Eaton Crouse-hinds series User manual

K1550
MTL gas analyser
February 2017
INM MTL 130-0031 Rev 14
Instruction manual
MTL gas analysers & systems

ii INM MTL 130-0031 Rev 14
DECLARATION OF CONFORMITY
A printed version of the Declaration of Conformity has been provided separately within the original shipment of
goods. However, you can find a copy of the latest version at -
http://www.mtl-inst.com/certificates

INM MTL 130-0031 Rev 14 iii
CONTENTS
DECLARATION OF CONFORMITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
1 INTRODUCTION ....................................................................1
1.1 Manual symbols ...........................................................................1
1.2 Information ...............................................................................1
2 SPECIFICATION.....................................................................2
2.1 Display...................................................................................2
2.2 Ranges...................................................................................2
2.3 Accuracy .................................................................................2
2.4 Repeatability ..............................................................................2
2.5 Stability ..................................................................................2
2.6 Sample flow ..............................................................................2
2.7 Sample pressure...........................................................................2
2.8 Sample condition ..........................................................................2
2.9 Sample connections........................................................................2
2.10 Speed of response .........................................................................2
2.11 Analogue outputs ..........................................................................2
2.12 Alarm outputs .............................................................................2
2.13 Environmental conditions ...................................................................3
2.14 Power supply .............................................................................3
2.15 Dimensions & mounting ....................................................................3
2.16 Enclosure material and protection ............................................................3
3 INSTALLATION .....................................................................4
3.1 Unpacking and visual checking...............................................................4
3.2 Siting ....................................................................................4
3.3 Electrical connections ......................................................................4
3.4 Installation requirements for EMC ............................................................4
3.4.1 Routing of wires ...........................................................................4
3.5 Sampling and piping .......................................................................4
3.6 Sensor and control/display-unit connections ...................................................6
3.6.1 Keyboard .................................................................................6
3.6.2 Control/display unit connections .............................................................9
4 OPERATION.......................................................................10
4.1 Controls and indicators ....................................................................10
4.2 Keyboard ................................................................................10
4.3 Alarm LEDs ..............................................................................11
4.4 Initialization..............................................................................11
4.5 View mode ..............................................................................12
4.6 Edit mode ...............................................................................13
4.7 Calibration Gas and Analogue Output Ranges .................................................13
5 CALIBRATION ....................................................................15
5.1 General .................................................................................15
5.2 Piping...................................................................................15
5.3 Calibration Gas Level ......................................................................15
5.4 Calibration method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
5.5 Compensation calibration ..................................................................18
5.6 Entering calibration mode ..................................................................18
5.7 Lower point calibration ....................................................................18
5.8 Upper point calibration ....................................................................18
6 SERVICING .......................................................................12

iv INM MTL 130-0031 Rev 14
THIS PAGE IS LEFT INTENTIONALLY BLANK

INM MTL 130-0031 Rev 14 1
1 INTRODUCTION
The K1550 instrument is a MTL gas analyser that can be used for measuring the concentration
of a variety of gases using a thermal conductivity sensor (commonly called a katharometer).
A microprocessor is used to control the instrument and its associated digital circuitry to provide
a highly advanced, highly featured, user-friendly gas analyser. Gases whose concentration can
be measured include- carbon dioxide, helium, hydrogen, argon, neon and some Freons.
Versions of the analyser are available that enable the instrument/sensor to be located within a
flammable hazardous area.
1.1 Manual symbols
The following methods are used in this manual to alert the user to important information:-
WARNING
Warnings are provided to ensure operator safety and MUST be followed.
CAUTION
A Caution is provided to prevent damage to the instrument.
NOTE
These are used to give general information to ensure correct operation
1.2 Information
Waste Electrical and Electronic Equipment directive (WEEE) 2002/96/EC
(RoHS) directive 2002/95/EC
WARNING
This equipment must only be used in accordance with the manufacturer’s
specification, instructions for installation, use and maintenance to ensure that
the protection of the operator is not impaired. It is the responsibility of the
installer to ensure the safety and EMC compliance of any
particular installation.

2INM MTL 130-0031 Rev 14
2 SPECIFICATION
2.1 Display
Dot Matrix LCD showing 2 or 4 lines of alphanumeric characters
2.2 Ranges
Carbon dioxide, argon, neon, methane, Freon: 0–20%, 0–100% or 80–100%
Hydrogen or helium: 0–5%, 0–20%, 0–100%, 80–100% or 95–100%
Consult your local MTL Gas sales office for other gases and ranges.
2.3 Accuracy
±2% f.s.d. depending upon span and gas
2.4 Repeatability
Better than 1% of f.s.d.
2.5 Stability
<1 % f.s.d./month
2.6 Sample flow
100 to 300 ml/min for optimum performance
2.7 Sample pressure
Absolute maximum 6 bar
The pressure applied to the cell is determined by the vent pressure which should be atmospheric
for quoted accuracy
2.8 Sample condition
Must be non-condensing and free of particulates
2.9 Sample connections
Inlet and outlet 0.25” (suitable for 6mm) diameter tube. Both ports are fitted with captive seal
compression fittings.
2.10 Speed of response
(T90): 20 secs typical
2.11 Analogue outputs
4 to 20mA
Programmable on most models to between 100% and 20% of the full scale of the
analyser. For instruments scaled from zero – e.g. 0 to 100%, 0 to 20% etc. the 20mA
point is programmable. For instruments with a live zero- e.g. 80 to 100%, the 4mA point is
programmable – see Section 5.7
Maximum load on current output- 600 ohms
2.12 Alarm outputs
2 alarms each, user programmable for:
Mode - HIGH, LOW or OFF
Level - over full display range of instrument and
Hysteresis - 0% to 10% of set point.
Volt free, change-over contacts rated at 30V ac or dc, 1A, - normally energised

INM MTL 130-0031 Rev 14 3
2.13 Environmental conditions
Ambient operating temperature range
Sensor: –10°C to 40°C
Electronics: 0°C to 40°C
(0-90% RH non-condensing)
Storage temperature range
–5°C to +55°C, (0-90% RH non-condensing)
Altitude
Up to 2000m
Pollution degree
Pollution degree 2
2.14 Power supply
(110 to 120V) or (220 to 240V) 50 or 60 Hz. 12VA maximum.
2.15 Dimensions & mounting
Electronics/display unit - panel mounting case with two clamps (see Figure 1)
Remote sensor - (see also Figure 3)
Smaller enclosure- Overall size: 200 (w) x200 (d) x 103 (h)
Larger enclosure- Overall size: 230 (w) x 205 (d) x 103 (h)
2.16 Enclosure material and protection
Electronics/display unit
Glass-fibre reinforced Noryl. When panel mounted (rear of instrument not exposed) IP40.
IP30 otherwise.
Remote sensor housing
Grey polycarbonate

4INM MTL 130-0031 Rev 14
3 INSTALLATION
3.1 Unpacking and visual checking
Take all standard precautions when opening packages. In particular avoid the use of long
bladed cutters. Search packing before discarding it to ensure that all of the components have
been removed. Check that all pipe connections have captive seal nuts.
3.2 Siting
The instrument is designed to be panel mounting. See Figure 1 for details of the aperture
dimensions, etc.
3.3 Electrical connections
Three plug-in terminal blocks are provided at the rear of the instrument. See labels for details.
WARNING
This instrument must be installed with a disconnecting switch close to it,
within easy reach of the operator and compliant with the relevant parts of
IEC 60947-1 and IEC 60947-3. It must be marked to indicate this function
and show ON and OFF positions. Wiring should conform to local codes. Only
the live conductor has an internal equipment fuse. European regulations
recommend that fuses be fitted in both the live and neutral of the mains
supply to the instrument.
NOTE
The Relay operation and labelling ‘Normal’ relates to process normal and not the electrical
rest position of the relays, In process normal the relays are energised.
3.4 Installation requirements for EMC
To ensure compliance with the European EMC directive certain installation precautions are
necessary as follows:
3.4.1 Routing of wires
To minimise the pick-up of electrical noise, all signal wiring should be shielded and routed away
from power cables.
3.5 Sampling and piping
The standard connections are captive seal compression fittings suitable for 0.25” (or 6mm
diameter tube on the sample inlet and sample outlet.
NOTE
Optimum analyser performance is achieved with the flow rate specified in Section 3.6.
Consider also installing pipe work for a calibration gas inlet - this avoids the need to remove
the sample connection when connecting a calibration gas. It is much more convenient to
have a ‘T’ piece and valves installed permanently in the sample feed lines.

INM MTL 130-0031 Rev 14 5
Figure 1- General layout
Figure 2- K1550 in EEx d enclosure
145
8
Panel cutout
90 x 138 (+1/–0)
96
144
Dimension in mm
AL1 AL2 AL1 AL2
OXYGEN CARBON DIOXIDE
HITECH INSTRUMENTS
Luton England. LU4 9UR
KG 1550 Gas Analyser
View Edit
Calibrate Measure
Cal Gas
View Edit
Cal
Meas
Cal
Gas
KG1550 MTL Gas analyser
AL1
AL2
2.5% H
2
MTL
Hazardous
area tmnls
1
2
34
MTL
Hazardous
area tmnls
1
2
34
MTL
Hazardous
area tmnls
1
2
34
MTL
Hazardous
area tmnls
1
2
34
View Edit
CalMeas
Cal
Gas
HITECH INSTRUMENTS
Luton England.
AL1 AL2 AL2AL1
98.5 H2 %
K1550 Gas Analyser
18
AL1 AL2 AL1 AL2
OXYGENCARBON DIOXIDE
HITECH INSTRUMENTS
LutonEngland. LU4 9UR
KG 1550 Gas Analyser
View Edit
Calibrate Measure
Cal Gas
View Edit
Cal
Meas
Cal
Gas
KG1550 MTL Gas analyser
AL1 AL2
98.5% H
2
View Edit
Cal
Meas
Cal
Gas
Tapped M20 entries
Tapped M20 entry
82
270
318
Ø14
310
353
490
65 50
50 50 55
270
98
20
Dimensions in mm

6INM MTL 130-0031 Rev 14
3.6 Sensor and control/display-unit connections
CAUTION
The sensor and control unit are matched during manufacture. Each instrument will operate
correctly only with its own sensor. The sensor serial number is recorded on the test
certificate supplied with the instrument.
3.6.1 Keyboard
The connections for the sensor are located inside the sensor enclosure on the circuit-board
backplane, adjacent to the cable entry gland. The connections SIG, REF and COM correspond
to the same connections on the rear of the control/display unit and should be wired
accordingly.
NOTE
These are used to give general information to ensure correct operation
Figure 4 shows the connections between the sensor unit and the control panel for safe
environments where potentially explosive atmospheres will NOT be encountered.
Figure 5 shows details of connections for installations where the control unit is mounted in a
non-hazardous environment but the sensor has to be located in a hazardous area, i.e. where
there is a known risk of a potentially explosive atmosphere being encountered.
Figure 6 shows the internal wiring connections for a “flameproof” Ex d enclosure where the
electronic control unit also needs to be mounted in the hazardous area.
WARNING
For hazardous area installations it is particularly important that the installation
of the shunt diode safety barriers comply fully with the appropriate
requirements. Details of these requirements are supplied with the barrier
units. When the remote sensor is not installed in a hazardous area, the safety
barrier is not required.
NOTE
Some differences between sensors, enclosures, and their internal structure (e.g. plastic or
stainless steel piping) will be encountered depending upon the type specified, however, this
will have no effect upon the wiring connections.
Figure 4- Connections for installation in non-hazardous area
REAR VIEW OF P
ANEL
COM
REF
SIG
REMOTE SENSOR
SEN
Shown not passing through
cable gland for clarity
Sample
outlet Sample
inlet
Sample Flow
Adjustment
REMOTE SENSOR UNIT
Sensor cable screen
13
14
15
16
17
N
-
MAINS
120-0384-2
E
L
+
4/20mA
C
6
5
4
3
2
1
NC
NC Alarm 2
Alarm 1
NO
NO
C

INM MTL 130-0031 Rev 14 7
Figure 3a- Enclosure- nylon piping version
Figure 3b- Enclosure- stainless steel piping version
113.5
163.5
180
20
130
200
120-0308-6
MTL Gas analyser
remote sensor
Luton, England
Hitech Instruments Ltd. 260-0170 issue 1
PL2
REF COM SIGBLUE
RED GREEN
PL1
REF COM SIG
GREEN
BLUE
RED
180
180
25
Dimensions in mm
163.5
163.5
50
120-0308-6
MTL Gas analyser
remote sensor

8INM MTL 130-0031 Rev 14
Figure 5- Connections when sensor is in a hazardous area
Figure 6 - Internal wiring for K1550FX model mounted in a hazardous area
WARNING
All wiring for the K1550FX flameproof enclosure must enter the enclosure
through suitably certified M20 cable glands in order to maintain the
certification of the enclosure.
3.6.2 Control/display unit connections
REAR VIEW OF PANEL
MTL
766P
Hazardous
area tmnls
1
2
34
COM
REF
SIG
REMOTE SENSOR
Shown not passing through
single cable gland for clarity
Sample
outlet
CT
I
S E
Hazardous
area tmnls
Sample
inlet
Sample Flow
Adjustment
Hazardous area Safe area
REMOTE SENSOR UNIT
Sensor cable screen
13
14
15
16
17
N
-
MAINS
120-0384-2
E
L
+
4/20mA
C
6
5
4
3
2
1
NC
NC Alarm 2
Alarm 1
NO
NO
C
Haz ardous
area tmnls
34
Common Signal Reference
To Katharometer
120-0431-1
17
18
16
4
3
2
1
6
5
20
19
Live Neutral
Earth
Alarm1 NO
Alarm 1 C Alarm 1 NC
Alarm 2 NO
Alarm 2 C
Alarm 2 NC
4/20mA + 4/20mA -
120-0430-2
IP65 Keyboard Box containing
“Simple Apparatus” Switches
Ex d IP66 Cable Path
Hazardous
Area Wiring
Non-Hazardous
Area Wiring
MTL766Pac
5
Wires
View Edit
Cal
Meas
Cal
Gas
17
18
16
4
3
2
1
6
5
20
19
8
Wires
3 x
MTL758+
View Edit
CalMeas
Cal
Gas
HITECH INSTRUMENTS
Luton England.
AL1 AL2 AL2AL1
98.5 H2
%
K1550 Gas Analyser
Connect to
Intrinsically
Safe Earth
MTL
Hazardous
area tmnls
1
2
34
MTL
Hazardous
area tmnls
1
2
34
MTL
Hazardous
area tmnls
1
2
34
MTL
Hazardous
area tmnls
1
2
34
AL1 AL2 AL1 AL2
OXYGEN CARBON DIOXIDE
HITECH INSTRUMENTS
Luton England. LU4 9UR
KG 1550 Gas Analyser
View Edit
Calibrate Measure
Cal Gas
View Edit
Cal
Meas
Cal
Gas
KG1550 MTL Gas analyser
AL1 AL2
98.5% H
2

INM MTL 130-0031 Rev 14 9
The connections for the control/display unit are located on the rear of the case - with the
exception of the K1550FX model which has the connections provided at DIN-rail mounted
terminals.
WARNING
AC mains power (115 or 230V AC) is required to power the K1550 control/
display unit. Ensure that supplies are isolated at some external point before
working on connections to the unit.
CAUTION
Check the supply voltage rating of the control unit before connecting it to the AC power
source. The unit will be damaged by the application of a voltage exceeding the specified
range.
Figure 7a shows the standard connections provided at the rear of the K1550, including the
4/20mA analogue output (terminals 16 & 17), the alarm outputs (terminals 1-3 and 4-6) and the
AC power inputs (13-15).
Figure 7b shows the additional connection points (terminals 20-21) for a 4/20mA compensation
signal from an external instrument.
AC power signals should be kept apart from the input signal cabling, as much as possible, to
avoid potential interference and any hazard from the high voltage cabling.
In normal operation (i.e a non-alarm state) the alarm relays are energised, providing continuity
between the ‘C’ and ‘NC’ terminals.
13
14
15
16
17
18
19
20
21
N
-
-
MAINS
120-0344-3
E
L
+
+
Not used
4/20mA
C
6
5
4
3
2
1
NC
NC Alarm 2
Alarm 1
NO
NO
C
Input
4/20mA
Compensation
13
14
15
16
17
N
-
MAINS
120-0384-2
E
L
+
4/20mA
C
6
5
4
3
2
1
NC
NC Alarm 2
Alarm 1
NO
NO
C
Figure 7a- Standard connections Figure 7b- Connections with compensation input

10 INM MTL 130-0031 Rev 14
K1550FX model mounted in a hazardous area
Connections to this display/control unit are provided on DIN-rail mounted terminals to the left
of the display. Terminal identities are provided on a label below them- see Figure 8.
M20 threaded holes are provided in the front wall of the flameproof enclosure for these
connections- see Figure 2. They must be fitted with appropriately certified cable glands or
similarly approved blanking plugs for any unused ones.
Only one cable can be passed through a cable gland, so four holes are provided to
accommodate:
• AC power
• 4/20mA analogue output signal
• Alarm 1
• Alarm 2
Figure 8- K1550FX terminals
4 OPERATION
4.1 Controls & indicators
See Figure 1 for details of the front panel.
4.2 Keyboard
The front panel has the following buttons.
Button Purpose
View used to display and edit the alarm output and
calibration levels
used in the editor
used in the editor
Edit used in the editor
Cal used to enter calibration mode
Meas Cal. Gas used to trigger a measurement in calibration mode
17
18
16
4
3
2
1
6
5
20
19
Live Neutral
Earth
Alarm1 NO
Alarm 1
CAlarm 1 NC
Alarm 2 NO
Alarm 2 C
Alarm 2 NC
4/20mA
+ 4/20mA –
120-0430-2

INM MTL 130-0031 Rev 14 11
4.3 Alarm LEDs
Two LEDs are fitted, one for each alarm. The LEDs are ON when the alarm is active and OFF
when the alarm is ‘normal’.
4.4 Initialisation
When the instrument is switched on the display will show :-
- where #### is the part No. of the software and x.x is the software version.
This display will remain for a few moments while the instrument goes through its initialisation
program, after which it will change to measurement mode and display the measured values -
see Figure 9.
Figure 9a- Standard display Figure 9b- Display with compensated input
In measurement mode the display, alarm LEDs, alarm relays and the analogue output are
continually updated with the latest measured values. If an alarm level is exceeded then the
appropriate relay will be de-energised and the Alarm LED lit.
In measurement mode, only the “View” and “Cal” buttons are active. Before activating either
of these functions study the following sections.
Hitech K1550
Gas Analyser
S/W = ####-x.x
Initialising
Uncorr. H2 5.2%

12 INM MTL 130-0031 Rev 14
4.5 View mode
This mode is entered by pressing the “View” button. In view mode all user defined values and
the instrument data are displayed in a series of screens. The edit mode may also be entered, in
which it is possible to change the settings. The screens are shown in the following diagram.
Screen 5 (in diagram above) will vary depending on whether the low scale value or the upper scale
value is programmable.
The arrow pointer on the left-hand side indicates which line may be edited. The “ ” or “ ” buttons
are used to move the arrow to the appropriate line. Scrolling downwards from the bottom line moves
the display onto the next screen. Similarly scrolling upwards from the top line moves the display to
the previous screen.
View mode may be left at any time by pressing the “View” button. The instrument will then return to
measurement mode and display the measured concentrations.
Summary: View mode (block cursor not displayed):-
advances to the next entry
returns to the previous entry
View exits view mode - Returns to Measurement mode
Edit A warning screen is displayed and the edit cursor is displayed if Edit is repressed.
See below
Press
5
Measurement
Mode
Screen
View
1
2
43
Alarm 1
Level = xxxx%
Hyst = yyy%
Mode = zzz
Calibration He
Level = xxx%
20mA O/P
20mA = xxxx
Alarm 2
Level = xxxx%
Hyst = yyy%
Mode = zzz
Sample = He in Air
Range = 0/100%
O/P = 4/20mA Prog

INM MTL 130-0031 Rev 14 13
4.6 Edit mode
Any value may be changed by moving the arrow pointer to the appropriate line and pressing
the “Edit” button. When the “Edit” button is pressed from view mode the following screen is
displayed.
NOTE:
The operator should now ensure that continuing will not cause any plant malfunction or
safety problems, due to locking of the outputs.
When edit mode is entered, a flashing cursor will appear on the first digit that may be altered.
Use the “ ” or “ ” buttons to increment or decrement the digit, then press the “Edit” button
to move on to the next digit. If a digit does not require a change, press the “Edit” button to
move to the next. When the “Edit” button is pressed on the final digit, the display will show
‘Storing Data’ momentarily and then return to view mode, displaying the new parameters.
NOTE:
When setting alarms the maximum hysteresis that can be set is 10% of the span of the
particular channel. It is important not to set the hysteresis to a level greater than the alarm
point otherwise the alarm will never reset.
Summary: Edit mode (block cursor displayed):-
increments the digit under the cursor
decrements the digit
View exits edit mode - Returns to View mode
Edit advances to the next digit, or stores the entry if the last digit has been changed.
The cursor is then switched off - see above.
4.7 Calibration Gas and Analogue Output Ranges
The following tables show the ranges available for editing the analogue output and
calibration gases:-
WARNING Outputs
will freeze
VIEW to escape
EDIT to continue

14 INM MTL 130-0031 Rev 14
‘ZERO START’ MODELS
‘LIVE ZERO
’ MODELS
95 – 100% models
95% 100%
4mA
99%
20mA
Analogue output range
Calibration gas concentration range
Set lower limit in this range
80 – 100% models
80% 100%
4mA
96%
20mA
Calibration gas concentration range
Analogue output range
Set lower limit in this range
0 – 20% models
0% 20%
4mA
4%
20mA
Analogue output range
Calibration gas concentration range
Set upper limit in this range
0 – 5% models
0% 5%
4mA
1%
20mA
Analogue output range
Calibration gas concentration range
Set upper limit in this range
0% 100%
4mA
20%
20mA
0 – 100% models
Calibration gas concentration range
Analogue output range
Set upper limit in this range

INM MTL 130-0031 Rev 14 15
5 CALIBRATION
5.1 General
The katharometer based analysers are extremely stable instruments and require only very
occasional calibration. The exact calibration period depends on the type of sample and the
environment in which the instrument is placed. In practice it is unlikely that check periods
of less than one month will be necessary, and three to six months will be found to be more
appropriate. It is also recommended that quality assurance procedures for the instrument
should be written to allow verification as opposed to calibration. Verification involves
checking that the instrument provides a correct analysis of a “standard” gas within the limits
of the instrument; calibration should then be carried out only when a result is produced that
is outside of those limits. The frequency of the verification would need to be in line with the
quality regime being operated by the user.
NOTE
The instrument ‘freezes’ the analogue output and the alarms while it is being calibrated,
so any control loops connected to the instrument should be disabled before proceeding.
Calibration mode can only be entered by pressing the “Cal” button for approximately 5
seconds.
WARNING
Ensure that the process is in a safe state and that the exhaust of the standard
gas is vented to a safe area.
5.2 Piping
The piping carrying the calibration gas must not have any leaks. The flow of this gas must be
controlled and should be approximately the same as the flow rate of the sample experienced
during normal process use. Metal piping is preferred as it is less prone to damage and sealing
problems.
NOTE
Pressure regulators and gauges in the calibration gas lines probably have a certain amount
of ‘dead’ space within them and will probably require purging for several minutes before the
delivered gas matches that of the cylinder contents.
Hint: Keep the instrument in measurement mode while purging. When the reading
becomes steady, the dead space can be assumed to have been purged.
5.3 Calibration Gas Level
A full calibration requires two standard gases. These gases are referred to as ‘lower’ and
‘upper’. (These names are used to avoid the possible confusion caused by calling them ‘zero’
and ‘span’ on instruments with scales not starting at zero.)
The requirement for the calibration gases depends on the configuration of the instrument. The
scales available for the K1550 fall into two types:-
• Zero scale point fixed at 0% (e.g. 0-5%) (‘Zero start’)
• Full scale point fixed at 100% (e.g. 95-100%) (‘Live zero’)
Zero start instruments require a ‘lower’ calibration gas of 0% concentration of Measurand,
and an ‘upper’ calibration gas concentration appropriate to the upper range of the instrument.
The upper value of the instrument must be set prior to calibration but the ‘lower’ value is
0%. For example, an analyser spanned 0% to 5% hydrogen in nitrogen would require a
‘lower’ calibration gas of 100% nitrogen and an ‘upper’ calibration gas of between 1% and 5%
hydrogen in nitrogen.

16 INM MTL 130-0031 Rev 14
Live zero instruments require an ‘upper’ calibration gas containing 100% of Measurand, and
a ‘lower’ calibration gas concentration of >80% of span concentration of Measurand in carrier
gas. The lower value of the instrument must be set prior to calibration but the ‘upper’ one is
fixed at 100%. For example, an analyser spanned 95% to 100% hydrogen in nitrogen would
require an ‘upper’ calibration gas of 100% hydrogen, and a ‘lower’ calibration gas of between
95% and 99% hydrogen in nitrogen.
NOTE
For optimum accuracy, if it is possible (within the constraints of the instrument and the
calibration gas suppliers), it is advisable to calibrate at a concentration most typical of those
encountered in normal instrument use.
Refer to the menu diagram in Section 5.5 and set the gas calibration level as follows:
• Press the “View” button
• Use the “ ” or “ ” arrows to move round to the entry for Calibration Gas
• Press the “Edit” button. Use the “ ” or “ ” arrows to adjust the digit, and
the “Edit” button to move to each digit in turn
• When the required level is set correctly, press the “View” button to return to the
measuring mode
NOTE
The calibration gas level should be entered before proceeding with a calibration routine.
5.4 Calibration method
‘Zero start’ instruments require that the ‘lower’ calibration point is set first and ‘live zero’
instruments that the ‘upper’ point is set first. Screen prompts are given to confirm the gas
required at the appropriate point in the calibration procedure.
NOTE
The analyser should be isolated from the process gas and the calibration gas introduced into
the analyser at the correct flow rate.
The following diagram illustrates the calibration mode screens etc.their physical condition.