Omniguard 760 series Service manual

760 SERIES OPTICAL
FLAME DETECTORS
Installation and operating
service manual

2
©Firey AB (Oktober 2016)
Table of contents
Description ...........................................................................3
Theory of operation ...................................................................5
Specications .........................................................................6
Applications ..........................................................................7
Installation............................................................................7
Electronics ............................................................................7
Maintenance and troubleshooting....................................................11
Service and Repair ...................................................................12
Warranty.............................................................................12
Part Number Key .....................................................................13
Wiring Diagram ......................................................................13
CAUTION!
Electrostatic Discharge:
A discharge of static electricity from an ungrounded source, including the human body,
may damage the electronic circuitry of the Omniguard® Series 760 Flame Detectors. Use
one or more of the following methods when handling or installing electrostatic sensitive
parts:
• A wrist strap connected by a ground cord to an earth ground source
• Heel straps, toe straps, or boot straps at standing workstations
• Conductive eld service tools
• A portable eld service kit with a static-dissipating work mat

3
©Firey AB (Oktober 2016)
Description
The Omniguard® 760 ame detector is an optically based,
self-contained, microprocessor controlled, multi-spectrum
infrared (IR5) ame detector. The 760 ame detector utilizes
the patented Fire Event Analysis (FEA)™ discrimination
technology. This ame detector is compatible with most alarm
panels without the need for a controller. All electronics are
housed within a copper-free aluminum, high temperature,
TGIC-Polyester coated enclosure with a ¾-14NPT or M20-1.5
conduit entry.
The Model 760 ame detector is suitable for use in Class I,
Division 1, Groups B, C and D (explosion-proof) areas. The
housings are Type 4X, dust-tight and watertight. The detectors
are approved for both indoor and outdoor installations.
Standard features
• Microprocessor Based.
• User adjustable time delays.
• User adjustable latching or non-latching re relay.
• User adjustable sensitivity.
• User adjustable NO or NC relay outputs.
• LED indication: re (red), normal (green ashing), fault (amber).
• Transient voltage (surge) protection.
• RS485 addressable user interface using MODBUS RTU.
• Terminal block accepts 22 to 12 AWG wire.
• 0 to 20 mA output.
• Relay contacts rated at 2 Amps @ 30 VDC.
Approval:
• FM
• SIL 2
• CSA
• Russian Fire Certicate
• IECEx
• ATEX
• EMC
• LVD
• CSFM
Fire Detection Performance
The Model 760 ame detector is designed to function properly
when operated under the conditions outlined in the“re detetion
performance”, “false alarm immunity”and “re detection in the
presence of false alarm sources” sections of this manual. Exposing
a 760 detector to any IR sources within the specied eld of view at
distances less than 3.5 feet may cause the detector to either false
alarm or alter the detector’s abiltiy to meet other stated performance
parameters during the exposure.
Note: All performance tests listed below were performed outdoors
and were third party certied for performance. The “*“ indicates a pre-
burn condition.
Normal Sensitivity:
• 1 ft2n-Heptane re at 75 ft in < 1 sec.
• 1 ft2gasoline re at 75 ft in < 1 sec.
• 1 ft2Isopropyl Alcohol re at 75 ft in < 1 sec.
• 1 ft2Propane re at 75 ft in < 1 sec.
• ½ lb of oce paper re at 75 ft in < 1 sec.*
• 0.75 inch diameter orice with a ow rate of 1.5 SCFM hydrogen
plume at 50 ft < 1 sec.
• 1 ft2Diesel re at 75 ft in < 1 sec.*
Enhanced Setting:
• 1 ft2n-Heptane re at 100 ft in < 1 sec.
• 1 ft2gasoline re at 100 ft in < 1 sec.
• 1 ft2Isopropyl Alcohol re at 100 ft in < 1sec.
• 1 ft2Propane re at 100 ft in < 1 sec.
• ½ lb of oce paper re at 100 ft in < 1 sec.*
• 1 ft2Diesel re at 75 ft in < 1 sec.*
Long Distance Setting:
• 1 ft2n-Heptane re at 200 ft in < 1 sec.*
• 1 ft2gasoline re at 200 ft in < 1 sec.
• 1 ft2Propane re at 200 ft in < 1 sec.
• 4 ft2JP5 re at 200 ft in < 5 sec.*
• 4 ft2Diesel re at 200 ft in < 5 sec.*
Note: Detector response times and distances can be inuenced by
wind, smoke and viewing angle. Consult Firey AB applications
engineers for specic details.

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©Firey AB (Oktober 2016)
False Alarm Immunity
All tests were performed outdoors and third party certied for no
response at the recommended distances. These distances should be
used as a guide when installing the detectors.
Normal Sensitivity:
• Sunlight
• 1500 Watt ribbon heater at 5 ft.
• 100 Watt incandescent bulb in a work-light xture at 3.5 ft.
• 500 Watt quartz halogen lighting xture at 4 ft.
• 40 Watt uorescent bulb at 4 ft.
• Welding at 20 ft.
Enhanced Sensitivity:
• Sunlight
• 1500 Watt ribbon heater at 7 ft.
• 100 Watt incandescent bulb in a work-light xture at 5 ft.
• 500 Watt quartz halogen lighting xture at 4 ft.
• 40 Watt uorescent bulb at 4 ft.
• Welding at 20 ft.
Long Distance Sensitivity:
• Sunlight
• 1500 Watt ribbon heater at 10 ft. (unmodulated)
• 1500 Watt ribbon heater at 20 ft. (modulated)
• 100 Watt incandescent bulb in a work-light xture at 10 ft.
• 500 Watt quartz halogen lighting xture at 5 ft.
• 40 Watt uorescent bulb at 4 ft.
• Welding at 40 ft.
Note: Unless otherwise specied the method of testing for sunlight
was both direct and indirect and for the other sources was both
modulated and unmodulated.
Fire Detection Performance in the Presence of False Alarm
Sources
All tests were performed outside and third party certied for response
to a 1 ft2Propane re at 75 ft for the Normal setting, at 100 ft for the
Enhanced setting and at 200 ft for the Long Distance setting with the
false alarm sources at the recommended distances. In all cases the
detector response was less then 1 second. These distances should be
used as a guide when installing the detectors.
Normal Sensitivity:
• Sunlight
• 1500 Watt ribbon heater at 5 ft.
• 100 Watt incandescent bulb in a work-light xture at 3.5 ft.
• 500 Watt quartz halogen lighting xture at 4 ft.
• 40 Watt uorescent bulb at 4 ft.
• Welding at 20 ft.
Enhanced Sensitivity:
• Sunlight
• 1500 Watt ribbon heater at 10 ft.
• 100 Watt incandescent bulb in a work-light xture at 5 ft.
• 500 Watt quartz halogen lighting xture at 4 ft.
• 40 Watt uorescent bulb at 4 ft.
• Welding at 20 ft.
Long Distance Sensitivity:
• Sunlight
• 1500 Watt ribbon heater at 20 ft.
• 100 Watt incandescent bulb in a work-light xture at 10 ft.
• 500 Watt quartz halogen lighting xture at 5 ft.
• 40 Watt uorescent bulb at 4 ft.
• Welding at 40 ft.
Note: Unless otherwise specied the method of testing for
sunlight was both direct and indirect and for the other sources was
unmodulated only.
(Fig 1) Field of View for JP-5
(Fig 2) Field of View for Diesel
(Fig 3) Field of View for all other Tested Fuels

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©Firey AB (Oktober 2016)
Theory of operation
The Omniguard® 760 ame detector is a multi-spectrum, infrared
sensing, re detector. The principle of operation is based on the
patented Fire Event Analysis (FEA) detection algorithm proven to be
both successful and reliable since its inception in 1984. The newly
developed 760 Flame Detector utilizes the fundamental concept of the
original FEA scheme while incorporating improvements aorded by
advances in microprocessor technology.
Sensors located behind two separate windows sample 5
separate wavelength regions within the infrared (IR) portion of
the electromagnetic spectrum. These sensors are continuously
interrogated to ensure the proper operation of the re detector.
The re channel senses radiation in two discrete regions of the IR,
which are common to the CO2and H2O emission bands generated as
by-products in conjunction with most combustion processes. The non-
re channel senses radiant energy in three additional discrete regions
of the IR, which are exclusive of those associated with the re channel.
The outputs from these sensors, combined with a sophisticated
algorithm, results in a highly reliable means with which to detect res
fueled by both hydrocarbon and certain non-hydrocarbon materials
while maintaining a high degree of false alarm immunity.
The automatic self-test feature of the Model 760 ame detector veries
the proper function of the electronics, sensors and optical surfaces.
This self-interrogation process is implemented a minimum of four
times per hour, thereby providing vital re detection reliability. This
is accomplished by channeling the calibrated output of an internally
mounted incandescent lamp, through optical light guides, to both
re detector windows and nally the sensors. Failure of this process
will generate a fault indication. Upon receipt of a fault, an inspection
process is required in order to determine whether the windows have
become contaminated to a level that is likely to impair the detector’s
ability to adequately sense res.
A self-test fault condition will result when a sensor’s response has
degraded signicantly over that established during the original factory
calibration of the re detector. Alternatively, in the event of a self-test
fault where windows are found to be free of lms, the fault will be an
indication that another part of the detector has failed.
The 760 ame detector has three sensitivity settings: Normal,
Enhanced and Long Distance. For performance attributes associated
with these settings please refer to section for User Selectable Interface
(USI) Options.
Note: Reference Figure 4 for appropriate sensor wavelength regions to
be used in Zeta calculations per NFPA 72 edition 2002 or later.
(Fig 4) Typical Hydrocarbon Fire Spectrum (Wavelengths in Micrometers)

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©Firey AB (Oktober 2016)
Specications
Environmental
• Suitable for use in hazardous locations:
Class I, Division 1, Groups B, C & D
Class II, Division 1, Groups E, F & G
Type 4X rated.
• European Rating –
ll 2 G/D Exd IIB + H2 T5 Gb for gas
Ex tb IIIC T100°C Db IP66 for dust
• Operating Temperature: -40°F to 194°F (-40°C to 85°C)
• Storage Temperature: -40°F to 212°F (-40°C to 100°C)
• Humidity: 0 to 95% relative humidity at 140°F (60°C)
• Shock: Mil-Std-810E Method 516.4 Procedure I, Figure 516.4-4, 20
G’s, 11ms
• Vibration: Mil-Std-810E Category 10, Method 514.4 Test Procedure
1, Test Condition I-3.4.9, Figure 514.4-17. Modied 20 to 500 HZ. 20
minute sweep to 3 Hrs Max per Axis in all three Axes.
Electical Interface
• Nominal voltage input – 24 Vdc (20 Min/30 Max).
• Maximum allowable ripple voltage – 240 mV
• Maximum Current Draw (@ 30Vdc):
Standby Alarm Manual Test Auto Test
80 mA 100 mA 160 mA 160 mA
• Relay Contact rating:
2 Amps @ 30 Vdc (Resistive)
Note: The detector contains two relays:
(1) Fire, (1) Fault
• Current Loop Output (0 to 20 mA) (For details see Table 2)
• RS485 Half-duplex, Addressable, User Interface
Baud Rate 9600 bits per second
1 start bit, 8 data bits and 2 stop bits.
• Maximum Power consumption (@ 30 Vdc)
Standby Alarm Manual Test Auto Test
2.40 W 3.00 W 4.80 W 4.80 W
Mechanical Specication
(Figure 5 Shows Nominal Dimensions)
Depth: 4.9 inches [124.97 mm](Max)
Height: 4.8 inches [122.43 mm](Max)
Width: 5.5 inches [140.21 mm](Max)
Weights: (installed)
Aluminum Housing 5 lbs (2.4 kg)
Stainless Steel 13 lbs (6.3 kg)
Shipping weight:
Aluminum Housing 6 lbs (2.8 kg)
Stainless Steel 14 lbs (6.7 kg)
Optional Accessories
Swivel Mount - 20856(1) (Used with aluminum enclosure)
70991(2) (Used with stainless steel enclosure)
Air Shield Kit - 19796
Rain Shield - 23546
Portable test unit  Model 545
(Fig 5) Mechanical Dimensions
(Fig 6) Swivel mount installation

(Fig 5) Mechanical Dimensions
Applications
The Model 760 ame detector is designed for re detection
applications where sudden res from hydrocarbon and specied non-
hydrocarbon fuels, may occur. This detector is not recommended for
detection of smoldering materials.
The following is a partial list of materials which when burned, can emit
infrared radiation in the wavelengths common to the detection bands
of the 760. Response times and detection distances will vary. Contact
a Firey AB applications engineer for assistance:
Hydrocarbon:
• Petroleum based materials such as liquid fuels, solvents, gases, or
solid compounds
• Wood products
Non-Hydrocarbon:
• Hydrogen, silane, hydrazine
The rugged, weatherproof construction and the operating
temperature range of the detectors will accommodate a variety of
indoor and outdoor applications.
All installations should comply with local re codes and regulations.
Do not proceed with the installation if you do not understand the
installation procedure or operation of the detectors. Firey AB
applications engineers are available to assist you.
Installation
To ensure trouble-free operation and reliable re protection, follow
these installation guidelines:
1. Locate the Detector(s) in an area where they will have an
unobstructed view of the area to be protected. The detector(s) must
be accessible for periodic cleaning. Failure to maintain clean sensor
windows and self-test optics will impair the performance of the
detector.
2. Separate the base from the housing by removing the four M8 X
1.25 cap screws. This will require a 6mm hex key. Store the housing
assembly, containing the electronics, in a clean and dry environment
while installing the base.
3. Mount the detector base to a previously installed swivel mount
or other appropriate support structure so that the detector has an
unobstructed view of the area to be protected. Position the base such
that the conduit opening faces down. It will be necessary to seal the
conduit within 18 inches of the re detector enclosure. This will insure
that water and airborne moisture do not enter the detector housing
through the conduit. Provide conduit drains as necessary to prevent
moisture from collecting inside the conduit.
4. Determine the critical areas where res are most likely to occur. Use
these areas as focal points for aiming the detectors. The detectors
have a conical eld-of-vision as shown earlier in Figures 1 and 2.
The type of fuel and the size of the re will determine the range of
detection. Aim the detector at a point equal to or below horizontal so
that water, dust and dirt will not accumulate on the optical surfaces
of the detector. As a general rule, mount the detector so that it will
view the base of the area to be protected. The aiming of the detectors
becomes increasingly critical the greater the detection distance
becomes. There should be few if any obstructions between the
detector and the area to be protected.
5. Complete the installation by wiring the detector according to the
wiring diagram located inside the rear cover. Before assembling the
detector housing to the base, verify that the terminal block assembly is
plugged in all the way and is located at the top. Insure that the wires
are arranged so as not to interfere with the main electronics module.
If a Torque wrench is available, it is recommended that the four cap
screws be tightened to a value of 35 to 40 in-lbs. (3.95 to 4.52 NM).
Note: The electronics module contains no re-useable parts. It should
never be removed from the housing assembly. This will result in the
voiding of the warranty.
6. Use a 20 to 30 Vdc regulated and ltered power supply, with a ripple
not exceeding 1 percent. The detectors should be protected from
induced and transient voltages as well as radio frequency interference
(RFI). To ensure compliance to CE requirements, a dedicated conduit is
highly recommended for the detector wiring. Connect every detector
base to earth ground via an independent wire. Earth ground and
-24 VDC RTN should be isolated and not connected anywhere in the
installation.
Electronics
User Selectable Factory Settings
The electronic module has been factory congured to provide the user
with the following:
Time Delay: 3 Seconds (re)
35 Seconds (Warning)
Sensitivity: Normal
Relays: Fire: Normally Open, Latching.
Fault: Normally Open, Non-latching (Relay is failsafe,
it closes upon application of power to
detector and will clear after a successful test).
Optical Self-Test: Automatic
0 to 20 mA: “OFF”
RS485: “OFF” MODBUS RTU
User Selectable Interface (USI) Options
Refer to Figure 8 for locations of User Selectable Interface Options.
Figure 7 provides the user with a quick reference of switch setting
options for the various models. The text following these gures
describes in more detail the function of each switch setting.
SPST dip switch (S1) located on rear I/O board
Option O On
Automatic & Manual Test Activated 1, 2
No Test Feature 1, 2
Manual Test Only 2 1
Automatic Test Only* 1 2
Sensitivity — Long Distance 3, 4
— Enhanced 3 4
— Normal 4 3
— (Reserved) 3, 4
Warning Alarm5 5
No Warning Alarm* 5
Fire Output Latching* 6
Fire Output Non-latching 6
0 to 20 mA 7
No 0 to 20 mA* 7
RS485 MODBUS RTU 8
No RS485 MODBUS RTU* 8
Program 9
No Program* 9
*Denotes factory settings for auto test units only
(Fig 7) Switch Options For the User Selectable Interface
7©Firey AB (Oktober 2016)

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©Firey AB (Oktober 2016)
(Fig 8) User Selectable Options
Fire Time Delay
The re outputs can be congured to delay for up to 25 seconds
before annunciation of a re. If the re were to extinguish anytime
prior to the end of the set delay time, the detector would not declare
a re. The factory setting for this delay time is 3 seconds. To adjust
the re delay time, use Potentiometer (Pot) R49. Turning the Pot
counterclockwise (CCW) will decrease the time delay. One turn equals
approximately 1.25 seconds.
Warning
Switch position 5 is used to enable the Warning Output. If switch
position 5 is “ON”, this option is activated. If switch position 5 is
“OFF”, this option is not activated. This option will alert the user to
the presence of elevated levels of IR within the eld-of-view of either
sensor.
Warning Time Delay
The warning outputs can be congured to delay for up to 60 seconds
before annunciating the presence of elevated IR levels. If the warning
signal disappears prior to the end of the set time delay, then the
detector would not allow the outputs to toggle“ON”. The factory
setting is 35 seconds. To adjust the warning time delay, use Pot R48.
Turning the Pot CCW will decrease the time delay. One turn equals
approximately three seconds.
Note: Always reset power to the detector after adjusting the pots. The
detector will not recognize any new setting unless it is reset.
Sensitivity Levels
(Table 1): Switch positions 3 and 4 adjust the sensitivity to four
dierent levels. The “Long Distance”setting is the most sensitive
to infrared radiation and the most susceptible to false alarms. The
“Normal” setting is the factory setting and is recommended for
most applications. The following are the settings for the two switch
positions:
Table 1: Sensitivity Settings
Sensitivity Level Position 3 Position 4
Long Distance O O
Enhanced O On
Normal On O
(Reserved) On On
Note: The “Reserved” setting will provide the same level as the
“Normal” setting.
Relay Adjustments
There are two relays and conguration option jumpers, JP1 and JP2,
located on the exposed surface of the printed circuit board (PCB) in the
housing assembly. Using these jumpers, the relays may be congured
as normally open or closed. The factory will ship the detectors with
the following settings.
Relay Adjustments
There are two relays and conguration option jumpers, JP1 and JP2,
located on the exposed surface of the printed circuit board (PCB) in the
housing assembly. Using these jumpers, the relays may be congured
as normally open or closed. The factory will ship the detectors with
the following settings.
1.) Fire relay (K2) – normally open:
-will close when there is a re continuously present beyond the
re time delay setting.
-will close when manual test is activated beyond the length of
time for the re delay time setting.
Note: The red light emitting diode (LED) will illuminate when
relay closes.
2.) Fault relay (K1) – normally open:
-will close within 8 seconds when power is applied.
-will open when power is lost or fuse F1(located on the PCB)
opens.
-will open when detector fails automatic test.
-will open when detector fails manual test.
-will open when switch 7 is on and no loop is present.
Note: The amber LED will be illuminated when relay opens,
unless there is a loss of power.
Note: Any adjustments to the user options listed above should
be done with the power“OFF”. The detectors will not recognize
any changes until the microprocessor is reset. Removing the
power allows a reset to occur.
Caution: Upon applying power, insure that the detector
remains on for at least 8 seconds to allow for complete
initialization to take place.
Fire Outputs Latching or Non-Latching
Switch position 6 selects the latching or non-latching Fire Outputs
option. To select latching, the switch position 6 must be toggled“ON”.
Upon detecting a re, the Fire Outputs signal will remain engaged as
long as power remains“ON” or until the detector is reset through the
RS485 User Interface (UI). If you select non-latching by toggling switch
position 6 to “OFF”, the Fire Outputs signal will disengage after a re is
extinguished.
Optical Self-Test
The Model 760 ame detector makes use of a self contained “through-
the-lens” optical clarity-checking feature. The factory setting is for
automatic test only, switch position 1 is“OFF”and switch position 2
is “ON”. (See Figure 6 for location of the switches and Figure 5 that
describe the switch settings for the user selectable interface.) If the
addition of the manual test feature is desired, then toggle switch
position 1 to “ON”. If only the manual test feature is needed, then
toggle the switch position 1“ON”and switch position 2 “OFF”. If no
optical testing is preferred then ensure that both of these switches are
“OFF”.
0 to 20 mA Output
Switch position 7 selects the 0 to 20 mA output option. If this output is
utilized, then switch position 7 must be“ON”. Otherwise, if this output
is not used, switch position 7 must be kept“OFF”or it will cause the
Fault Outputs to turn “ON”. Table 2 illustrates the order of priority.

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©Firey AB (Oktober 2016)
Table 2: Milliamp Logic Chart
Priority State Load Current mA
1 Fire 20 ± 0.2
2 Fire IR Warning 16 ± 0.2
3 Ref IR Warning 15 ± 0.2
4 Fire Relay Coil Fault 3 ± 0.2
5 Calibration not complete /
EEPROM Corrupted Fault
2 ± 0.2
6 Exceedance Fault 1.5 ± 0.2
7 Block Fault 2.5 ± 0.2
8 Self-Test Fault 1 ± 0.2
9 Current Loop Fault 0 ± 0.2
10 Normal 4 ± 0.2
RS485 MODBUS RTU
The Series 760 Flame Detector is equipped with a two wire, half-
duplex, serial communication interface which supports the MODBUS
RTU protocol. The RS485 MODBUS RTU will allow up to 31 detectors
to be networked to a controller (i.e., customized re panel or personal
computer). The network controller will perform the master duties.
Due to the network being in half-duplex mode, it will only allow one
transmitter to be broadcasting on the network at one time.
The RS485 MODBUS RTU Option
The RS485 MODBUS RTU is enabled when switch 8 is in the “ON”
position. The Flame Detector has to be programmed to a unique
detector number from 1 through 247. The detector number will give
the Flame Detector an address on the network.
Programming the Detector Address Number
This option is activated when switch position 9 is toggled“ON”. The
option is deactivated when the switch is in the “OFF”position. This
option provides the user with a method of programming the unit
number into the non-volatile memory of the microprocessor.
To program the detector address number, rst remove power from
the detector. Then toggle the program option“ON” and use the
remaining eight switches on the User Selectable Interface (USI) to set
the detector address number.
In program mode, the USI becomes a binary programmer as illustrated
in Table 3. When a switch is toggled“ON”, it will equal the binary
weighted number. These binary weighted numbers are added
together when a multiple number of switches are switched“ON” (i.e.,
if SW2 and SW3 were toggled“ON”, then the detector number would
equal a 6)
Table 3: Binary Weight for Switch States “ON”
SW1 SW2 SW3 SW4 SW5 SW6 SW7 SW8
1 2 4 8 16 32 64 128
When power is applied to the detector, the detector will sense that it is
in program mode and read the eight switch positions. From the switch
setting, it will determine the detector number. Once the number
has been determined, the detector will enter it into the non-volatile
memory of the microprocessor. Next, the amber LED will ash “ON”a
certain number of times equaling the detector address number in the
following manner: the detector will ash the hundreds digit, pause 2
seconds, ash the tens digit, pause 2 seconds, and then ash the ones
digit. Then it will hold the amber LED “ON”constantly for about 10
seconds. Next, the detector will repeat this sequence. This process will
continue for up to 5 minutes.
Once you are sure that the proper number is programmed, then shut
the power“OFF”and reset the USI options to suit your application.
Reference the section on the USI if you are not sure which option is
best for your application or call a Vibro-Meter, Inc application engineer.
Note: In the case that the program option switch is left“ON”and the
detector is installed on network, the detector will go through the same
process as explained previously, but after 5 minutes the detector will
reset and use the last USI setting that it had prior to going into the
program mode.
MODBUS RTU Protocol
A typical MODBUS message or Application Data Unit (ADU), which
is also referred to as a MODBUS RTU Message Frame, as illustrated in
Table 4 consists of a Slave Address byte, a Protocol Data Unit and two
CRC error checking bytes in accordance with the MODBUS standard.
A Slave Address of 0 is used when a message is directed to “ALL” Slave
Devices (MODBUS Broadcast Mode). A Slave address of 1 to 247 is
used when directing a message to a single Slave Device (MODBUS
Unicast Mode).
Table 4: MODBUS Application Data Unit Format
Slave Address Protocol Data Unit CRC Low CRC High
The Protocol Data Unit (PDU) shown in Table 5 consists of a function
code byte and a data eld. The data eld supported by this application
may be empty (no bytes) or it may contain up to two address and two
data bytes.
Table 5: MODBUS Protocol Data Unit Format
Function
Code
Address
High
Address
Low
Data
High
Data
Low
MODBUS RTU Supported Commands
In normal operating mode, the Flame Detector will receive and
respond to the following MODBUS commands listed in Table 6.
Table 6: PDU Supported MODBUS Commands
Supported Commands Function
codes
Addr
high
Addr
low
Data
high
Data
low
Fire & Fault relay status 0x01 0x00 0x00 0x00 0x08
USI Status 0x02 0x00 0x01 0x00 0x08
Fire Delay (EEPROM) 0x03 0x00 0x02 0x00 0x01
Warning Delay
(EEPROM)
0x03 0x00 0x03 0x00 0x01
Fire Occurrences 0x03 0x00 0x04 0x00 0x01
Fault Occurrences 0x03 0x00 0x05 0x00 0x01
Fire Delay (Measured) 0x03 0x00 0x06 0x00 0x01
Warning Delay
(Measured)
0x03 0x00 0x07 0x00 0x01
MODBUS ID# 0x06 0x00 0x08 0x00 0x00
to
0xFF
Clear Fire Occurrences 0x06 0x00 0x09 0x00 0x00
Clear Fault
Occurrences
0x06 0x00 0x0A 0x00 0x00
Software Reset 0x06 0x00 0x0C 0x00 0x06

10
©Firey AB (Oktober 2016)
MODBUS RTU Response
Based on the commands from Table 6, the read functions from the
Flame Detector are functions 1, 2, 3 and 7. In response to these
commands the Flame Detector will follow the PDU format illustrated
in Table 7. For function 6, the Flame Detector will simply echo the
received PDU to acknowledge that the specied command was
performed.
Note: The second PDU byte contains either the number of data bytes
that follow or, in the case of the Exception Status Word, Variable Data
as supplied by the main micro-controller.
Table 7: PDU Formats for Transmission of MODBUS Read Results
Read
Command
Function
Code
See
Note
Variable
Data
Variable
Data
Fire & Fault
relay status
0x 01 0x01 See Table
8
Not Used
USI Status 0x 02 0x01 See Table
9
Not Used
Fire Delay
(EEPROM)
0x 03 0x02 See Table
10
See Table
11
Warning Delay
(EEPROM)
0x 03 0x02 See Table
10
See Table
11
Fire
Occurrences
0x 03 0x02 Hi Byte Lo Byte
Fault
Occurrences
0x 03 0x02 Hi Byte Lo Byte
Fire Delay
(Measured)
0x 03 0x02 See Table
10
See Table
11
Warning Delay
(Measured)
0x03 0x02 See Table
10
See Table
11
Exception
Status Word
0x 07 See Table
12
Not Used Not Used
As illustrated in Table 8, if the relay is energized, the corresponding bit
will be set (1, high). If the relay is de-energized, the corresponding bit
will be cleared (0, low).
Table 8: MODBUS Function 0x01 Read Coil Response
Bit 7:2 Bit 1 Bit 0
Always 0 (Cleared) Fault Relay Status Fire Relay Status
As depicted in Table 9, if the option is active, the corresponding bit will
be set. If the option is not active, the corresponding bit will be cleared.
Table 9: USI Status Bit Denition
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3:2 Bit 1 Bit 0
RS-485
ENQ
0 to
20 mA
Output
Fire
Output
Latch-
ing
War-
ning
Indica-
tion
Sensiti-
vity
Manual
Test
Auto-
matic
Test
Table 10: Byte Denition for Delay Time Whole Number
Bit 7:4 Bit 3:0
BCD of 10’s digit BCD of 1’s digit
Table 11: Byte Denition for Delay Time Decimal
Bit 7:4 Bit 3:0
BCD of tenth’s digit Always cleared
Note: An example using Table 10 and 11; if the delay time is 25.3
seconds, the two bytes transmitted would be 0x25 and 0x30.
As shown in Table 12, the status word has seven alarm bits and one
valid transmission bit. When bits 0 through 6 are at a logic zero, the
alarms are “OFF”. When bits 0 through 6 are at a logic one, the alarms
are “ON”. Bit 7 is always“ON”. If bits 4 through 7 are set to logic one
then the relay coil is open. If bits 3 through 7 are set to logic one then
the non-volatile memory has been corrupted.
If the bits 1, 3 through 7 are all set to a logic one then the re channel
is in exceedance due to saturation either from excessive heating
or cooling. If bits 2, 3 through 7 are all set to a logic one, then the
reference channel is in exceedance due to saturation either from
excessive heating or cooling. If bits 1, 4 and 7 are all set to a logic one,
then the re window is being blocked or the sensor is producing an
illogical signal level as compared to the reference channel. If bits 2, 5
through 7 are set to a logic one, then the reference channel window
is being blocked or the sensor is producing an illogical signal level as
compared to the re channel.
Table 12: Status Word Denition
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Always
On
Manual
Test
Fault
Auto
Test
Ref IR
Fault
Auto
Test
Fire IR
Fault
Milli-
amp
Fault
Ref IR
Warn-
ing
Fire IR
Warn-
ing
Fire
MODBUS RTU Exception Handling
An exception is an error detected by the Flame Detector. If an error
should occur from the received command, the Flame Detector will
respond with a PDU in the form of Table 13.
Table 13: PDU Format for MODBUS Exception Reporting
Exception Function Code Exception Code
(0x80 + MODBUS Function Code) See Table 14
When assembling the PDU to annunciate an error, the Flame Detector
will calculate an Exception Function Code equal to 0x80 plus the
received MODBUS Function Code, i.e. if the MODBUS function was
0x03, the Exception Function Code is 0x83. Table 14 contains the
supported Exception Codes that will be returned depending on the
type of error detected.
Table 14: Supported Exception Codes
Exception Exception
Code
Reporting
Priority
Illegal function requested 0x01 1
Illegal address specied 0x02 2
Illegal data specied 0x03 3
Fire Detector Request
failure
0x04 4