary in size and
complexity
depending on the user's requirements. The most simple network comprises a single
Toxic-gas Monitor and its power supply, mounted on a mast in a suitable location, and
linked to a computer -see Fig. 2.1.
Communication cable
AS 485
Fig. 2.
1.
A
simple
monitoring
system
To
AC
mains
power supply 880395
A
computer
program (software) is required to enable the user to communicate with the
1306 via the computer keyboard. Software is supplied with the Toxic-gas
Monitor
in the
form
of
an Applications Diskette BZ5003. This software allows the user to communicate
with a single 1306 via an
AT
or
PS2
IBM computer. It allows the user to request some
measurement results from the 1306; send new control data to the 1306, and calibrate the
1306. The use
of
this software is described in detail in Volume 2
of
the Instruction
Manual
for
the 1306.
Full communication with one
or
more 1306s requires more sophisticated software than
that provided. Optional software which is especially designed
for
this purpose is the
BrOel
& Kjrer Type 7619 "Software
for
Toxic-gas Monitoring". This software allows the
user to communicate fully, via the computer keyboard, with every 1306 in a monitoring
network. The keyboard commands used to communicate with the 1306 are software-
dependent and therefore will not be discussed here, but in the Instruction Manual
for
the
software.
In
this chapter we will only discuss those aspects
of
the operation
of
the 1306
which are independent
of
the software used.
5
Users who wish to write their own software are provided with all relevant information to
enable them to do so in Chapters
3,
4 and 5
of
this manual, and some information is
also provided on the diskette mentioned previously.
2.2. INSTALLATION
OF
THE MONITOR
A full description
of
all the details involved in the installation
of
the 1306 can be found in
Volume 2
of
the Instruction Manual
for
the 1306.
2.3. THE MEASUREMENT PRINCIPLE
6
An overview
of
the Toxic-gas
Monitor's
measurement principle is given in Chapter 1
of
this manual. However, in order to fully understand the various measurements performed
by the 1306 during a gas-measurement sequence, a more detailed description
of
the
effect
of
infra-red light on the air sample in the analysis cell is necessary.
When broad-band infra-red light, that is light with a wide range
of
frequencies, is passed
through a particular gas, the gas will selectively absorb light at particular
frequencies-
absorbing some frequencies
of
light more strongly than others. Every gas has its own
unique absorption spectrum. Fig. 2 in Chapter 1 illustrates a typical absorption spectrum
of
a gas. By carefully choosing an optical filter which only transmits light in a region
of
the spectrum where the gas to be monitored absorbs strongly, the 1306 can selectively
measure the concentration
of
this gas.
4,0
5,0
6,7
1~
wavelength (!lm)
Q)
(.)
c
~
~
Q)
.E
0"
(/)
(/)
0
c
~
~
o·
~
:I
4000 3500 3000 2500 2000 1500 1000
cm
-1
wavenumber 880334
Fig. 2.2. High resolution
transmittance
spectrum
of
water
vapour
Gases normally found in atmospheric
air
do
not absorb -to any measurable extent -
the light which is transmitted by the optical filter, and therefore they are not considered
to "interfere" with the signal which is measured in the analysis cell. However, water
vapour, which is almost always present in the
air
sample in the cell, absorbs infra-red
light at nearly all frequencies over a large region
of
the spectrum (see Fig. 2.2). Thus, no
matter which optical filter is installed in the 1306, some
of
the infra-red light reaching
the cell will be absorbed by the water vapour present and produce a signal which con-
tributes
to
the total signal measured in the cell when the infra-red light is on. Because
the signal produced by water vapour "interferes" with the signal produced by the gas
being monitored, it has to be measured separately so that the 1306 can compensate
for
water-vapour's
contribution.
2.3.1. Determination of Water-vapour's Signal Contribution
A very small lamp (humidity lamp) is mounted between the optical filter and the analysis
cell
window
(see Fig. 1 in Chapter 1
of
this manual). When this light is switched on it
emits pulses
of
infra-red light with wavelengths between approximately
0,5J.Lm-
3
J.Lm.
This
light is filtered by the glass covering the lamp's filament, as well as the analysis-cell
window, so that the wavelength
of
the light entering the cell is between
2-3
J.Lm.
Water
vapour absorbs strongly in this region
of
the spectrum (see Fig. 2.2) and therefore
pro-
duces a signal which can be measured. The greater the concentration
of
water
vapour
in
the cell (that is, the higher the humidity
of
the air in the cell) the greater the signal
produced by it. This is why the measurement
of
this signal is often referred to as the
"humidity"
measurement.
There are not many toxic gases which strongly absorb infra-red light in the
2-3
J.Lm
region
of
the spectrum and therefore, if any such gas is present in the cell during a
humidity measurement, it will not interfere significantly with the signal produced by wa-
ter-vapour.
By measuring the total signal in the cell when the humidity lamp is on, water-vapour's
signal contribution to the total signal measured in the cell when the infra-red
light
is on
can be determined. Details
of
this procedure are provided in Chapter 5
of
this manual.
2.4. THE GAS-MEASUREMENT SEQUENCE
Inlet valve open;
Infra-red source on;
Chopper started
!
r·
.ta,.ed
Outlet valve open
During the gas-measurement sequence a series
of
operations and measurements are
performed which enable the 1306 to calculate the concentration
of
the monitored gas in
its analysis cell. The sequence
of
these operations and measurements is illustrated in
Fig. 2.3 and can be described as follows:
1.
The inlet and outlet valves are opened; the infra-red light source is switched on;
and the chopper and pump are started.
2.
When the analysis cell has been thoroughly flushed, the pump is stopped and
the valves are then closed so that the air sample is sealed in the analysis cell.
The air in the analysis cell is still turbulent at this stage, so the 1306 waits
3-
4s to allow the
air
in the cell to stabilise before starting the measurement
discussed in the next step.
Inlet valve closed;
Pump stopped
Stabilisation
of air in
analysis cell
1 Gas measurement
15 20
21
tt
Gain adjustment
Outlet valve
closed
Infra-red source off;
Chopper stopped
Gas measurement
finished
Humidity
lamp on
li
Humidity
36
37 38
measurement
ru
Gain
adjustment
Calculation
of
gas
concentration using
previous humidity
measurement
Fig. 2.3.
The
gas-measurement sequence
of
the 1306
Humidity
measurement
r·····
45
Calculation of gas
concentration using
"new" humidity
measurement
Time (s)
880437
7
3.
A quick preliminary measurement is made
of
the total signal in the analysis cell.
This measurement allows the gain
of
the
amplifier
to
be set to its
optimum
value.
4.
The total signal in the cell is measured. The infra-red light source is switched
off, and the chopper is stopped. The total signal is compensated
for
water-
vapour's signal contribution using the humidity value measured during the previ-
ous gas-measurement sequence, and the gas concentration calculated in
mg/m
3.
5.
The humidity lamp is switched on. A
quick
preliminary measurement is made
of
the total signal in the analysis cell. This measurement allows the gain
of
the
amplifier to be set to its optimum value.
6.
The total signal in the cell is measured. The humidity lamp is switched off.
7.
The total signal measured in
(4)
above is now compensated
for
water
vapour's
signal contribution just determined (in step
6),
and the gas concentration is
calculated in
mg/m
3.
The whole gas-measurement sequence takes between
45
s-
55
s to complete. However,
users can get the results
of
a gas measurement
37-
40
s after the
start
of
a measure-
ment, but this gas concentration is that which is calculated using the previous humidity
measurement (see step 4 above). Under normal circumstances the humidity in the cell
will not fluctuate widely between one gas measurement and the next, and therefore the
results obtained in step 4 and step 7 will not
differ
greatly.
2.4.1. Time Taken to Complete a Gas Measurement
8
The whole gas-measurement sequence can be performed in
45
s.
However, up
to
10s
extra time is sometimes needed to
perform
one
or
more
of
the following operations:
• perform an extra preliminary measurement so that the gain
of
the amplifier can
be adjusted (see Steps 3 and 5 in Section 2.4);
• allow the infra-red light source to warm up;
• allow the pump to run
for
a longer period
of
time when the
air-filter
is nearly
blocked. This ensures that there is a complete change
of
the
air
in the cell
between gas measurements.
Start
of
Start
of
one measurement next measurement
I I
I I
I I
~
Time
for
one------'
1
r---
measurement
.....-1
I r4
1--
____
Time between
____
----+~
111
1
measurement
I I I
I
~~,.......__~
--------+-1
r;~e
___.
o 45s 55s
~Minimum
time~
for
one measurement 1
L_
Maximum time
_j
1
for
one measurement l 872006
Fig. 2.4.
The
relationship between time
for
one gas measurement,
time between gas measurements
and
the "frequency"
of
gas
measurements
This means that the time between the
start
of
one measurement and the
start
of
the next
is not a constant
parameter
and therefore
it
is
not
possible
to
refer
to
the "frequency"
of
gas measurements (i.e. the number
of
measurements which are
performed
per
hour).
Fig. 2.4 illustrates this point. The time between measurements is, however, a constant
quantity, and
it
is therefore this
parameter
which is used
to
control the rate at which gas
measurements are
performed
when the 1306 is operating in its normal mode.
2.5. OPERATING MODES
The 1306 can operate in
four
different modes: normal, intensification, alarm and
power-
down modes. These operating modes are described in Chapter 1
of
this manual.
2.6. START
-UP
SEQUENCE
OF
THE 1306
2.7.
SELF-
TESTS
When the 1306 is supplied with
power
it
performs
a
start-up
sequence. The 1306 also
performs
a
start-up
sequence when
it
has been "reset". The
conditions
which cause the
1306
to
"reset"
are given in Section 2.8. During a
start-up
sequence the following
tasks
are performed:
1. The processor system is checked and the results
of
the last gas- and self-test
measurements made by the 1306 are deleted from its memory. If any faults are
detected in the
processor
system, the 1306 will indicate the fault by setting the
software flag
to
"1"
in its status
report
(see Section
2.1
0).
2.
A hardware test is
performed
if this test has been enabled (i.e.
if
switch no. 2
of
the upper bank
of
switches in the 1306 has been set
to
"1" -see Volume 2
of
the Instruction Manual
for
the 1306
for
details). This test checks that the
chop-
per, infra-red light source, air pump and valves are functioning correctly.
3.
If the hardware test described above shows the 1306
to
be functioning correctly,
the 1306 will
start
to
perform
its self-tests in the following order:
i)
almost
continuous self-tests;
ii) regular self-tests;
iii) gas-measurement sequence self-tests.
These self-tests are discussed in detail in Section 2.7.
If, during the
start-up
sequence described above the 1306 is found
to
be functioning
correctly, it will
perform
a gas measurement and
air-humidity
measurement and then
continue
to
operate in normal, intensification
or
alarm
mode
until such time as either (1)
an
operating
error
causes
it
to
operate
in its
power-down
mode,
or
(2) the user
com-
mands it
to
change its
mode
of
operation
(see Section 2.9.3).
However,
if
during the
start-up
sequence, a fault is detected which makes it impossible
for
the 1306
to
measure gas
concentrations
accurately, the 1306 will automatically
go
into its
power-down
mode, and
report
the operating fault in its status
report
(see Section
2.10).
The
primary
task
of
the 1306 is
to
measure the concentration
of
gas in its analysis cell.
However, this is not the only task which the 1306 performs. It also
performs
a
compre-
hensive series
of
self-tests and environmental measurements. The results
of
these self-
9
10
tests and measurements are summarised in a report called a status report (see Section
2.1
0).
Each time measurement results are requested from the 1306 they are sent together
with this report. This allows the user to evaluate the 1306's performance and
judge
the
quality
of
the gas measurements
it
performs.
There are three main series
of
self-tests:
1.
Almost continuous tests -these tests are performed whenever the 1306 is not
performing any other test
or
measurement. They check the software and
pro-
cessing system
of
the 1306, check that the temperature and power supply
to
the
1306 are within operational limits, and measure vibration noise in the analysis
cell (see Section 2.7.1).
2.
Regular tests every
30
min -these check
most
of
the electrical and mechanical
parts of the 1306 (see Section
2.
7
.2).
3.
Gas-measurement sequence tests performed during each gas-measurement se-
quence -these check the components most vital to the measurement proce-
dure (see Section 2.7.3).
The frequency with which each series
of
self-tests is performed is dependent upon the
operating mode
of
the 1
~06.
Table
2.1
illustrates how frequently each series
of
self-tests
is performed during each operating mode.
In
Fig. 2.5 this dependency is represented in
graphical form -where,
for
the purpose
of
illustration a
"time
between measurements"
of
10minutes has been chosen.
Normal
Mode
of
Operation
on
Intensification
Mode
Alarm
Mode
150 160 170
Key:
-Gas-measurement sequence self-tests
II
Regular self-tests
~
Almost continuous self-tests
180 190
High gas
concentration
measured here
Alarm Level
gas concentration
measured here
200 210
872011
Fig. 2.5. Frequency
of
the self-tests during the various operating
modes
of
the 1306
Self-tests Normal Intensification Alarm Power-down
Mode Mode Mode Mode
Almost performed performed
performed less often performed
continuous between all between all than in other continuously
self-tests other tests other tests operating
modes
Regula.t every every every not
self-tests
30
min.
30
min.
30
min. performed
with the same with the same with the same
Gas-measure- frequency as frequency as frequency as
not
ment sequence gas measure- gas measure- gas measure performed
self-tests ments ments ments
T01641
GB
O
Table
2.
1.
"Frequency"
of
the self-tests during different operational modes
2.7.1. Almost Continuous Self-tests
This series
of
tests is performed almost continuously whenever the 1306 is not
perform-
ing any other measurement-
or
self-testing sequence. This series
of
tests is the only one
which is performed when the 1306 is operating in power-down mode (see Section 2.5)
because the performance
of
these tests does not consume
too
much power.
The following tests are included in this series:
Power supply
The voltage supply to the 1306 is measured after the input filter
of
the 1306. The input
filter circuitry protects the 1306 from electromagnetic pulses and transient pulses on the
power supply -e.g. caused by lightning strikes. If the voltage supply to the 1306 does
not lie between 8,3 V and
15
V,
gas measurements are not performed and the status
report will indicate the fault.
Two kinds
of
power failure are detected by the 1306. The
first
is where theinput voltage
drops
below 8,3V but not below 7,5
V;
and the second is where the input voltage drops
below 7,5
V.
The way in which the 1306 responds to each
of
these situations is described
below.
1.
If the input voltage to the 1306 falls below 8,3 V but not below 7,5
V,
the Power
supply failure will be indicated in the status report and the 1306 will
stop
per-
forming gas measurements.
As soon as the input voltage supply to the 1306 is restored to a value above
9,3 V the 1306 will automatically resume its measurement and self-testing se-
quences -starting up where it left
off
-and the power failure will no longer
be indicated in the status report.
2.
If the input voltage to the 1306 falls below approximately 7,5 V there will no
longer be enough power to either perform gas measurements
or
to allow the
micro-processor
in the 1306 to function. The computer will therefore no longer
be able to communicate with the 1306.
11
12
When the input voltage supply
to
the 1306 is restored
to
a value above 9,3 V the
1306 will
perform
its
start-up
sequence (that is,
it
automatically "resets" itself)
before starting to take gas measurements. Users will have
to
initiate
communi-
cation
with the 1306 after this type
of
power
failure before gas-measurement
results can be requested from the 1306. The status
report
received with gas-
measurement results will only indicate that the 1306 has
"reset"
itself (the
power-failure will not be indicated).
Users can find out whether the "reset"
of
the 1306 was caused by this type
of
power
failure by referring
to
Section 2.8.
Temperature
A temperature sensor located within the analysis cell measures the temperature
of
the
cell. If this temperature lies below
-20°C
or
above +70°C, the 1306
stops
performing
gas measurements and indicates the fault in the status report.
Normally the infra-red light is switched
off
between gas measurements, but if the
tem-
perature sensor measures a temperature below
-5°
C the 1306
does
not switch
off
its
infra-red light source between measurements. The heat produced by the
infra-red
light
source will keep the
temp~rature
of
the 1306 as high as possible above
ambient
tem-
peratures, so that it can continue operating
for
as long as possible in extremely cold
environments.
Monitor's
Lid
A lever located between the
monitor
and its lid, activates a
micro-switch
if the lid is
removed. If the
micro-switch
is activated it is indicated in the status report.
Switch Settings
The 1306 "reads" the settings
of
both its
upper
and lower banks
of
switches. Details
of
these switches and their functions are provided in Section
2.1
in Volume 2
of
the Instruc-
tion Manual
for
the 1306. The user can request
to
read the settings
of
these switches be
requesting the Measurement Test Data
block
from the 1306 (see Sections 2.9.2 & 4.4.3
of
this Manual).
• By reading the setting
of
Switch 1 on its
upper
bank
of
switches the 1306 can find
out
whether it has been "reset" (see Section 2.8).
• By reading the setting
of
switch 2 on its
upper
bank
of
switches the 1306 can find out
whether it has
to
perform
the "hardware test" during its
start-up
sequence (see Sec-
tion 2.6). If this switch is set
to
"1"
(open) the hardware test is included in the
start-up
sequence. If this switch is set
to
"0" (closed) the hardware test is
not
included in the
start-up
sequence.
Vibration Noise
This is the noise measured in the analysis cell when the infra-red light source and the
mechanical
chopper
are both switched off. Under these
conditions
any noise measured
in the cell will be mainly due
to
the
air
"splashing" against the cell walls if the 1306 is
vibrating on its mast,
for
example, during a storm.
It is only vibration noise with a frequency around
20Hz
(the
chopper
frequency) which
has any real influence on the signals measured in the cell during a gas-measurement
sequence. If the 1306 is mounted on a stable mast which does
not
resonate
at
a fre-
quency around 20Hz, the
vibration-noise
signal will normally
not
contribute
significantly
to
the signals measured in the cell during a gas-measurement sequence Usually the
vibration
noise
in
the cell does not
contribute
more than a few
microvolts
to
the mea-
sured signals.
The total signal measured during a gas-measurement sequence is therefore
not
compen-
sated
for
vibration
noise. However, if this
vibration
noise is found
to
be greater than half
the total signal measured during a gas-measurement sequence, it will be indicated in the
status
report
(see background noise flag in Section
2.1
0.1
).
The user is thereby made
aware that the measured gas concentration is
artificially
high due
to
a
significant
con-
tribution
from either
vibration
noise
or
chopper
noise. If you are interested in finding out
to
what extent the
vibration
noise has interfered with the measurement
of
gas
con-
centration, you can request Measurement Test Data from the 1306 (see Section 2.9.2 &
4.4.3).
In
this data the Vibration real value (in volts) is the signal produced by
vibration
noise in the cell, and the
Raw
gas value (in volts) is the total signal measured in the cell
with the infra-red light on.
Processing System
and
Software
The 1306 checks its own processing system and software. If it finds any errors
it
will
stop
performing
gas measurements and automatically
"reset"
itself before going into a
power-down
mode
of
operation. This means that when measurement data is requested
the status
report
which accompanies it will indicate the software
error
and the reset.
2.7.2. Regular Self-tests
These tests are
performed
every
30
minutes during the normal, intensification and alarm
modes
of
operation
of
the 1306. During these self-tests
most
of
the electrical and
me-
chanical parts
of
the 1306 are checked. If any mechanical
component
is found
to
be
functioning incorrectly the 1306 will repeat the test on the faulty
component
almost
immediately. If the fault is still present, the 1306 will indicate the type
of
fault in its
status
report
and
stop
taking gas measurements.
After
30
minutes the 1306 will
perform
its regular tests again. If the 1306 still detects the fault, the test on the faulty
component
will be repeated almost immediately. If the fault is no longer detected, the 1306 will
remove the fault indication in it_s status report, and start
performing
gas measurements
and self-tests automatically again; but if the fault is still present, the indicated fault will
remain in its status
report
and the 1306
stop
taking gas measurements.
Regular tests can be divided up into the following groups:
1.
Pnuematics tests -
to
check the air-shunt and
air-filter
are not blocked and that
the pump and the valves are functioning properly.
2.
Microphone(s) and preamplifier(s) tests -these tests check that the microphones
and their associated preamplifiers are functioning correctly.
3.
Analogue to digital converter test -checks that the analogue
to
digital
converter
is functioning correctly.
4.
Chopper test -checks that the mechanical
chopper
is balanced.
These tests are described in detail below.
1.
Pnuematics Tests:
Air-filter
With both the inlet and outlet valves open (see Fig. 2.6), the
pump
is started and the
pressure difference across the pump is measured. Using this value the 1306 can calcu-
late
how
long the pump must run to ensure that the analysis cell is completely flushed
13
14
Infra-Red
Source
Humidity
Lamp
Optical Window )
(Air
Shunt
Inlet
Valve (1)
Fine Air-Filter
Coarse
Air-Filter
870411
Fig.
2.
6.
The measurement system
of
the 1306
before starting a new gas measurement. If this pressure difference is outside operational
limits it indicates that either the
air-filter
is blocked
or
that the fine
air-filter
has
not
been mounted correctly and the user is given a warning in the status
report
(see Sec-
tions
2.1
0.
& 4.4.3.
for
further details).
Pump/Inlet Valve
While the
pump
is running, the inlet valve is closed and the pressure difference across
the
pump
is measured. If this pressure is
too
low
it indicates that either the
pump
or
the
inlet valve is faulty.
In
this
condition
the 1306 is unable
to
perform
reliable gas measure-
ments so
it
stops
performing
gas measurements, and reports the detected fault in the
status report.
Pump/Outlet Valve
The
pump
is stopped, then the inlet valve is opened and the outlet valve is closed and
the
pump
is started up again. The pressure difference across the
pump
is measured. If
it
is
too
low
it
indicates that either the pump
or
the outlet valve is faulty.
In
this
condition
the 1306 is unable
to
perform
reliable gas measurements so it
stops
performing
gas
measurements, and reports the detected fault in the status report.
Air-shunt
The
pump
is stopped abruptly, and during the
first
second after the
pump-stop
the
decrease in pressure across the air-shunt is measured. If this decrease is less than half
the pressure measured in the
Pump/Outlet
Valve test described above, it indicates that
the air-shunt is blocked. The user is given a warning in the status report.
Pressure Transducer Offset
With both the inlet and outlet valves open the pressure
transducer's
offset
value is read.
This value is used
to
correct
all measurements made by the pressure transducer.
Table of contents
Popular Gas Detector manuals by other brands
Honeywell Home
Honeywell Home resideo CO8MS manual
Tecnocontrol
Tecnocontrol SE126K user manual
PEMTECH
PEMTECH PT2008 Series Operator's manual
Atest Gaz
Atest Gaz SmArtGas 4 user manual
S+S Regeltechnik
S+S Regeltechnik AERASGARD RCO2-A NT operating instructions
Consilium
Consilium Salwico ST400 H2S Calibration instructions
