GasSens
Hydrogen Sulfide
Gas Monitor
Home Office
European Office
Analytical Technology, Inc.
6 Iron Bridge Drive
Collegeville, PA 19426
ATI (UK) Limited
Unit 1 & 2 Gatehead Business Park
Delph New Road, Delph
Saddleworth OL3 5DE
Ph: +44 (0) 1457-873-318
Ph: 800-959-0299
610-917-0991
Fax: 610-917-0992
Email: sales@analyticaltechnology.com
Fax: + 44 (0)1457-874-468
Email: sales@atiuk.com
PRODUCT WARRANTY
Analytical Technology, Inc. (Manufacturer) warrants to the Customer that if any
part(s) of the Manufacturer's equipment proves to be defective in materials or
workmanship within the earlier of 18 months of the date of shipment or 12
months of the date of start-up, such defective parts will be repaired or replaced
free of charge. Inspection and repairs to products thought to be defective within
the warranty period will be completed at the Manufacturer's facilities in
Collegeville, PA. Products on which warranty repairs are required shall be
shipped freight prepaid to the Manufacturer. The product(s) will be returned
freight prepaid and allowed if it is determined by the manufacturer that the part(s)
failed due to defective materials or workmanship.
This warranty does not cover consumable items, batteries, or wear items
subject to periodic replacement including lamps and fuses.
Gas sensors carry a 12 months from date of shipment warranty and are
subject to inspection for evidence of misuse, abuse, alteration, improper storage,
or extended exposure to excessive gas concentrations. Should inspection
indicate that sensors have failed due to any of the above, the warranty shall not
apply.
The Manufacturer assumes no liability for consequential damages of any
kind, and the buyer by acceptance of this equipment will assume all liability for
the consequences of its use or misuse by the Customer, his employees, or
others. A defect within the meaning of this warranty is any part of any piece of a
Manufacturer's product which shall, when such part is capable of being renewed,
repaired, or replaced, operate to condemn such piece of equipment.
This warranty is in lieu of all other warranties ( including without limiting
the generality of the foregoing warranties of merchantability and fitness for a
particular purpose), guarantees, obligations or liabilities expressed or implied by
the Manufacturer or its representatives and by statute or rule of law.
This warranty is void if the Manufacturer's product(s) has been subject to
misuse or abuse, or has not been operated or stored in accordance with
instructions, or if the serial number has been removed.
Analytical Technology, Inc. makes no other warranty expressed or implied
except as stated above.
GasSens Gas Detection System
Section 1 - Overview
TABLE OF CONTENTS
TABLE OF CONTENTS .............................................................................................................................. 1
INTRODUCTION ...................................................................................................................................... 1-3
A11 SENSOR/TRANSMITTER ...................................................................................................................... 1-4
A14 RECEIVER MODULE ............................................................................................................................ 1-4
A17 POWER SUPPLY MODULE .................................................................................................................... 1-4
NEMA 4X ENCLOSURES ........................................................................................................................... 1-4
EXPLOSION-PROOF ENCLOSURES ................................................................................................................ 1-4
AUDIBLE HORN ......................................................................................................................................... 1-5
STROBE LAMP ........................................................................................................................................... 1-5
A19 BATTERY BACK-UP ............................................................................................................................ 1-5
MECHANICAL INSTALLATION .......................................................................................................... 1-6
ELECTRICAL INSTALLATION .......................................................................................................... 1-11
RECEIVER MODULE ............................................................................................................................. 2-1
INTRODUCTION ......................................................................................................................................... 2-1
ELECTRICAL CONNECTION......................................................................................................................... 2-1
FACTORY CONFIGURATION ........................................................................................................................ 2-3
CONFIGURATION SWITCHES ....................................................................................................................... 2-3
SETPOINT SELECTION ................................................................................................................................ 2-5
RANGE SELECTION .................................................................................................................................... 2-6
RELAY CONFIGURATION ............................................................................................................................ 2-6
EXTERNAL HORN RELAY ........................................................................................................................... 2-7
DISPLAY INTENSITY .................................................................................................................................. 2-7
OPERATION ............................................................................................................................................. 2-8
STARTUP................................................................................................................................................... 2-8
ALARM ACKNOWLEDGE AND RESET ........................................................................................................... 2-8
TROUBLE ALARM AND RELAY .................................................................................................................... 2-9
AUTO-TEST FUNCTION (OPTIONAL) ........................................................................................................... 2-9
LAMP AND HORN TEST ............................................................................................................................ 2-10
RELAY INHIBIT ........................................................................................................................................ 2-10
MANUAL AUTO-TEST .............................................................................................................................. 2-11
REMOTE RESET ....................................................................................................................................... 2-11
ANALOG OUTPUT .................................................................................................................................... 2-11
AUTO-TEST REMOTE VERIFICATION......................................................................................................... 2-12
DEACTIVATING THE AUTO-TEST FUNCTION.............................................................................................. 2-12
TROUBLESHOOTING........................................................................................................................... 2-13
RECEIVER MODULE PARTS LIST ..................................................................................................... 2-14
A17 UNIVERSAL POWER SUPPLY ....................................................................................................... 3-1
POWER SUPPLY PARTS LIST ............................................................................................................... 3-3
OPTIONAL EQUIPMENT ....................................................................................................................... 4-1
INSTALLATION .......................................................................................................................................... 4-1
OPERATION ............................................................................................................................................... 4-2
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GasSens Gas Detection System
Section 1 - Overview
REMOVAL FROM SERVICE .......................................................................................................................... 4-2
BATTERY BACKUP PARTS LIST ......................................................................................................... 4-3
STROBE PARTS LIST.............................................................................................................................. 4-3
STROBE LIGHT ...................................................................................................................................... 4-3
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GasSens Gas Detection System
Section 1 - Overview
INTRODUCTION
GasSens is an on-line monitoring system for the detection of hazardous gases in ambient
air. It is designed to detect and alarm gas leaks from storage cylinders, process piping, or gas
feed equipment in virtually any type of industrial plant environment. Systems are available for
monitoring a variety of gases as shown in Table 1-1.
TABLE 1-1
GAS
CODE NO.
Ammonia
Carbon Monoxide
Hydrogen
Nitric Oxide
Oxygen
Phosgene
15*
16*
18
25
19
20
Bromine
Chlorine
Chlorine Dioxide
Fluorine
Hydrogen Peroxide
Ozone
Iodine
10*
11*
12*
13*
34
14*
35*
Hydrogen Chloride
Hydrogen Cyanide
Hydrogen Fluoride
Hydrogen Sulfide
Nitrogen Dioxide
Sulfur Dioxide
21*
22*
23*
24*
26*
27*
Arsine
Diborane
Germane
Hydrogen Selenide
Phosphine
Silane
28
29
30
31
32
33
STD. RANGE
GENERAL GASES
0-100 PPM
0-100 PPM
0-4%
0-100 PPM
0-25%
0-2 PPM
OXIDANT GASES
0-2 PPM
0-10 PPM
0-2 PPM
0-2 PPM
0-10 PPM
0-2 PPM
0-2 PPM
ACID GASES
0-20 PPM
0-20 PPM
0-20 PPM
0-50 PPM
0-20 PPM
0-20 PPM
HYDRIDE GASES
0-1000 PPB
0-1000 PPB
0-1000 PPB
0-1000 PPB
0-1000 PPB
0-10 PPM
MIN. RANGE
MAX. RANGE
0-50 PPM
0-50 PPM
0-2000 PPM
0-25 PPM
0-10%
0-1 PPM
0-500 PPM
0-500 PPM
0-10%
0-500 PPM
0-100%
0-100 PPM
0-1 PPM
0-1 PPM
0-1 PPM
0-1 PPM
0-10 PPM
0-1 PPM
0-1 PPM
0-100 PPM
0-100 PPM
0-100 PPM
0-100 PPM
0-100 PPM
0-100 PPM
0-100 PPM
0-10 PPM
0-10 PPM
0-10 PPM
0-10 PPM
0-5 PPM
0-10 PPM
0-200 PPM
0-200 PPM
0-200 PPM
0-500 PPM
0-200 PPM
0-200 PPM
0-1000 PPB
0-1000 PPB
0-1000 PPB
0-1000 PPB
0-1000 PPB
0-1000 PPB
0-100 PPM
0-100 PPM
0-100 PPM
0-100 PPM
0-100 PPM
0-100 PPM
* Auto-Test is available in these gases.
The GasSens system consists of modular components that can be used in a variety of
configurations to fit specific application requirements. A description of the major system
components follows:
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GasSens Gas Detection System
Section 1 - Overview
A11 Sensor/Transmitter
Consists of an electrochemical gas sensor closely coupled to a NEMA 4X transmitter.
This component measures gas concentration and converts the measurement to a digital signal
for transmission to a receiver module. It must be mounted in the area where gas leakage or
buildup is expected, and can either be wall mounted or supported by electrical conduit carrying
interconnecting wiring.
Sensor/transmitters are available with optional Auto-Test, an
electrochemical gas generator which automatically tests sensor response daily and alarms any
sensor problems. For hazardous areas, explosion-proof sensor/transmitters are available.
A14 Receiver Module
Receives digital data from the sensor/transmitter and provides an LED display of gas
concentration, two gas alarm setpoints, three gas alarm relays, an isolated 4-20 mA output, and
a trouble alarm and relay. The receiver is packaged in a compact DIN rail mount housing, and
fits easily into NEMA 4X enclosures suitable for one, two, three, or six modules. Each module is
switch programmable for full scale range, alarm setpoints, relay latch/non-latch operation, and
relay normal/fail-safe operation. A single switch (marked A/R) on the front panel provides alarm
acknowledge and reset functions, and can also be used to test front panel LED indicators and to
inhibit alarm relays. LED bars on the front panel provide visual indication of alarm status.
A17 Power Supply Module
Provides 12 VDC power to one or two receiver modules plus power for an audible horn
and for charging an external battery. Packaged in the same compact DIN rail mount module
used for the receiver, the power supply is designed for use throughout the world. Input to this
module may be any AC (50 or 60 Hz.) or DC voltage between 85 and 270 volts. The supply is
self-regulating, meaning no jumper changes, no changes in switch settings, and no variation in
wiring pattern. A power failure alarm relay is included in the module to signal the loss of input
power.
NEMA 4X Enclosures
Four standard enclosures are available for housing receiver and power supply modules.
Polystyrene enclosures are suitable for outdoor environments, and digital displays and alarm
indicators are clearly visible through a clear polycarbonate window on the front. The window
hinges open to gain access to the receiver A/R control switch, and the entire front section of the
enclosure can be removed for ease of mounting and wiring. Enclosures are provided with
knockouts on all four sides to facilitate wiring, and 1/2" FNPT conduit hubs are provided with
each enclosure.
Explosion-proof Enclosures
Two versions are available to allow use of the receiver and power supply modules in
hazardous areas. One version is suitable for a single receiver module, while the second is large
enough to contain both a power supply and a receiver. Enclosures are rated for Class 1, Division
1, Groups C & D. Group B enclosures are also available if required. All explosion-proof
enclosures can be supplied with an external acknowledge and reset switch.
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GasSens Gas Detection System
Section 1 - Overview
Audible Horn
A 12 VDC piezoelectric alarm horn is available for mounting into any of the NEMA 4X
enclosures. The horn is wired to the receiver module and will sound intermittently when the
warning setpoint is reached, and continuously when the alarm setpoint is reached. The horn can
be silenced by pushing the A/R switch on the receiver front panel. A single horn can be wired
through multiple receivers and will sound if any receiver goes into alarm.
Strobe Lamp
Provides a bright visual indication of an alarm condition. The strobe uses a xenon flash
lamp to give a high intensity flash approximately 70 times a minute. The strobe is wired to one
of the alarm relays, with power for the strobe supplied from the power supply module. Mounting
is by 1/2" MNPT nipple, making it convenient to mount directly to a NEMA enclosure.
A19 Battery Back-up
Provides a 12 VDC, 4 AH battery and charging control circuitry in a separate NEMA 4X
enclosure. The battery backup connects directly to the A17 power supply module to provide
standby power to the detection system. If AC power is lost, the battery insures that detection
continues uninterrupted.
GasSens components allow simple assembly of either single or multipoint detection
systems. Each point of detection requires one sensor/transmitter and one receiver. The
sensor/transmitter is mounted in the hazard area, and the receiver is located anywhere within
1000 feet. If the user has a regulated 12 VDC power supply and an enclosure to house the
receiver, nothing else is required. If not, one power supply for every two receivers is needed for
power, and an enclosure of a size to contain the modules is needed for environmental protection.
An optional horn and strobe may be added if desired.
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GasSens Gas Detection System
Section 1 - Overview
MECHANICAL INSTALLATION
System enclosures, battery back-up units, and sensor transmitters are all designed for
surface mounting using screws or bolts inserted through the recessed mounting holes at each
corner of the enclosures. Included with each system enclosure is a template with mounting hole
dimensions for two and three module system enclosures, battery back-up enclosure, and
sensor/transmitter enclosure. The template can be used to mark hole centers on walls or
mounting panels.
Mounting recesses are suitable for #6 or #8 machine screws or wood screws. Screw length
will vary with specific site conditions.
Two and three module system enclosures provide knockouts on all four sides to allow wiring
conduit to be connected in the most convenient way. Enclosures are shipped with all knockouts
in place except for the larger knockout on the bottom, where the audible horn is installed if
ordered. See pages 1-6 through 1-9 for dimensional drawings of the one, two, three and six
module enclosures.
Each enclosure is supplied with conduit hubs for connection of 1/2" NPT threaded conduit.
Also included is a seal ring for each hub. Seal rings are required to provide a water tight
conduit hub connection to the enclosure. The following lists the number of hubs that should
be included with each enclosure type.
Two module Enclosure - 4 hubs
Three module Enclosure - 6 hubs
Six Module Enclosures - 6 hubs
Battery back-up Enclosure - 2 hubs
Sensor/Transmitter Enclosure - 1 hub
Conduit hubs are installed in any enclosure knockout labeled PG16. Note that some
knockouts have more than one designation, such as PG11/16. Those with two designations will
have concentric circles for knockouts. The inner circle marks the lower PG number while the
outer circle marks the higher number. Place a thin bladed screwdriver into the circular slot or the
desired knockout size and tap firmly with a hammer. To install the hub, place the seal ring over
the threaded part of the hub. Locate the hub nut on the inside of the enclosure and screw the
hub into the hub nut from the outside. Tighten firmly to insure that the seal ring provides a good
seal between the hub and the outside of the enclosure.
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GasSens Gas Detection System
Section 1 - Overview
For installations where conduit will not be used, cable gland seal fittings must be installed in
the conduit hubs. Plastic cable glands are available from most electrical supply stores. Gland
seals with 1/2" NPT threads will screw directly into the conduit hub. Gland seals are also
available from ATI for installation directly into the enclosures in place of the conduit hubs. Refer
to the parts list for the correct part number of the cable gland seals.
Figure 1-1: Single Module System Enclosure Dimensions (80-0005R)
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GasSens Gas Detection System
FRONT VIEW
Section 1 - Overview
SIDE VIEW
THRU HOLES FOR SURFACE
MOUNTING (4) #6 SCREWS
BOTTOM VIEW
Figure 1-2: Two Module System Enclosure Dimensions (80-0006R)
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GasSens Gas Detection System
FRONT VIEW
Section 1 - Overview
SIDE VIEW
THRU HOLES FOR SURFACE
MOUNTING (4) #6 SCREWS
BOTTOM VIEW
Figure 1-3: Three Module System Enclosure Dimensions (80-0007R)
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GasSens Gas Detection System
Section 1 - Overview
Figure 1-4: Six Module System Enclosure Dimensions (80-0008R)
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GasSens Gas Detection System
Section 1 - Overview
ELECTRICAL INSTALLATION
Field wiring required for a detection system includes connection of AC power, connection of
two conductor cable between the receiver and the sensor/transmitter, and connection of the
battery back-up unit if it was purchased with the system. ATI does not supply an AC power cord
with the system. A 25 foot length of 2 conductor interconnect cable is supplied for connection of
the sensor/transmitter to the receiver. Longer lengths up to 1000 feet may be used when
required.
Single point detection systems are supplied with the power supply, receiver, and optional
horn factory wired as shown in Figure 1-5 below.
Analytical Technology, Inc.
Figure 1-5: Single Point Receiver Internal Wiring (ATI-032)
Figure 2-2 in section 2 of this manual shows a detailed terminal wiring drawing for the
Receiver module. Figure 3-1 in section 3 shows a detailed terminal wiring drawing for the power
supply module.
A GasSens gas detection system will always contain an A14 Receiver and an A11 Sensor/
transmitter. Normally, an A17 Power Supply module will also be included, and an A19 Battery
Back-up Unit will often be used to provide standby power for the system. Figures 1-8 and 1-9
provide interconnect wiring diagrams for typical single channel systems.
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GasSens Gas Detection System
Section 1 - Overview
Two point detectors include one power supply and two receivers.
shipped factory wired as shown in Figure 1-6 below.
These systems are
Analytical Technology, Inc.
Figure 1-6: Dual Point Receiver Internal Wiring, (ATI-033)
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GasSens Gas Detection System
Section 1 - Overview
Analytical Technology, Inc.
Analytical Technology, Inc.
Figure 1-7: Four Point Receiver Internal Wiring (ATI-075)
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GasSens Gas Detection System
Section 1 - Overview
Multipoint systems supplied in “Large” type enclosures use a 65 watt power supply located in
the top of the enclosure. This power supply is designed to power up to 12 of the A14 receiver
modules. Figure 1-8 shows typical wiring for this type of system.
Figure 1-8: 65W Power Supply to A11 Wiring Diagram (ATI-0544)
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GasSens Gas Detection System
Section 1 - Overview
Sensor/transmitters contain two 2-position terminal blocks, one for receiver connection and one
for connection of the Auto-Test generator. Connection of the two wires from the receiver are not
polarity sensitive. These wires can be hooked up without regard to terminal position.
Connection of the generator is polarity sensitive. The generator will not function unless
connected properly. Sensor/transmitters supplied with the generator from the factory will be
factory wired. Adding a generator to an existing unit requires the installer to be sure that
generator wiring follows the diagram in Figure 1-8 below.
Analytical Technology, Inc.
Figure 1-9: Typical System Wiring, Nema-4 Transmitter Version (ATI-034)
CAUTION: Be very careful when removing the knockouts on the sensor/transmitter
enclosure. A small bladed screwdriver tapped firmly in the knockout recess
is all that is necessary. Do not drive the screwdriver blade into the
transmitter enclosure or it may strike the circuit board and cause component
damage.
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GasSens Gas Detection System
Section 1 - Overview
Analytical Technology, Inc.
Figure 1-10: Typical System Wiring, Explosion-proof Transmitter Version (ATI-076)
The remainder of this manual is divided into sections that describe each component of the
system. Mechanical and electrical installation are the only requirements to provide a workable
system. Power supply modules and battery back-up units require no adjustments. Receiver
modules are factory set to the range specified on the order, and alarm setpoints will be set to
default values unless otherwise specified on the order. Sensor/transmitters are factory
calibrated, and should require no adjustments when placed in service. Calibration can be
checked if desired according to the instructions in the Sensor/transmitter section of this manual.
Normal operation of the system is done using the switch on the Receiver module. The
"Operation" portion of the Receiver section (section 2) should be read and understood before
placing the detection system into operation.
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GasSens Gas Detection System
Section 2 - A14 Receiver Module
RECEIVER MODULE
Introduction
Series A14 Receivers provide the user interface to the gas detection system. Each receiver
is connected to a series A11 sensor/transmitter with a 2 conductor cable, and displays
information on the gas concentration in the sensor area. Receivers are powered by a separate
12 VDC power supply (part no. 00-0055) supplied as part of the system, or by a power supply
furnished by the user (12 VDC only).
4 DIGIT LED DISPLAY - INDICATES GAS
CONCENTRATION
GREEN LED - “POWER ON” BAR INDICATOR
WITH GAS SYMBOL DESIGNATION,
ENGINEERING UNITS (PPM, PPB, % OR % LEL)
AMBER & RED LEDS - “WARNING”
AND “ALARM” BAR INDICATORS
RED LED - “TROUBLE” BAR INDICATOR,
INDICATES LOSS OF TRANSMITTER INPUT
AND CERTAIN OTHER SYSTEM PROBLEMS
PUSHBUTTON FOR ALARM
ACKNOWLEDGMENT AND RESET
Figure 2-1: Front Panel Controls & LEDs (0109PM)
Receiver modules also include the following standard features:
1.
2.
3.
4.
5.
Three SPDT alarm relays, switch programmable for operating configuration.
One SPDT trouble relay, for remotely indicating that the TROUBLE alarm is activated.
Isolated 4-20 mA output signal proportional to gas concentration.
Isolated remote reset input terminals for remote alarm acknowledgment.
Power for operation of an A11 sensor/transmitter located up to 1000 feet away.
Receivers are housed in a compact noryl case designed for mounting to a 35 x 7.5 mm DIN
rail. The rails are supplied in standard ATI system enclosures, or can be supplied by a system
integrator as part of a custom panel arrangement. A spring clip on the back of the enclosure
holds the module to the rail. To remove from a rail, slide a thin bladed screwdriver through the
black loop at the top of the module and pull outward until the module releases from the rail. To
mount to the rail, reverse the procedure. When mounting, slide the bottom of the module
against the bottom of the rail before extending the spring clip.
Electrical Connection
Electrical connections to the receiver are made to two pluggable terminal blocks as shown in
Figure 2-2. Transmitter connections must be made at the time of installation, while power and
horn connections are factory wired when the receiver is part of a complete system. Connections
should be made and checked before power is applied to the module. Never connect or alter
connections while power is on.
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GasSens Gas Detection System
Section 2 - A14 Receiver Module
TB1
TB2
A1
TB1
1: +12 Module Power positive (12 VDC)
2: C Module Power Common
3: Earth Ground (REQUIRED)
4: H+ Audible Horn positive
5: H- Audible Horn negative
6: RR Remote Reset
7: RR Remote Reset
8: MA+ 4-20 mA output positive
9: MA- 4-20 ma output negative
10: Earth Ground
11: TR Transmitter Input
12: TR Transmitter Input
A2
A3
TROUBLE
TB2
1: A1 NO Alarm 1 normally open contact
2: A1 C Alarm 1 common
3: A1 NC Alarm 1 normally closed contact
4: A2 NO Alarm 2 normally open contact
5: A2 C Alarm 2 common
6: A2 NC Alarm 2 normally closed contact
7: A3 NO Alarm 3 normally open contact
8: A3 C Alarm 3 common
9: A3 NC Alarm 3 normally closed contact
10: TROUBLE NC trouble normally closed contact
11: TROUBLE C Trouble common
12: TROUBLE NO Trouble normally open contact
NOTE: Relay contact designation is shown for relays in normal mode of operation for relays A1,
A2 and A3. If fail-safe relay operation is selected, NO and NC designations are reversed
for that relay. The TROUBLE relay is set to fail-safe operation at the factory, and the
designation shown above is for the trouble relay in fail-safe mode.
Figure 2-2: Receiver Module Terminals (ATI-029)
CAUTION: Receiver modules MUST be connected to a secure earth ground. Terminal 3
of TB1 in Figure 2-2 above must be connected to the earth ground terminal of
ATI's power supply module as shown in the connection diagram in Figure 13. If the user is providing another 12 VDC supply, be sure that the receiver is
properly grounded.
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GasSens Gas Detection System
Section 2 - A14 Receiver Module
Factory Configuration
All receivers are identical except for the gas symbol attached to the green power LED.
Operating range, alarm relay configuration, display intensity, and Auto-Test activation are
selectable using 4 banks of DIP switches located on the configuration circuit board inside the
module.
Receivers are factory configured for the operating range specified on the customer order. If
the system is ordered with the Auto-Test option, this is also factory configured. Factory
configuration of the relays is as follows:
Relay 1 - Configured to trip at the Warning setpoint and set for normal, non-latching
operation.
Relay 2 - Configured to trip at the Alarm setpoint and set for normal, latching operation.
Relay 3 - Configured to trip at the Alarm setpoint and set for normal, latching operation.
Alarm Delay - Configured for 2 second delay.
Warning and Alarm setpoints are factory set to standard values depending on the operating
range. Except for oxygen systems, alarms are set to activate above the setpoints. Oxygen
alarms are set to activate below the setpoints.
The LED display will operate in either normal or high intensity mode. Normal mode is the
factory default setting, and is used when receivers are located indoors or in shaded areas. High
intensity mode is selected when receivers will be mounted outdoors. In high intensity mode, the
LED display can be read in direct sunlight.
Configuration Switches
Figure 2-3 indicates the location of each bank of DIP switches on the configuration P.C.
board and Figure 2-4 provides a description of the function of each switch on each bank.
BANK C
BANK A
BANK D
BANK B
Figure 2-3: Configuration Board Switch Location
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GasSens Gas Detection System
Section 2 - A14 Receiver Module
Figure 2-4: Configuration Switch Functions (0110PM)
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GasSens Gas Detection System
Section 2 - A14 Receiver Module
Setpoint Selection
The operating range and the Warning and Alarm setpoints can be changed, if desired, by
using the configuration switches identified in Figure 2-4. The Warning setpoint is set using
switches A2-A8 and the Alarm setpoint is set using switches B2-B8. A binary number is used to
select setpoints as a percent of operating range. For example, if you have a receiver range of 010 PPM and want to adjust a setpoint for 3 PPM, set the appropriate DIP switches to the binary
number for 30% from Table 2-1 below. Switches can be set using the tip of a ball point pen or
other tool with a small point on one end. Switch are two position, up indicating 'on' or a value of
'1' and down indicating 'off' or a value of '0'.
TABLE 2-1
%
SWITCH POS.
%
SWITCH POS.
%
SWITCH POS.
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
0000101
0000110
0000111
0001000
0001001
0001010
0001011
0001100
0001101
0001110
0001111
0010000
0010001
0010010
0010011
0010100
0010101
0010110
0010111
0011000
0011001
0011010
0011011
0011100
0011101
0011110
0011111
0100000
0100001
0100010
0100011
0100100
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
0100101
0100110
0100111
0101000
0101001
0101010
0101011
0101100
0101101
0101110
0101111
0110000
0110001
0110010
0110011
0110100
0110101
0110110
0110111
0111000
0111001
0111010
0111011
0111100
0111101
0111110
0111111
1000000
1000001
1000010
1000011
1000100
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
1000101
1000110
1000111
1001000
1001001
1001010
1001011
1001100
1001101
1001110
1001111
1010000
1010001
1010010
1010011
1010100
1010101
1010110
1010111
1011000
1011001
1011010
1011011
1011100
1011101
1011110
1011111
1100000
1100001
1100010
1100011
1100100
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GasSens Gas Detection System
Section 2 - A14 Receiver Module
Range Selection
Display range selection is made using binary numbers to represent the full scale operating
range for the receiver. Table 2-2 provides the proper switch settings for the ranges available on
each receiver. Range selection is made using switches C1-C4. The 4-20 mA output signal is
proportional to the selected range.
Ranges marked with 'LSD Fixed' indicate that the least significant digit on the display always
reads zero.
TABLE 2-2
DISPLAY
RANGE
SWITCH
SETTINGS
DISPLAY
RANGE
SWITCH
SETTINGS
0-1.00
0-2.00
0-3.00
0-4.0
0-5.0
0-10.0
0-20.0
0-25.0
0000
0001
0010
0011
0100
0101
0110
0111
0-50
0-100
0-200
0-500
0-1000
0-1000 LSD Fixed
0-2000 LSD Fixed
0-5000 LSD Fixed
1000
1001
1010
1011
1100
1101
1110
1111
Relay Configuration
Receivers contain 3 SPDT relays that actuate based on gas concentration. Relays can be
set to actuate when the gas concentration either goes above or falls below the setpoint. Most
gas leak detection applications require alarms to activate above a specific setpoint, but alarms
for oxygen deficiency require relay actuation below the setpoints. Switch A1 selects relay
operation either above or below setpoints and applies to all relays.
Each relay can be assigned to either the warning or alarm setpoint. As shown in Figure 2-4,
switches D3, D6, and C6 configure each relay . When warning is selected, the relay will activate
when the warning lamp on the front panel lights. When alarm is selected, the relay will activate
with the alarm lamp on the front panel.
Relays may be either Latching or Non-latching. A latching relay activates when gas
concentration exceeds the setpoint, but will only deactivate when the A/R button is pressed, and
then only if the gas concentration has fallen below the setpoint. A non-latching relay will
automatically deactivate when the gas concentration falls below the setpoint without A/R button
being pressed. Selection of the latch/non-latch function uses switches D4, D7, and C7.
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GasSens Gas Detection System
Section 2 - A14 Receiver Module
Relays may be configured for either Fail-safe or Normal operation. The designation of
normal or fail-safe refers to the operation of the relay coil during normal operation. A relay
configured for Normal operation will have the relay coil energized when an alarm occurs and deenergized during normal operation. A relay configured for Fail-safe operation has the relay coil
energized when conditions are normal and de-energizes when an event occurs. A fail-safe relay
will change state if power to the receiver is interrupted.
A short time delay precedes the activation of warning and alarm relays when a setpoint is
exceeded. This brief delay of 2 seconds eliminates false alarms due to transients that might be
encountered in a particular installation. The 2 second delay is the factory default and is selected
with switch B1. A 10 second delay may be selected if required in a specific application. The
delay time of either 2 or 10 seconds affects both the warning and alarm indicator lamps and the
associated relays.
External Horn Relay
Relay 3 provides an additional configuration option not available on relays 1 or 2. Switch C5
allows relay 3 to be configured for use in activating an external audible horn. When switch C5 is
on, relay 3 will operate in parallel with the internal horn. This means that any external horn tied
to that relay will sound intermittently when the warning setpoint is exceeded and will go to steady
on when the alarm setpoint is exceeded. The relay will deactivate when the A/R switch is
pressed, silencing the external horn.
Using relay 3 in the horn configuration eliminates the need for additional relay logic to
silence an external horn. This can provide significant cost savings in the installation of a
complete alarm system.
Display Intensity
The LED display on the receiver will operate in either normal or high intensity mode. The
factory setting is normal mode. Switch D2 is used to select high intensity mode for outdoor
installations.
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2-7
GasSens Gas Detection System
Section 2 - A14 Receiver Module
OPERATION
Startup
Receiver front panels contain four LED bar indicators and a 4 digit LED display. The digital
display indicates gas concentration in either PPM, PPB, or percent. The green LED bar is
marked with the gas symbol and units of measurement (PPM, PPB, or %) specified on the
customer order. LED bars also indicate WARNING, ALARM, and TROUBLE conditions.
12 VDC power for the receiver is supplied from the power supply module. When power is
first applied, the LED display will turn on and will step through three information displays. The
first number displayed is the full scale range. A 0-10 PPM unit will be indicated by "10.0" on the
display. After 3 seconds, the display will indicate the warning setpoint, the concentration at
which the warning relay will activate, with the WARNING lamp illuminated. After 3 seconds, the
display will indicate the alarm setpoint, with the ALARM lamp illuminated. At the end of this
sequence, the display will begin to indicate gas concentration. However, all alarm functions will
be inhibited for 5 minutes while the system is allowed to stabilize. This is indicated by
WARNING and ALARM lamps flashing in an alternating pattern. During this period, alarms will
not function, but the display will indicate the presence of any gas that might be in the area of the
sensor. Normally, the display will spike when power first comes on, and will slowly recover to
zero over the 5 minute period in which alarms are inhibited.
NOTE: Sensors may require up to 12 hours to stabilize after power up.
Alarm Acknowledge and Reset
The front panel of the receiver contains one button, marked A/R, which is used for a number
of different functions. When the receiver is in normal operation, a gas leak that exceeds the
warning setpoint will cause the WARNING indicator to flash and the internal horn to sound
intermittently. If the alarm setpoint is exceeded, the ALARM indicator will flash and the horn will
sound steadily. Pressing the A/R button the first time will silence the audible horn, and will
change the WARNING and ALARM indicators from flash to steady on. The indicator lamps will
remain lit until the gas condition has cleared. The WARNING indicator will automatically shut off
when gas concentration falls below the setpoint, but the ALARM indicator will remain lit.
Pressing the button after the alarm condition has cleared will reset the ALARM indicator.
Operation of the individual relays depends on the configuration selected for each one. As
shipped from the factory, relay 1 will energize when the WARNING indicator lights and will
automatically reset when the gas condition clears and the WARNING indicator shuts off. Relays
2 and 3 are configured to energize and latch when the ALARM indicator lights. These relays will
reset when the A/R button is pressed to reset the ALARM indicator. Changes in the relay
configuration switches will alter this operational sequence.
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2-8
GasSens Gas Detection System
Section 2 - A14 Receiver Module
Trouble Alarm and Relay
Receivers contain a TROUBLE indicator and an associated SPDT relay. The trouble alarm
will be activated if the transmitter cable is broken or shorted, or if electronic component failure in
either the transmitter or receiver causes a loss of digital input. If these conditions occur, the
TROUBLE indicator will light, the horn will sound intermittently, and the trouble relay will change
state. Note that the trouble relay is a fail-safe relay. Under normal conditions, the coil of this
relay is energized, and it de-energizes when a trouble alarm occurs. The trouble relay will also
change state if power fails.
For systems supplied with the Auto-Test option, the TROUBLE lamp will also indicate the
failure of a sensor to respond to the gas test that occurs automatically every 24 hours. Should
this type of failure occur, the TROUBLE indicator will flash, the trouble relay will change state,
and the audible horn will activate. Pressing the A/R switch will silence the horn, but the lamp
and relay cannot be reset for at least 10 minutes. The flashing TROUBLE light indicates that the
sensor and gas generator should be tested for proper operation using the manual Auto-Test. If
the sensor does not respond, the system should be tested using calibration or test gas as
described in the sensor/transmitter instructions. Pressing the A/R button resets the trouble relay
and indicator.
Auto-Test Function (Optional)
ATI's optional Auto-Test feature is a valuable tool for verifying the proper operation of a gas
detection system while saving manpower normally required for routine testing. Auto-Test is an
electrochemical gas generator fixed to the gas sensor and controlled from the receiver. Every
24 hours, the receiver automatically activates the gas generator and monitors the output of the
gas sensor. When the sensor responds normally, the generator is shut off and the system
returns to normal operation. With this feature in place, operation of every gas sensor is verified
daily. Manual testing is reduced to periodic calibration every 3-12 months, or when the receiver
indicates that a sensor has not passed its normal test.
While an Auto-Test is in progress, the alarm relays are inhibited. This is indicated by the
alternating flash pattern on the WARNING and ALARM indicators used during the 5 minute
power on delay. Typically, an Auto-Test will progress only a few minutes before the sensor
begins to respond. The actual time varies depending on the gas. A chlorine test normally takes
less than 30 seconds while a sulfur dioxide test can take as long as four minutes. Alarm relays
will remain inhibited for 10 minutes after completion of the test to allow the sensor to recover.
The alternating flash pattern will continue during this time.
During the first two minutes of the 10 minute inhibit period, alarms are completely inhibited.
The warning and alarm relays will not activate during this period. During the second 8 minute
period, the alarms are only partially inhibited. The inhibit flash pattern will continue during the 8
minute period, but the inhibit will be superseded by an alarm should the measured gas
concentration exceed 50% of range. This means that alarm protection is partially restored to
protect against any major leak during this period. At the end of the 10 minute inhibit period, the
alternating flash will end and the unit will return to normal operation.
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GasSens Gas Detection System
Section 2 - A14 Receiver Module
When the Auto-Test is activated, the generator will turn on for a maximum of 5 minutes. If no
sensor response is detected during this time, the generator will turn off and the receiver will wait
for 15 minutes before initiating another Auto-Test. If no sensor response is detected after the
second test, the trouble indicator will flash, trouble relay will change state, and the horn will
sound. The test sequence will be repeated twice more at one hour intervals. If the system
passes, alarms will automatically shut off. If it fails, the alarms will continue to be energized. If
the trouble alarm has been manually acknowledged and reset between tests, a failure will
reactivate the trouble alarm.
NOTE: No Auto-Test will be initiated if the measured gas concentration is above either of
the two setpoints. If this condition exists, the receiver will wait for another 24
hours before initiating another Auto-Test sequence.
Lamp and Horn Test
Verification that all digital display segments and alarm indicator bars are functional is done
using the A/R button to initiate a lamp test. If the detection system includes an internal horn, the
horn is also tested as part of the lamp test.
To activate the lamp test, press and hold the A/R button for 2 seconds and all front panel
indicators will light. The horn will also sound briefly. Immediately release the button and the
indicators will return to normal. During this test, alarm relays will not be activated.
Relay Inhibit
Alarm relays in the receiver can be inhibited for up to 4 hours to allow calibration or testing of
sensor/transmitters without activating external alarm or control devices. Inhibit is activated
through the use of the A/R button.
Press and hold the button for approximately 5 seconds. The lamp test will occur first, but
continue to hold the button down. Once the lamps have shut off, release the button. The
WARNING and ALARM lamps will begin an alternating flash pattern, and, if the receiver is
configured for Auto-Test, the flash will switch to the trouble lamp. If you do nothing, the flash will
switch between the WARNING/ALARM lamps and TROUBLE lamp twice and then revert to
normal operation.
If the A/R button is pressed and released while the WARNING and ALARM lamps are in
alternating flash, the receiver will go into the relay inhibit mode (if a horn is connected, a quick
beep will sound when the inhibit is selected). The WARNING and ALARM lamps will continue
their alternating flash for 4 hours or until the A/R button is pressed again. During this period, the
display will indicate gas concentration, but the relays will not. Transmitters may be calibrated
while the inhibit is on without activating external alarms.
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2 - 10
GasSens Gas Detection System
Section 2 - A14 Receiver Module
Manual Auto-Test
Gas detection systems purchased with the optional Auto-Test generator may be tested by
manual activation of the generator from the receiver module. This function will operate only if
the Auto-Test configuration switch D1 is 'on'. As with the lamp test and alarm inhibit, access to
manual operation of the generator is through the A/R button.
Press and hold the button for approximately 5 seconds. The lamp test will occur first but
continue to hold the button down. When the lamps have shut off, release the button. The
number of hours since the last successful auto-test (automatic or manual) will appear on the
display. When the WARNING/ALARM flash is alternating with the TROUBLE flash, you can
select manual activation of the generator rather than relay inhibit. Press the A/R button when
the TROUBLE lamp is flashing (if a horn is connected, a quick beep will sound when the AutoTest is selected). The green gas indicator will begin to flash, indicating that the generator is
activated. The system will go through a normal Auto-Test sequence, exactly the same as the
sequence used every 24 hours. If you observe the display, you will see increasing gas values as
the sensor begins to respond. Upon completion of a successful test, the horn will sound a single
beep. The inhibit will remain on for an additional 10 minutes while the sensor recovers to zero.
Should the test be unsuccessful, the TROUBLE lamp will light and the alarm relay and horn will
activate. Pressing the A/R button will silence the horn, but the alarm cannot be reset for at least
10 minutes after a failure of the manually activated Auto-Test. This period will allow time to
manually inspect the sensor to determine the reason for the failure
If the manual Auto-Test sequence results in a trouble alarm, check the sensor/transmitter.
Either the sensor or generator has failed, or the diffusion path between the two is physically
blocked. Methods for testing individual gas sensors can be found in specific sensor/transmitter
instructions.
Remote Reset
Receivers are provided with input terminals for connection of a remote reset switch. The
remote reset input provides horn silence and alarm reset functions using a switch located at a
remote point. When receivers are located at sites with telemetry equipment, the remote reset
input may be connected to a relay contact in the telemetry system.
The remote reset input accomplishes the same acknowledge and reset functions as the A/R
button on the front panel. When a switch closure is detected across the remote reset terminals,
the detector horn will silence and any latching relays will reset, provided that the gas condition
has cleared. The remote reset input will not activate any of the testing or inhibit functions of the
receiver.
Analog Output
Receivers provide an isolated 4-20 mA output signal for interface with recorders, data
loggers, or computer systems. The span of the 4-20 mA signal is the same as the range of the
receiver selected during the receiver configuration. The output will drive loads up to 1200 ohms.
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2 - 11
GasSens Gas Detection System
Section 2 - A14 Receiver Module
Auto-Test Remote Verification
A14 Receiver modules with a software revision G or higher use the analog output to indicate
that a successful Auto-Test has occurred. This allows a recording device to show evidence of
the successful test. During an Auto-Test, the 4-20 mA output is locked at 4 mA while the test is
in process. If the test is successful, the output will go up by 3% (to 4.48 mA) and will remain at
that value until the 10 minute inhibit period is complete, after which it will return to 4 mA.
Deactivating the Auto-Test Function
A14 Receiver modules with software revision G or higher have the capability of temporarily
deactivating the Auto-Test function without having to open the module and change the DIP
switch that controls this function. This might be necessary if an Auto-Test failure has been
traced to a failure of the generator. If proper sensor operation has been verified, the automatic
daily activation of the test function can be bypassed until a replacement generator has been
installed.
To deactivate the Auto-Test, press and hold the A/R button for a full 15 seconds. As you
hold the button, the lamps will turn on and then shut off again. Finally, the green power LED will
shut off so that there will be no lamps lit at all. Release the A/R button. After this is done, you
will see the green LED periodically flash quickly. This is simply a visual reminder that the AutoTest has been temporarily deactivated.
To return the receiver to normal operation, press and hold the A/R button until all the lamps
and display segments light up. Then let go of the switch and the unit will return to normal
operation. Alternately, simply turn the power off and then back on. This will also override the
temporary inhibit.
NOTE: If power goes off while the Auto-Test is temporarily deactivated, it will come back on in
normal mode. You must again deactivate the Auto-Test again or it will attempt the test
24 hours later.
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2 - 12
GasSens Gas Detection System
Section 2 - A14 Receiver Module
TROUBLESHOOTING
Receiver modules will normally provide trouble free operation over many years of service.
However, should problems arise, a few simple tests can be done to determine if the receiver is
functioning properly.
LED display and green gas indicator do not light when power is applied to the system.
1. Check polarity of the power connection at terminals 1 and 2 of TB1. Terminal 1 must be
positive and terminal 2 must be negative.
2. With a voltmeter, check the power supply at terminals 1 and 2 of TB1. Input power supply
must be 11 to 15 VDC.
Receiver module powers up correctly, but does not respond when test gas is applied to
sensor/transmitter.
1. Disconnect transmitter connections at terminals 11 and 12 of TB1. Check the voltage on the
terminals with a voltmeter. The voltage should be about 12 VDC.
2. Connect a milliamp meter between terminal 11 and 12 of TB1. The current should measure
about 20 mA.
Problems in the receiver module can only be caused by an electronic component failure. In
most cases, the simplest solution is to remove the module and install a replacement.
Troubleshooting the electronic circuit boards is best handled by trained technician familiar with
the circuits. As modules are small and easily shipped, it is best to return defective modules to
ATI for service.
Modules failing during the warranty period will be exchanged by ATI with replacement units.
Contact the ATI service department for assistance.
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2 - 13
GasSens Gas Detection System
Section 2 - A14 Receiver Module
RECEIVER MODULE PARTS LIST
TOP HALF OF ENCLOSURE (80-0002)
PLUG-ON TERMINAL BLOCK (38-0006)
BOTTOM HALF OF ENCLOSURE (80-0002)
PC BOARD ASSEMLBY
FRONT PANEL (34-0009)
PLUG-ON TERMINAL BLOCK (38-0009)
Part Number
Description
00-0056
80-0002
34-0009
38-0009
38-0006
Complete receiver module (Specify Gas)
Module enclosure (top and bottom)
Front panel
Relay terminal block plug, 12 position
DC terminal block plug, 12 position
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2 - 14
Universal Power Supply
Section 3 – A17 Power Supply Module
A17 UNIVERSAL POWER SUPPLY
The power supply module used in the GasSens system (part #00-0055) is a self-adjusting supply
that will accept the AC power provided in virtually every country in the world. Any AC (50-60 Hz.) or DC
voltage from 85 volts to 270 volts can be connected to the power input terminals on TB4. There are no
adjustments of any kind required.
The output of the power supply is a regulated 13.7 VDC. There are 3 sets of DC terminals at the top
of the module for connection to receivers and external battery back-up unit. This voltage permits float
charging of a an optional separate 12 volt lead acid battery for detector system back-up.
Power supply modules are rated for 1 ampere output, and will deliver higher current for periods.
Each optional receiver module draws a maximum of 300 mA, and will normally draw about 125 mA. The
optional external battery back-up unit can draw up to 750 mA for a few hours if the battery is deeply
discharged, which will drop sharply as the battery approaches full charge. The audible horn draws less
than 10 mA average current, and an optional strobe will draw approximately 400 mA when activated.
The power supply is internally fused at 2 Amps. The fuse is not user replaceable. (Note: Only
Qualified Service Personnel will replace the fuse, using the same type and rating as indicated on the
fuse.)
The power supply has a power-on indicator LED and provides a SPDT relay to indicate power failure.
The relay coil is energized by power from the input power terminals and will de-energize if power is lost.
This relay is convenient for input to telemetry systems to indicate loss of power at a remote site.
Mounting of power supply modules is done by clipping them to a standard 35 x 7.5 mm DIN rail. A
spring loaded clip holds the module to the rail and is used for mounting and removal. From the front, the
clip is seen as a black loop at the top rear of the module. To remove from a rail, place a small
screwdriver into the opening in the black loop and pull outward until the module releases from the rail.
Reverse the procedure to mount the module.
CAUTION
The power supply module is sealed, and the seal should not be broken. Never attempt to
disassemble or service the power supply module. Service on this module should only be done
only by a qualified service technician familiar with the circuit design and equipped with the
proper service equipment.
Severe electrical shock may result from touching internal
components with input power applied.
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3- 1
Universal Power Supply
Section 3 – A17 Power Supply Module
Figure 3-1 provides detailed information on the terminals provided on the power supply. All terminal
blocks are plug-in type, and can be easily unplugged should removal of the module be necessary.
Analytical Technology, Inc.
TB1
(12V Battery only)
1: +12 External Battery (+)
2: C External Battery (-)
3: Earth Ground
TB2
1: +12 Receiver Module (+)
2: C Receiver Module
Common
3: Earth Ground
TB4
1: L AC power hot (85-255 VAC)
2: N AC power neutral
3: AC power ground (earth ground REQUIRED)
TB3
1: +12 Receiver Module (+)
2: C Receiver Module Common
3: Earth Ground
TB5
1: NC Power failure normally closed contact
2: C Power failure common
3: NO Power failure normally open contact
NOTE: AC power input must be properly earth grounded for safe operation. 220 VAC power without a
neutral line may not be used with this power supply.
Figure 3-1: Power Supply Terminal Connections (ATI-030)
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A14-RK, 8/06
3- 2
Universal Power Supply
Section 3 – A17 Power Supply Module
POWER SUPPLY PARTS LIST
Part Number
Description
00-0055
81-0064
34-0011
38-0065
38-0066
Complete power supply module
Module enclosure (top and bottom)
Front overlay
AC power terminal block plug, 3 position
Power failure relay & DC terminal block plug, 3 position
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3- 3
GasSens Gas Detection System
Section 4 - Optional Equipment
OPTIONAL EQUIPMENT
Battery back-up units for GasSens detection systems (part #00-0057) are separate components
housed in a NEMA 4X wall mount enclosure. Back-up units include a 4 ampere-hour sealed lead acid
battery with a control circuit attached to the battery terminals. The battery is held in place on an
aluminum bracket fixed to the plastic enclosure.
Installation
Figure 4-1 shows the dimensions of the battery back-up unit and the mounting hole centers. Two
conduit hubs are supplied with the unit, one for use on the battery back-up enclosure and one for use on
the receiver enclosure. When mounting the battery back-up unit, be careful to hold the module
securely when screwing the enclosure in place. The battery is heavy and could cause injury to
feet if it should fall directly on them. The battery and attached circuit board are held in place with a
wire tie. Should you wish to remove the battery, the wire tie must be cut. When replacing the battery,
secure with a new wire tie. Replacement batteries from ATI are supplied with the proper wire tie.
Figure 4-1: Battery Backup Enclosure Dimensions (80-0008)
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4-1
GasSens Gas Detection System
Section 4 - Optional Equipment
Electrical connection is made between the battery back-up unit and the power supply module. The
circuit board mounted on the battery contains a 2 position plug-in terminal block marked plus and minus.
The plus terminal is connected to terminal B+ of the power supply and the minus terminal is connected to
B- of the power supply.
Operation
When power is applied to the power supply module, a relay on the battery back-up circuit board
energizes and places the battery back-up into operation. There are no user adjustments in the battery
back-up unit. If the battery is not fully charged, the power supply will begin supplying charge current to
the battery, and will float charge the battery as long as the power supply is on.
Should the power supply loose its input power, the battery back-up will immediately supply power to
receiver modules to maintain detection system operation without interruption. The back-up period will
vary depending on whether the detector is single channel or two channel, on whether displays are in
normal or high intensity mode, and on how many relays are configured for fail-safe operation. The
minimum period expected for a single channel system is 12 hours and for a two channel system is 6
hours. Normally, the back-up period is twice as long as the minimums.
The circuit board attached to the battery serves two functions. First, it regulates the charging current
to the battery to a maximum of 0.75 amps. This prevents possible damage to the battery due to an
excessively high charge current. Second, it isolates the battery from the detection system when the
battery voltage falls below 10 volts. This is done through a relay, and protects the battery against
damage caused by very deep discharge.
The isolation relay that protects against deep discharge will also protect the battery against an
external short circuit of the wires connected to the battery. If a short occurs, the relay will immediately
open, protecting the battery and limiting the current that the battery will deliver.
Removal from Service
The relay that isolates the battery when the 10 volt level is reached is energized as soon as power is
applied to the power supply module. Once energized, the coil current is supplied from the battery if
needed. If the gas detection system supported by the battery back-up is started up for testing and then
shut down, the battery back-up relay should be de-energized manually. Otherwise, the relay coil will
continue to draw power from the battery until the 10 volt level is reached. While this will not cause
damage, it means that the battery will be discharged when the detection system is started up again.
To de-energize the relay, slide the control circuit board off the battery terminals briefly and then slide
it back on. As soon as the battery connection is broken, the relay coil will drop out, and will not energize
until power is applied to the power supply module in the system. This procedure is recommended any
time the detection system is to be shut down for more that a few days.
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4-2
GasSens Gas Detection System
Section 4 - Optional Equipment
BATTERY BACKUP PARTS LIST
Part Number
Description
00-0057
01-0011
80-0009
48-0010
29-0002
92-0022
44-0017
44-0018
Complete battery back-up unit
Battery back-up circuit board
NEMA 4X enclosure (top and bottom)
Battery bracket
Battery, 12 V, 4 A-H
Self-tapping screws, (Pkg. Of 2)
Pg 16 to 1/2" NPT conduit hub
Pg 16 Seal Ring (required for NEMA-4X rating on hub)
STROBE PARTS LIST
Part Number
Description
35-0002
35-0005
35-0004
35-0006
Red Strobe, 12-80 VDC
Red Strobe, 120 VAC
Amber Strobe, 12-48 VDC
Amber Strobe, 120 VAC
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4-3
GasSens Gas Detection System
Section 4 - Optional Equipment
STROBE LIGHT
The accessory alarm indicating strobe light (part number 35-0002) available for use with the
GasSens alarm system is a weatherproof high-intensity strobe operating from a 12 VDC power source.
The strobe can be conveniently mounted on the top or either side of the alarm enclosure using one of the
1/2" NPT hubs supplied with the unit. The bottom of the strobe also contains a 1/2" NPT mounting
adapter, so that only a 1/2" pipe nipple is needed to complete the assembly. The necessary nipple is
available from most hardware stores or plumbing supply outlets.
For remote applications, the strobe should be mounted to 1/2" conduit, with a junction box nearby for
splicing the strobe wires to the interconnect wiring running to the alarm unit. This wiring should be kept
separate from AC power wiring to avoid accidental connection of AC power to the strobe, which will
damage the lamp.
The 12 VDC power to operate the strobe can be picked up from the power supply module which is
part of the alarm unit. Figure 4-2 shows the typical wiring diagram for connection of the strobe. The
wiring diagram shows the plus side of the 12 VDC supply brought to the common of the alarm contact,
one side of the strobe wired to the normally open (NO) contact, and the other side of the strobe
connected to the minus side of the 12 VDC supply. Connection of the strobe lamp directly across the
alarm relay will not operate the strobe because alarm contacts are unpowered.
CAUTION: Strobe light connection is polarity sensitive. Check wiring to be sure that the +12 is
connected to the red strobe wire.
Analytical Technology, Inc.
Figure 4-2: External Strobe Light Connections (ATI-0240)
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Section 5 - A11-24 H2S Sensor/Transmitter
INTRODUCTION
Series A11 sensor/transmitters combine electrochemical gas sensors and an electronic amplifier
that transmits gas concentration using a current pulse position technique. When ordered as an option,
sensor/transmitters are also supplied with the gas generator that provides the Auto-Test automatic sensor
testing system.
Gas sensors are housed in a corrosion resistant plastic housing connected to the transmitter
enclosure through a knockout. A short sensor cable with three pin socket connects the sensor to the
transmitter circuit board. The optional gas generator connects to a 2 position terminal block on the circuit
board. For hazardous area applications, sensor/transmitters are housed in a cast aluminum explosionproof enclosure and the sensor is contained in a stainless steel shell with explosion-proof cable seal.
Auto-Test generators are not available on explosion-proof sensor/transmitters.
Sensor/transmitters are powered from a current limited 12 volt supply provided by the receiver.
Do not attempt to operate the transmitter from another 12 volt power supply or the transmitter will
be damaged. If you wish to perform a calibration on the bench, use a spare receiver module to power the
transmitter. A separate 12 volt supply can be used if the current is limited to a maximum of 20 mA.
INSTALLATION
Sensor/transmitters are surface mounted using screws or bolts as required. Figure 5-1 & 5-2
provides the dimensions for both the standard and explosion-proof transmitters. Standard enclosures will
accommodate #6 or #8 screws which are not supplied. For standard transmitters not equipped with AutoTest, the sensor may be oriented either horizontally as shown in Figure 5-1 or facing downward.
Sensor/transmitters supplied with the Auto-Test generator must be mounted with the sensor
horizontal. For pipe mounting, special 2" pipe mounting brackets are available
Explosion-proof transmitters mount with 1/4-20 bolts to any vertical surface. The sensor
orientation may be either horizontal or facing downward, as shown in Figure 5-2. To maintain the
explosion-proof integrity of the transmitter, a suitable cable entry seal must be used in accordance with the
applicable electrical code.
NOTE: Gas sensors not equipped with Auto-Test generators are shipped with a protective plastic
cap over the end. This cap should be left in place to avoid damage to the sensor during
installation. If the detection system is to be activated within a few days of installation, the
cap should be removed when installation is complete. Otherwise, leave the cap in place
until the system is to be placed in service. Be sure to leave the protective cap on the sensor
if painting is to be done in the area of the sensor.
Installation wiring requires connection of a 2 conductor cable from the receiver. Connection is
made at the terminals marked TB1 on Figure 5-4. This connection is not polarity sensitive so you can
connect either conductor to either terminal. The cable supplied with the system is unshielded #20 gauge
stranded.
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Section 5 - A11-24 H2S Sensor/Transmitter
Notes:
1) Enclosure Ratings: Nema-4X/IP 66.
2) Enclosure Material: Polystyrene, standard gray
3) Knockouts: Pg 11 (.75” dia.)
Pg 16 (.90” dia.)
4) **These are the dimensions between knockouts and
are typical for (3) sides with (2) knockouts each.
Figure 5-1: Nema-4X Sensor/Transmitter Dimensions (ATI-017, ATI-0169)
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Section 5 - A11-24 H2S Sensor/Transmitter
Figure 5-2: Explosion-Proof Sensor/Transmitter Dimensions (ATI-046, ATI-0170)
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Section 5 - A11-24 H2S Sensor/Transmitter
SENSOR LOCATION
Hydrogen sulfide gas is slightly heavier than air and will tend to accumulate near the floor in a
closed room with little air movement. If there is good air circulation in an enclosed area, H2S will mix
fairly well throughout the area. Hydrogen sulfide sensors should be located one to two feet off the floor in
closed storage rooms, but may be located at higher elevations in outdoor areas or where good air flow will
quickly mix any leaking gas throughout the space. Outdoor sensor locations require that prevailing wind
patterns, likely personnel work areas, and most probable leak sources all be evaluated to determine where
sensors will detect leakage with the shortest response time.
INTERFERENCES
The A11-24 sensor/transmitter uses an electrochemical sensor manufactured by ATI. It is
designed to measure H2S gas concentration in air with a maximum of sensitivity and a minimum of
interference from other gases.
Unfortunately, electrochemical sensors are not 100% selective and do exhibit response to other
gases that may be present in ambient air. Table 5-3 lists the possible interferences that may be
encountered when using the Hydrogen Sulfide Detector. The table indicates the relative response of the
H2S sensor to 1 PPM of the listed gas, expressed in terms of relative PPM H2S signal. For example,
exposure of a hydrogen sulfide sensor to a gas sample containing 1 PPM of SO2 would produce a signal
equivalent to 0.1 PPM of hydrogen sulfide. A negative sign (-) indicates an interference that could cause
low H2S measurements if a mixture of H2S and that gas were encountered.
TABLE 5-3
INTERFERENCE
HYDRIDES
METHYL MERCAPTAN
SULFUR DIOXIDE
NITRIC OXIDE
ACETYLENE
ETHANOL
NITROGEN DIOXIDE
HYDROGEN
RESPONSE
0.5
0.3
0.1
0.1
0.01
0.05
0.05
0.005
CALIBRATION
Hydrogen sulfide sensor/transmitters are factory calibrated for the operating range specified on
the order, with the calibrated range shown on the calibration tag attached inside the lid of the transmitter
enclosure. For critical applications, sensor/transmitters should be calibrated every 3-6 months. When
used primarily for high level leak detection, yearly calibration is probably sufficient. Keep in mind that
the best calibration sources are generally ±10% accurate, and that a sensor/transmitter will normally
change sensitivity by less than 25% over 12 months time.
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Section 5 - A11-24 H2S Sensor/Transmitter
Calibration of an H2S sensor/transmitter requires a digital volt meter (DVM), a source of
calibration gas, and a calibration adapter for the sensor. Calibration gas can be obtained in convenient
disposable cylinders from specialty gas suppliers such as Scott Specialty Gases, Alphagaz, or Matheson
Gas Products. Complete calibration kits may also be purchased from ATI (part no. 00-0180). These kits
contain one 25 PPM H2S gas standard in a disposable cylinder, a bottle of zero air, and a cylinder
regulator. A calibration adapter must be purchased separately. Gas standards of about 25 PPM are
recommended for standard 0-50 PPM transmitters. For higher ranges, standards of about 50% of range
are recommended.
NOTE: If using the receiver display when adjusting the transmitter zero, place the receiver in the
"Inhibit" mode as described in Section 2 of the manual. When in the inhibit mode, the
blanking around zero is disabled so that the zero can be set accurately.
If a sensor/transmitter is equipped with a generator, the generator must be removed prior to
calibration. The generator will unscrew from the sensor. It is not necessary to disconnect the generator
electrical connection from the transmitter circuit board. Once the generator is removed, the calibration
adapter can be attached to the sensor. The calibration adapter slides on to the end of the sensor, and is
connected to the gas source using flexible tubing.
Prior to calibration, remove the cover from the sensor/transmitter enclosure and connect a DVM
to the test points shown in Figure 5-4. The same octagonal transmitter circuit board shown in Figure 5-4
will be found in the explosion-proof transmitter. The test points will provide a 0-1.00 VDC signal
proportional to transmitter range. For a standard 0-50 PPM unit, 0 PPM is 0.00 volts and 50 PPM is 1.00
volts.
FIGURE 5-4: SENSOR/TRANSMITTER CONTROLS AND TEST POINTS (ATI-096)
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Section 5 - A11-24 H2S Sensor/Transmitter
TRANSMITTER ZERO
The transmitter zero is adjusted with the sensor exposed to air that contains no hydrogen sulfide.
Generally, the easiest method of zeroing the transmitter is to make the adjustment when you know that the
area is free of H2S gas. The absence of hydrogen sulfide can be verified fairly easily by isolating the
sensor from the ambient air and observing the test point voltage (or the receiver display, if nearby). Prior
to placing the calibration adapter on the sensor, observe the DVM reading. Slide the calibration adapter
onto the end of the sensor and observe the DVM reading for the next 5 minutes. If H2S or some
interfering gas is present in the ambient air, the value on the DVM will begin to decline. If the value
remains stable (± 0.02), the sensor is at zero, and the DVM reading can be adjusted to 0.00 ± 0.01 VDC
using the zero potentiometer shown in Figure 5-4.
The transmitter can also be set to zero using "zero air" available in cylinders. Zero air cylinders
and regulators are available from ATI or from specialty gas suppliers. Connect the zero air cylinder to the
calibration adapter and adjust gas flow to 500 cc/min. When the display stabilizes near zero, adjust the
zero potentiometer until the display reads 0.00 ± 0.01 VDC.
NOTE: If using the receiver display when adjusting the transmitter zero, place the receiver in the
"Inhibit" mode as described in Section 2 of the manual. When in the inhibit mode, the
blanking around zero is disabled so that the zero can be set accurately.
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Section 5 - A11-24 H2S Sensor/Transmitter
TRANSMITTER SPAN
To span the sensor/transmitter, connect tubing from your span gas cylinder to the calibration
adapter inlet. Turn on the gas flow and adjust to approximately 500 cc/min. (ATI calibration kits contain
fixed flow regulators that automatically provide 500 cc/min. flow). The reading on the DVM attached to
the transmitter test points will immediately start to increase. Allow the gas to flow to the sensor for 5
minutes and observe the reading on the DVM. The reading should be relatively stable ± 0.05 VDC. Use
the span potentiometer to adjust the DVM to the voltage equivalent to the value of the span gas. The
voltage you set will be dependent on the hydrogen sulfide concentration used to span the transmitter. The
proper voltage is calculated as follows:
V = 1.00 X (Span Gas Concentration ÷ Transmitter Range)
As an example, if your span gas cylinder is marked with a concentration of 25 PPM H2S and it is
used to calibrate a 0-50 PPM sensor transmitter, the calculation would be:
V = 1.00 X (25 ÷ 50) = 0.50 VDC
When the span has been set, turn off the span gas flow and remove the calibration adapter from
the sensor. Replace the Auto-Test generator if in use. Place the lid back on the transmitter enclosure and
tighten the screws to insure the enclosure remains water tight. If the receiver is nearby and the alarm
relays were inhibited prior to calibration, press the A/R switch to return the system to normal operation.
SENSOR RESPONSE TEST
While zero and span adjustments are required only periodically, gas sensors should be checked
regularly for proper response. For systems not equipped with Auto-Test, manual sensor response testing
once a week is recommended. The response test can be done using the calibration gas cylinder used for
calibration.
The sensor response test will create a condition where alarm relays will be activated unless they
are inhibited as described in the receiver section. To observe the response at the transmitter, it is
necessary to connect a DVM to the test points indicated in Figure 5-4. If the receiver is nearby, you may
simply observe the digital display on the receiver.
Open the regulator valve on the calibration gas cylinder and aim the outlet tubing directly at the
face of the sensor. The sensor should respond fairly quickly upscale as indicated by an increase in the test
point voltage or an increase in the reading on the digital display of the receiver. You should only need to
run gas on the sensor for 10-20 seconds in order to verify that the sensor is still responding properly.
The sensor response test described above should also be used if the Auto-Test systems detects a
sensing failure and lights the Trouble lamp. If this occurs, remove the generator and test the H2S sensor
as described above. If the sensor does not respond, sensor replacement is required. If the sensor responds
to the H2S coming from the bottle, activate the generator manually to see if hydrogen sulfide is being
generated. If the sensor does not respond, replace the generator.
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Section 5 - A11-24 H2S Sensor/Transmitter
SENSOR REPLACEMENT
Electrochemical sensors used in the A11 are warranted for 12 months and generally last 18-24
months. When sensor replacement is required, it can be done easily and quickly. Open the transmitter
and unplug the sensor cable from the transmitter circuit board. Unscrew the sensor from the nut on the
inside of the enclosure and screw in the replacement sensor. For explosion-proof transmitters, there is no
nut, since the stainless steel sensor housing threads directly into the enclosure.
Connect the new sensor to the pins on the transmitter board and replace the transmitter cover.
After a new sensor has been connected, allow 12 hours for the new sensor to completely stabilize. Then
perform a zero and span as described on pages 4 and 5.
GENERATOR REPLACEMENT
Auto-Test gas generators are warranted for 12 months and will generally last for 24 months or
more. To replace, disconnect the generator leads from the terminal block marked TB2 on Figure 5-4.
Loosen the cable gland, pull the wires out of the enclosure, and unscrew the generator from the sensor.
Reverse the process to install the new generator. Observe the wiring polarity when installing the new
generator.
Once installed, the new generator should be tested by running the Manual Auto-Test procedure
described in the Receiver section. If no sensor response is observed, recheck the generator connection to
be sure the polarity is correct. If the sensor still does not respond, test the sensor with the Sensor
Response Test described on page 4. If the sensor does not respond, replace it. If the sensor responds
properly, contact ATI for assistance with the generator.
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Section 5 - A11-24 H2S Sensor/Transmitter
H2S SENSOR/TRANSMITTER PARTS LIST
Part Number
Description
00-0117
00-0091
00-0109
00-0138
01-0030
80-0012
38-0002
92-0005
44-0017
44-0018
Complete hydrogen sulfide sensor/transmitter assembly (including sensor)
Hydrogen sulfide gas sensor, Std.
Hydrogen sulfide gas sensor, explosion-proof
Hydrogen sulfide gas generator with gland seal
Transmitter circuit board
NEMA 4X enclosure (top and bottom)
Terminal block plug, 2 position
Self-tapping screw (#8 x 1/2")
1/2" NPT conduit hub
Seal ring (required for NEMA 4X rating on fittings)
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