ATI Technologies D12-17 User manual

-0992 Fax: + 44 (0)1457-874-468
O & M Manual
D12-17
% LEL Gas Transmiter
Home Office European Office
Analytical Technology, Inc. ATI (UK) Limited
6 Iron Bridge Drive Unit 1 & 2 Gatehead Business Park
Collegeville, PA 19426 Delph New Road, Delph
Phone: [phone] Saddleworth OL3 5DE
610-917-0991 Phone: [phone]
Fax: [phone] Fax: + 44 (0)1457-874-468
Email: [email protected] Email: [email protected]
Web: www.Analyticaltechnology.com

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
4
Table Of Contents
INTRODUCTION _______________________5
COMPONENTS..........................................................5
D12 LEL Transmitter........................................................5
The Combustible Gas Sensor..........................................5
Active Element..................................................................5
Reference Element............................................................5
Auto-test Option................................................................5
Gas Mixtures.....................................................................6
LEL, UEL...........................................................................6
%LEL................................................................................6
OTM Gases (Other Than Methane)...................................6
Multiple Gas Safety...........................................................7
Oxygen is Essential...........................................................7
Gas Flooding.....................................................................7
Compounds to Avoid.........................................................7
SPECIFICATIONS______________________8
INSTALLATION________________________9
MECHANICAL MOUNTING.......................................9
Transmitter.......................................................................9
ELECTRICAL CONNECTIONS.................................11
The Stack.........................................................................11
External Power Supply.....................................................11
Power Supply Board ........................................................12
Relay Contacts..................................................................13
Wiring Examples..............................................................14
ATI A17/B14, 3-Wire Mode................................................14
Power Without 4-20mA Signaling......................................15
4-20mA Signaling, Single Supply, 3-Wire Mode ................16
4-20mA Signaling, Dual Supply, 4-Wire Mode...................17
HART Transmitter, Point-to-Point, 3-Wire (Active Source).18
HART Transmitter, Multi-drop, 3-Wire (Active Source).......19
RS485 Modbus Multidrop..................................................20
RS232 Modbus, PC Capture, or Printer.............................21
Remote Sensor Wiring.....................................................22
CPU Board Configuration.................................................23
OPERATION __________________________24
OPERATOR INTERFACE..........................................24
Interface Panel.................................................................24
D12 GAS TRANSMITTER.................................................24
Startup Review Sequence................................................25
Main Display Page...........................................................26
Five-minute Time-out Rule................................................ 26
Esc Key Operation (Main Display Page) ........................... 26
Fault Indication (Main Display Page)................................. 26
Main Reading...................................................................27
Variable Editing................................................................28
SENSORS AND GENERATORS ........................................29
Sensor Setup...................................................................29
Sensor Setup Page........................................................... 29
Sensor More Page............................................................ 30
Sensor More Page............................................................ 30
Bump-Testing ..................................................................31
Calibration........................................................................32
Calibration Frequency....................................................... 32
Calibration Terminology.................................................... 32
Zero Calibration................................................................ 32
Span Calibration............................................................... 32
Calibration Kits.................................................................. 32
Indications During Sensor Calibration ............................... 32
Calibration Exceptions ...................................................... 32
Zero Calibration Procedure............................................... 33
Span Calibration Procedure.............................................. 34
Spanning for OTM Gases (Other Than Methane).............. 35
Spanning for Safety –Combustible Sensor Only............... 35
Sensor Calibration Records.............................................36
Auto-test ..........................................................................37
Auto-test Control Page...................................................... 38
Auto-test Setup Page........................................................ 38
Auto-test Setup Options Page........................................... 39
Next Auto-test Page.......................................................... 39
Auto-test History Page...................................................... 40
Gas Generator Page........................................................ 40
Auto-test Sequence .......................................................... 40
ALARMS AND RELAYS..............................................42
Gas Concentration Alarms...............................................42
Manual Alarm Reset ......................................................... 42
Remote Reset................................................................... 42
Gas Alarm Setup Pages.................................................... 43
Alarm Variable Functions.................................................. 46
Fault Alarms.....................................................................47
Corrective Actions............................................................. 47
Alarm Relays .................................................................... 50
Relay Setup Page............................................................. 51
Testing Alarm Relays........................................................ 51
Relay Test Page............................................................... 51
Inhibiting Alarms ..............................................................52
Alarm Inhibit Setup page................................................... 52
4-20MAOUTPUT ..........................................................53
Output Overrides............................................................... 53
4-20mA Setup Page.......................................................... 53
4-20mA Control Page........................................................ 54
Loop Adjustment............................................................... 54
DATA LOG.................................................................55
Data-log Access Page....................................................... 55
Data-log Setup Page......................................................... 55
Data-log Graphic Report Page.......................................... 56
Data-log Tabular Report Page .......................................... 56

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
5
Data-log Printout ...............................................................57
DISPLAY....................................................................58
Display Setup Page...........................................................58
SYSTEM.....................................................................59
System Access Page ........................................................59
Real-time Clock................................................................59
Clock Setup Page..............................................................59
Security............................................................................60
Security Control Page .......................................................60
Activating Security.............................................................60
Deactivating Security.........................................................61
Changing the Password ....................................................61
Communications..............................................................62
Communication Setup Page..............................................62
ASCII ................................................................................63
HART................................................................................63
Modbus.............................................................................65
Transmitter Version..........................................................65
Restart .............................................................................66
Resets..............................................................................66
SPARE PARTS ________________________ 67
APPENDIX A. _________________________ 68
PRINTING DATA LOG REPORTS .....................................68
Serial Connection.............................................................68
Communication Setup Page............................................68
Flow Control.....................................................................68
Report Format..................................................................69
Report Control .................................................................69
EXAMPLE:CHARTING A DATA LOG REPORT ..................70
Starting the Report...........................................................73
Charting with Microsoft Excel...........................................76
List of Figures
Figure 1. D12 transmitter....................................................................5
Figure 2. Combustible gas sensor ......................................................5
Figure 3. Combustible sensor with gas generator...............................5
Figure 4. Wheatstone bridge circuit ....................................................6
Figure 5. Overall Dimensions-Non Autotest Version (ATI-0587) .......10
Figure 6. Overall Dimensions- Autotest Version (ATI-0588)...............10
Figure 7. Separating the board stack................................................11
Figure 8. Power supply board connections .......................................12
Figure 9 Relay Contacts...................................................................13
Figure 10. ATI A17/B14 Example .....................................................14
Figure 11. Power Without 4-20mA Signaling Example......................15
Figure 12. 4-20mA Signaling, Single Supply, 3-Wire Example..........16
Figure 13. 4-20mA Signaling, Dual Supply, 4-Wire Example.............17
Figure 14. HART Transmitter, Point-to-Point, 3-Wire Example..........18
Figure 15. HART Transmitter, Multi-drop, 3-Wire Example...............19
Figure 16. RS485 Modbus Multidrop Example..................................20
Figure 17. RS232 Modbus, PC Capture, Printer Example.................21
Figure 18. Remote Sensor Wiring (ATI-0592)...................................22
Figure 19. CPU Board configuration.................................................23
Figure 20. Operator interface panel..................................................24
Figure 21. Startup review sequence .................................................25
Figure 22. Main display ....................................................................26
Figure 23. Standard fault indication ..................................................26
Figure 24. Variable editing ...............................................................28
Figure 25. Sensor setup page...........................................................29
Figure 26. Data-log warning page.....................................................29
Figure 27. Sensor “more” page.........................................................30
Figure 28. Zero calibration................................................................33
Figure 29. Zero_Sensor page...........................................................33
Figure 30 Span calibration................................................................34
Figure 31. Span_Sensor page..........................................................34
Figure 32. Sensor calibration history page........................................36
Figure 33. Combustible sensor with auto-test option.........................37
Figure 34. Auto-test control page......................................................38
Figure 35. Auto-test setup page........................................................38
Figure 36. Auto-test sequence......................................................... 41
Figure 37. Default alarm relationships for combustible gas sensors. 42
Figure 38. Manual alarm reset ......................................................... 42
Figure 39. Alarm setup pages (example).......................................... 43
Figure 40. Rising alarm (Active=ABOVE_SP, Reset=AUTO) ........... 46
Figure 41. Falling alarm (Active=BELOW_SP, Reset=AUTO).......... 46
Figure 42. Fault alarm (Main Display) ..............................................47
Figure 43. Fault page....................................................................... 47
Figure 44 Alarm relay schematic....................................................... 50
Figure 45. Relay setup page (example)............................................ 51
Figure 46. Relay test page example................................................. 51
Figure 47. Inhibiting alarms from the Main Display........................... 52
Figure 48. Alarm inhibit setup page.................................................. 52
Figure 49. Current loop output plot...................................................53
Figure 50. 4-20mA setup page......................................................... 53
Figure 51. 4-20mA control page.......................................................54
Figure 52. Loop adjustment pages...................................................54
Figure 53. Data log access page...................................................... 55
Figure 54. Data log setup page........................................................ 55
Figure 55. Data log graphic report page...........................................56
Figure 56. Data log tabular report page............................................56
Figure 57. Data-log printout..............................................................57
Figure 58. System access page....................................................... 59
Figure 59. Clock setup page............................................................59
Figure 60. Security control page ......................................................60
Figure 61. Activating security........................................................... 60
Figure 62. Deactivating security....................................................... 61
Figure 63. Changing the password................................................... 61
Figure 64. Communication setup page.............................................62
Figure 65. Hart setup pages............................................................. 63
Figure 66. Hart a) Find-me and b) Device found pages.................... 64
Figure 67. Modbus setup page......................................................... 65
Figure 68. Transmitter version page................................................. 65

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
5
INTRODUCTION
COMPONENTS
D12 LEL Transmitter
The D12 LEL Transmitter is used to monitor for gas leaks near storage
cylinders, process piping, or gas feed equipment in virtually any type
of industrial plant environment. Enclosed in an explosion proof
housing, it is rated for use in hazardous locations (see specifications).
The transmitter features a combustible gas sensor, a non-intrusive, four
button interface with back-lighted graphics, three level alarms with
three (optional) alarm relays, high-resolution 4-20mA current loop
output, real-time clock, data-logger, and optional HART™ or
Modbus™ communication interface. In addition, the sensor may be
ordered with an optional gas generator for automatic, timed testing of
the sensor. Figure 1. D12 transmitter
The Combustible Gas Sensor
The sensor components are housed in an explosion proof, stainless steel body that is threaded into the
base of the transmitter (or remote housing, if ordered). A porous, stainless steel flame arrestor is
welded to the exposed end to permit gas entry and to prevent possible ignition of a combustible
atmosphere. Threads are cut around the exposed end to accommodate accessories, such as rain shields,
and calibration adapters.
Active Element
The sensor’s active element is a catalytic bead, which generates heat by oxidizing
combustible gas on its surface. This “self-heating” raises the element’s
temperature and increases the internal resistance, in proportion to the gas
concentration.
Reference Element
The reference element is similar to the catalytic bead,
but it is inert to combustible gas and acts as a
reference to air temperature, and other ambient
conditions.
Figure 2. Combustible gassensor
Auto-test Option
When the Auto-test option is ordered for the combustible sensor, the
components are housed in a sensor body that includes a gas generator cell.
At a programmed interval and time-of-day, a small current is passed
through the cell to liberate a combustible gas. As the volume of gas
increases, it fills the cell cavity and travels up a short column that empties
onto the face of the sensor. The current is turned off when the transmitter
reading rises by a prescribed amount. If the sensor fails to respond, the
transmitter (optionally) activates the fault alarm.
Figure 3. Combustible sensor with gasgenerator
D12 GAS Transmitter

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
6
Catalytic
Bead
Reference
V
Bridge
+V
The sensor elementsare combined to form a Wheatstone
bridge, asshown in
Figure 4. Gas concentration is computed in proportion to the
voltage developed across the bridge, which is read by
transmitter’s CPU. The CPU linearizes the bridge voltage into a
gas concentration reading, and displays it in units of %LEL.
Figure 4. Wheatstone bridge circuit
Gas Mixtures
Rarely are pure gases required for calibration. Instead, gas mixtures are compressed into cylinders and
purchased as calibration gas sources. Mixtures are formed by combining a volume of component gas
with a volume of balance (or background) gas, and expressed as a ratio or percentage. For example, a
mixture containing 0.025 cubic feet of Methane, and 0.975 cubic feet of air would form a 2.5%
volumetric mixture of Methane in air:
2.5% = 0.025 / (0.025+0.975) * 100
The resulting mixture might be labeled as, “0.025Vol Methane/Bal. Air”, or “2.5%Vol Methane/Bal.
Air”, or “50%LEL Methane/Bal Air” (%LEL units are described below). Throughout this manual, air
is assumed to be the balance gas, allowing labels like the above to be shortened to “2.5%Vol Methane”,
and “1.1%Vol Propane”, etc. Also note that air is usually a mixture of 20.9% Oxygen/Bal. Nitrogen.
LEL, UEL
Combustible gases become explosive when mixed with air at a concentration known as the LEL (Lower
Explosive Limit). As more gas is mixed with air, the concentration rises, and remains explosive, until it
reaches the UEL (Upper Explosive Limit). Above the UEL, the concentration is considered non-
explosive.
The LEL and UEL vary from gas to gas. For example, the LEL of Methane is 5%Vol, while the LEL
of Propane is only 2.2%Vol. Likewise, the UEL of Methane is 15%Vol, compared to only 10%Vol for
Propane.
%LEL
By default, the transmitter reports combustible gas concentrations as a percentage of the LEL of
Methane, or %LEL Methane. Since Methane has an LEL of 5.0%Vol, a 2.5%Vol of Methane is
reported as 50%LEL:
50%LEL = 2.5%Vol / 5.0%Vol * 100
A reading at or above 100%LEL indicates a dangerous, explosive environment exists at the transmitter.
Every effort to evacuate personnel and prevent ignition should be taken.
OTM Gases (Other Than Methane)
Unless otherwise noted, the combustible gas sensor is calibrated for Methane. Since the sensor cannot
distinguish between different gases, exposure to any other combustible gas will result in erroneous
readings, and may present a dangerous condition. This condition may be corrected by recalibrating the
sensor’s scale, or “span”. See Spanning for OTM Gases (Other Than Methane).

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
7
Multiple Gas Safety
Due to differences in LEL and oxidation rates between gases, it is usually best to avoid situations where
the sensor may be exposed to more than one combustible gas at the same time. In situations where it
cannot be avoided, the sensor should be calibrated to provide the highest margin of safety. See
Spanning for Safety.
Oxygen is Essential
Oxygen is essential for the sensor to function. As mentioned above, the catalytic bead oxidizes, or
burns, a very small amount of the gas it is intended to measure. Therefore, the sensor must not be used
in oxygen-depleted environments. Furthermore, higher concentrations of gas imply lower
concentrations of oxygen, so the sensor must not be used to monitor concentrations that might exceed
the LEL of the gas.
Gas Flooding
A gas leak in a confined space may eventually decrease the transmitter reading as oxygen is displaced,
resulting in an undetectable, explosive condition. For this reason, the transmitter latches the reading at
100%LEL, and holds it until manually reset. Relay RL3 is assigned to the high alarm, labeled Alarm,
which is set to activate at 50%LEL and remain active until manually reset. Alarms derived from the
current loop output should also require manual reset, and be configured to activate at or below
60%LEL.
Compounds to Avoid
Silicon
Catalytic bead sensors are adversely affected by silicon, such as might be present in lubricants and
sealants. High concentrations of silicon vapor can cause complete loss of sensitivity in as little as a few
hours. These sensors should not be used where silicon vapors are normally present and sensors should
be protected from these vapors if such compounds are in use temporarily.
Hydrogen Sulfide
Hydrogen sulfide will reduce sensitivity after a few weeks of exposure, but will usually level out. The
effects may be compensated for by spanning the sensor (see Span Calibration).
Lead
While not commonly encountered, exposure to lead compounds may result in a total loss of sensitivity.
The sensor must not be used in
oxygen-depleted environments.
The sensor must not be used to
monitor concentrations of gas that
exceed the LEL.
Avoid exposing the sensor to Silicon-based compounds, Hydrogen
Sulfide, and Lead compounds.
Do not enter any area reporting an alarm until confirming
independently it is safe to do so.

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
8
SPECIFICATIONS
Table 1. Specifications
Gas Type
Combustible gas such as Methane, Propane, Butane, plus many more, including
Ammonia and Hydrogen
Sensor Type
Catalytic bead for combustible gas, 316 stainless steel housing
Range
50 –100% LEL
Response Time
T90 in 10 seconds
Accuracy
±1% LEL
Repeatability
±1% (Electronic)
Linearity
±0.5% (Electronic)
Zero Drift
Less than 2% full scale per month
Span Drift
Dependent on operating environment but generally less than 3% per month
Analog Output
4-20 mA, 675 ohms max. at 24 VDC
Serial
Interface
HART® (1200 baud Bell 202 modem interface)
Modbus ® (1200-9600,14.4k,28.8k, RS232 or RS485)
ASCII datalogger output
Power
12 –30 VDC, 250 mA maximum
Alarm Relays
Three SPST, 5 A @ 250 VAC resistive
Relay Coil
Programmable either normally energized or normally de-energized.
Enclosure
Explosion-proof, Class 1, Div. 1, Groups B, C, & D.
Auto-Test
Optional
Display
Graphics LCD, 96w x 32h, back-lighted
Controls
Four button, non-intrusive (magnetic switches); remote alarm reset input
Operating Temp
-40° to +75° C
Weight
4 Lbs. (1.8 Kg.)
Remote Sensor
Optional, 25ft Max.

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
9
INSTALLATION
MECHANICAL MOUNTING
Transmitter
Figure 5 shows the
dimensions of the
transmitter enclosure and
the location and size of
the electrical conduit
connection. In locations
classified as hazardous
(explosive), the transmitter housing must be earth grounded, and an explosion-proof seal must be
installed as required by the local electrical code. The conduit or cable gland entry into the enclosure
must be sealed. If conduit is used, it must also be sealed internally at the housing entry. This is
required to prevent condensation from draining into the enclosure.
Seal conduit inside and out to keep out water.
Follow national, state, and local, electrical codes.
Secure the transmitter to a wall or flat surface through two mounting holes in the enclosure, as shown in
Figure 5 and Figure 6. If appropriate fasteners are used, the transmitter may be supported by conduit
alone.
The transmitter should be mounted with the sensor facing down. Transmitters are shipped with a
protective plastic cap over the sensor that should be left in place during installation, and removed before
placing the transmitter in service (leave the cap installed whenever painting around the transmitter).
HAZARDOUS LOCATIONS
Connect housing to earth ground. Use explosion
proof conduit, and seal it inside and out.
Follow national, state, and local, electrical codes.

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
10
Figure 5. Overall Dimensions-Non Autotest Version (ATI-0587)
Figure 6. Overall Dimensions- Autotest Version (ATI-0588)
D12 GAS TRANSMITTER
D12 GAS TRANSMITTER

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
11
ELECTRICAL CONNECTIONS
The Stack
The transmitter consists of three circuit boards, known collectively as the “stack”. From top to bottom,
they are the, Display, CPU, and Power Supply. The top two boards, Display and CPU, are fastened
together with metal standoffs, and plug into the Power Supply board, which is fastened to the lower
housing with similar metal standoffs. Since most external wiring connections are made to terminals on
the Power Supply board, it will be necessary to remove the top two boards.
Grasp the outer edge of the metal faceplate covering the Display board and gently rock it side to side,
while pulling it up and away from the housing. Once the top two boards come free, lift them out and
disconnect the sensor ribbon cable (note: this connector is keyed for ease of reconnecting later).
Figure 7. Separating the board stack
External Power Supply
The transmitter requires a regulated DC supply, operating between 12 and 30 VDC. Transmitters
ordered with relays will require a maximum current of 250mA, worst case (all relays energized).
Power supplies for operating multiple units should be sized for twice the calculated load to allow for
start-up (inrush) current.
Please be aware of the hidden ribbon cable that connects the top two boards to the lower board.
This cable is long enough to permit the boards to come free from the housing, but no further.
D12 GAS
TRANSMITTER
Set switch SW5 to OFF before removing
the upper board stack from the transmitter.
Since SW5 does not disconnect power at
the terminals of the Power Supply Board,
declassify hazardous areas prior to
opening the transmitter housing.
Display
Board
CPU
Board
Power
Supply
Board
Ribbon
Cable
Standard
Combustible Sensor
Combustible Sensor
with Auto-test

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
12
TB2 (Optional Relay
Connections)
T
B1
(Pow
er,
Analo
g/Digi
tal
I/O)
Power Supply Board
Electrical connections are made to terminal blocks TB1 and TB2. The 4-20mA current loop, optional
digital communications, and remote alarm reset, are connected at TB1. Connections to the three
optional relays are made at TB2. It is recommended to power the transmitter, and all controls and
indicators, from separate, uninterruptable supplies.
Note: This version of the transmitter cannot operate on loop power alone.
The transmitter requires primary
power in the range of 12 to 30 VDC
applied to pins 7 and 8 on TB1.
Current loop operation requires
power in the same range on pin 5
(mA+), from which the
transmitter sources a positive,
4-20mA output on pin 6 (mA-).
IMPORTANT
The loop supply voltage on pin
5 must not exceed the primary
supply voltage on pin 8.
Figure 8. Power supply board connections
In 3-wire mode, the transmitter requires a maximum of 250 mA, with all relays active. Power supplies
operating multiple units should be sized for twice the calculated current requirement to allow for inrush
current during startup.
The housing has limited space for wire. Use the smallest gauge wire available that is compatible with
electrical code and current requirements. When powering a group of transmitters in 3-wire mode from
the same power supply, 12 AWG wire is recommended for long runs, with smaller (higher gauge) wire
drops to each transmitter.
Internal relays are best used as pilot relays if heavy load switching is required. Use suitable arc
suppression devices across loads switched through internal relays.
The transmitter housing may be grounded through explosion proof conduit. In the absence of such
conduit, use a suitable grounding strap to bond the transmitter’s housing to earth ground.
Always follow wiring practices governed by local, state, and national electrical codes.

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
13
Relay Contacts
Note: the behavior described below is determined by the default relay settings, which may be
reprogrammed through the operator or communication interface.
By default, RL1 is de-energized until the gas concentration reaches the Warning level, and is then
energized until the alarm is cleared, or power fails. Likewise, RL2 is de-energized until the gas
concentration reaches the Alarm level, and is then energized until the alarm is cleared, or power fails.
In contrast, RL3 is energized until a Fault condition is detected, or power fails, and is then de-energized
until the condition is cleared.
Figure 9 Relay Contacts
NO
NC
C
NO
NC
C
NO
NC
C
RL1
(Default = WARNING)
RL2
(Default = ALARM)
RL3
(Default = FAULT)
PC
PNO
PNC
PC
PNO
PNC
PC
PNO
PNC
To controls or
indicators activated by
RL1
To controls or
indicators activated by
RL2
To controls or
indicators activated by
RL3
PC = Power supply or return
applied to common contact.
PNO = Power supply or return
applied to NO contact during
relay activation.
PNC = Power supply or return
removed from NC contact
during relay activation.

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
14
Wiring Examples
ATI A17/B14, 3-Wire Mode
A single ATI A17 Power Supply may be used to power one ATI B14 Receiver with single D12-17
transmitter, as shown below.
Figure 10. ATI A17/B14 Example

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
15
Power Without 4-20mA Signaling
Power without 4-20mA signaling is not common practice, except when signaling digitally over HART
multidrop and Modbus connections. There are several examples of those in the pages that follow.
When 4-20mA signaling is not used, the transmitter may be powered from TB1-5,6,7,and 8, which are
connected directly to the supply (note 1). Multiple transmitters may be powered this way, as shown.
Size each power supply according to the number of transmitters, the current demand of each (see
specifications), and the wire resistance. The wire resistance must not be allowed to drop the primary
supply voltage below 12V at the primary supply terminals of any transmitter. Hint: If possible, use 12-
14 AWG wire on primary supply connections, keep the number of transmitters low, and verify the
voltage on the on the transmitter furthest from the supply.
Figure 11. Power Without 4-20mA Signaling Example
Notes
1. Power without 4-20mA signaling is not common practice, except for HART multidrop or Modbus
connections that use digital signaling (not shown), providing a local alarm, or both. Power shown above
is sufficient for Modbus connections, relays, and LCD backlight operation.
-
Primary Supply Voltage
(12v Minimum)
+
+
24
-
+
TB1
TB1
Primary Supply
12 to 30 VDC
+
-

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
16
4-20mA Signaling, Single Supply, 3-Wire Mode
The transmitter will source current to a loop receiver as shown. A single power supply provides both
primary and loop power to the transmitter. Size each power supply according to the number of
transmitters, the current demand of each (see specifications), and the wire resistance. The wire
resistance must not be allowed to drop the Primary Supply Voltage below 12V at the terminals of any
transmitter. Hint: if possible, use 12-14 AWG wire on supply connections (shown in bold).
Figure 12. 4-20mA Signaling, Single Supply, 3-Wire Example
-
Primary Supply Voltage
(12v Minimum)
+
+
Multichannel Current
Loop Receiver with
Integral 24V Supply
(Channels are
typically not isolated
from supply)
-
+
-
+
+
24
G
nd
Sig
TB1
-
+
0.0
Sig
TB1
+24

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
17
4-20mA Signaling, Dual Supply, 4-Wire Mode
To reduce the power requirement of a single current loop supply, the transmitter may be powered from
both a primary and loop supply, providing the following conditions are met.
1. Supply grounds are directly connected to minimize ground loops, and,
2. The Primary Supply Voltage must not drop below the Loop Supply Voltage, as measured at
instrument terminals.
Size each power supply according to the number of transmitters, the current demand of each (see
specifications), and the wire resistance. The wire resistance must not be allowed to drop the Primary
Supply Voltage below the Loop Supply Voltage, as measured at the terminals of any transmitter. Hint:
select a Primary Supply with a higher voltage output than the Loop Supply, and use 12-14 AWG wire,
if possible. Keep the number of transmitters supplied by the Primary Supply low, and verify the
voltages at the terminals of the transmitter furthest from the Primary Supply.
Figure 13. 4-20mA Signaling, Dual Supply, 4-Wire Example
I M P O R T A N T
Primary Supply Voltage
must not drop below Loop
Supply Voltage at terminals
of any transmitter.
Hint: Use 12 AWG wire on
Primary supply connections
to minimize voltage drops.
Connect supply commons to
minimize ground loops and
voltage drops that might
reduce the Primary Supply
Voltage below the Loop
Supply Voltage, at transmitter.
Select a Primary Supply with a
higher voltage output, and,
1
2
-
Primary Supply Voltage
Loop Supply Voltage
(Vprimary >= Vloop >=12v)
+
+
Primary Supply
24 to 30 VDC
30.0
-
+
-
+
0.0
-
+
0.0
Sig
-
+
+24
Gnd
Sig
P
rim
ary
Su
ppl
y 1
2 to
30V
DC
TB1
TB1
Multichannel Current Loop Receiver with Integral 24V Supply
(Channels are typically not isolated from supply)

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
18
HART Transmitter, Point-to-Point, 3-Wire (Active Source)
The HART “Point-to-Point” connection permits the transmitter to communicate digitally, while
retaining the functionality of its 4-20mA current loop. Setting the transmitter’s polling address to 0
permits the current loop to function normally. According to HART specifications, the current loop
must be terminated with a load resistor between 230 and 1100 ohms; however, transmitter
specifications restrict the maximum analog output resistance to a lower value (see Specifications). The
term, “active source”, refers to a transmitter that is not loop powered, and sources current from power
applied to it on separate terminals. Size the power supply according to the number of transmitters, the
current demand of each transmitter (see specifications), and wire resistance. Wire resistance must not
be allowed to drop the Primary Supply Voltage below 12V at the terminals of any transmitter. Hint:
use at least 14 AWG wire on supply connections (shown in bold).
Figure 14. HARTTransmitter, Point-to-Point, 3-Wire Example
-
Primary Supply Voltage
(12v Minimum)
+
+
Current Loop Receiver/Alarm Module
with Integral 24V Supply
For Digital and Analog Signaling
Channels are typically not isolated
from the supply, and must include
appropriately sized load resistor
between 230 ohms, and the maximum
analog output resistance stated in the
transmitter specifications.
-
+
+24
Gnd
TB1
Bell202
Modem
Optional
Barrier/Isolator
for Hazardous
Locations
DCS or SCADA System
(primary master)
Hand-held Communicator
(secondary master)
-
+
0.0
-
+
+24
Gnd
Sig
Load Resistor for
Digital Signaling Only
Or

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
19
HART Transmitter, Multi-drop, 3-Wire (Active Source)
The HART “Multi-drop” connection permits up to 15 transmitters to communicate digitally on the
same bus, but at the cost of analog current signaling. Setting the transmitter’s polling address from 1 to
15 fixes the current loop output at 4mA. According to HART specifications, the current loop must be
terminated with a load resistor between 230 and 1100 ohms; however, transmitter specifications restrict
the maximum analog output resistance to a lower value (see Specifications). The term, “active source”,
refers to a transmitter that is not loop powered, and sources current from power applied to it on separate
terminals. Size the power supply according to the number of transmitters, the current demand of each
transmitter (see specifications), and wire resistance. Wire resistance must not be allowed to drop the
Primary Supply Voltage below 12V at the terminals of any transmitter. Hint: use at least 14 AWG wire
on supply connections (shown in bold).
Figure 15. HARTTransmitter, Multi-drop, 3-Wire Example
-
+
+24
Gnd
Bell202
Modem
DCS or SCADA System
(primary master)
Load Resistor for
Digital Signaling Only
-
Primary Supply Voltage
(12v Minimum)
+
+
Hand-held Communicator
(secondary master)
Optional
Barrier/Isolator
for Hazardous
Locations
TB1
TB1
TB1
4mA
4mA
4mA
12mA

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
20
RS485 Modbus Multidrop
RS485 operation requires the transmitter to be wired in 3- or 4- wire mode. In addition, the RS485 or
RS485 UNTERMINATED COM jumper must be installed at JP4 on the CPU. Modbus permits up to
247 devices to communicate digitally on the same bus; however, RS485 limits this to 32. Refer to the
Modbus Interface Manual for details on Modbus connections and implementation.
Figure 16. RS485 ModbusMultidrop Example
Common
B(+)
A(-)
DCS, SCADA, or
Computer System
(Modbus master)
Primary Supply
12 to 30 VDC
3
0.0
+
-
24
TB1
N
3-Wire Transmitters
TB1
3-Wire Transmitter
(furthest from master)
1
Common
B(+)
A(-)
Common
B(+)
A(-)
RS485
Unterminated
Install RS485 Unterminated jumper
block on all CPU boards except on
transmitter furthest from master.
Install RS485 jumper block
on transmitter furthest from
master.
RS232-to-RS485 Adapter
RS485
+
-
Primary Supply Voltage
(12v Minimum)

Series D12 LEL Gas Transmitter with Catalytic Bead Sensor
Revision J (July 15)
21
RS232 Modbus, PC Capture, or Printer
RS232 operation requires the transmitter to be wired in 3- or 4- wire mode. In addition, the RS232
COM jumper must be installed at JP4 on the CPU board. The RS232 connection may be used for a
Modbus connection, capturing the data log output using a PC, or printing the data log output to an
Epson compatible printer. Refer to the Modbus Interface Manual for details on Modbus connections
and implementation, and to Appendix A. on page 68 for details on outputting data log reports.
Figure 17. RS232 Modbus, PC Capture, Printer Example
DCS, SCADA, or
Computer System
(Modbus master or
terminal program)
Primary Supply
12 to 30 VDC
3
0.0
+
-
24
TB1
3-Wire Transmitter
Sig.Gnd
Rx
Tx
RS232
Install RS232 jumper
block on CPU board.
DB9 Female
5
3
2
-
Primary Supply Voltage
(12v Minimum)
+