Download megablock series

passive hubs for
fieldbus networks
MEGABLOCK SERIES
reliable interconnection for fieldbus networks
Megablocks are DIN rail mounted
passive hubs for Foundation Fieldbus
networks. They connect several field
devices to the network trunk cable and
provide short circuit and surge protection
to the segment. Megablocks minimize
hand wiring and allow individual devices
to be added to and removed from the
segment without disrupting network
communication.
A green power LED on each unit
indicates whether at least 9V of DC
power is present. Megablocks are
available in four and eight drop versions.
Multiple Megablocks are easily wired to
one another to allow larger segments to
be constructed.
The Megablock Terminator is easily
wired to any Megablock to prevent signal
reflection on the fieldbus segment. The
Megablock Terminator is clearly marked
for easy identification by field personnel.
The Megablock 8 and Megablock
Terminator are ideal for a star or
chickenfoot topology where several
transmitters are connected at a single
field junction box.
Occupying approximately the
same
junction
box
space
as
conventional
4-20
mA
wiring,
Megablocks are ideal for both retrofit
and greenfield installations.
Each Megablock has two dedicated
connections for the fieldbus home run
or trunk cable. Trunk connections are
easily identified by their black
connectors.
Separate
numbered
connections are provided for each spur
drop.
Connections to the Megablock
are made using pluggable screw
terminal type connectors. This allows
wire terminations to be made to the
individual connectors which are then
plugged into the Megablock. Devices
can then be easily connected and
disconnected during commissioning.
After commissioning, retaining screws
are tightened to secure each connector
to the Megablock.
To minimize susceptibility to
single points of failure, Megablocks
are available with built-in SpurGuard™
short circuit protectors which prevent a
short circuit in any of the individual
transmitters or spur cable runs from
bringing the entire fieldbus segment
down. A red LED near each spur
connection indicates that a spur is
shorted and is in overcurrent mode.
To protect field transmitters from
damage due to induced voltages on the
fieldbus cable, each Megablock has
built-in differential surge suppression
that is activated when the potential
across the twisted wire pair exceeds
39 VDC. The Megablock Terminator
has transient surge suppression that
works by shunting excess current to
ground when the shield to ground
potential exceeds 75 VDC.
Sect4c-1
SPECIFICATIONS
MTL - RELCOM
MEGABLOCKS
Megablock products will be approved for; Class I, Division 1 and 2
and Zone 1 and 2 applications.
For details see: www.relcominc.com/fieldbus
Mounting Requirements: 35 mm DIN rail
Wire Capacity: 12-24 AWG
Case material: Lexan Polycarbonate
Temperature Range: -45 to +70°C
Voltage Required to activate Power LED: 9.2V minimum
INSTALLATION
Megablocks can be mounted vertically or horizontally using 35 mm
DIN rail within a suitable enclosure, such as a field junction box.
Megablocks are removed from the DIN rail using a flat blade
screwdriver to release the mounting platform. Use of DIN rail end
stops is recommended to prevent sliding in vertical installations. Four
and eight port Megablocks have labeling areas so that segments can
be easily identified according to plant standards.
Megablocks with SpurGuards™
Power Consumption:
No SpurGuards™ tripped: 1.7 mA
per SpurGuard™ tripped: 60 mA
Maximum Current Delivered to Spur: 58.0 ± 1.0 mA
Trunk to Spur Voltage Drop (SpurGuard™ not tripped):
Maximum: 1.2 V
Typical: 0.4 V (17 mA device current draw)
Basic Megablocks
Power Consumption: 0.4 mA maximum
Maximum Current Delivered to Spur: Not Limited
Megablock Terminator
Operating Temperature Range: -45 to +70°C
Common Mode Voltage Limit: 39 V
Transient Mode Voltage Limit: 75 V
Shown above is an example of a common Fieldbus segment
topology. Eight field devices are connected to an eight-drop
Megablock, which is mounted in a field junction box. One trunk
connector on the Megablock is wired to a Megablock Terminator and
the other to the segment trunk cable that leads to the control room or
marshalling panel where the power supply and second terminator are
located. The Megablock Terminator in the field has a normally open
connection to earth ground that closes when surge conditions are
detected.
GROUNDING
To prevent ground loops, a fieldbus segment should only be grounded
at one point. This is usually done by grounding the cable shield at the
control room end of the segment. If a permanent segment ground
connection in the field is desired, this can be achieved by wiring the
shield terminal on one of the Megablock trunk connectors to a
suitable earth ground instead of wiring it to the shield terminal on the
Megablock Terminator.
ORDERING INFORMATION
Megablock Series
4-drop Megablock
Part Number
FCS-MB4
4-drop Megablock with integrated
SpurGuard™ short circuit protection
FCS-MB4-SG
8-drop Megablock
FCS-MB8
8-drop Megablock with integrated
SpurGuard™ short circuit protection
FCS-MB8-SG
Megablock Terminator
FCS-MBT
Accessories
Heavy Duty DIN rail end stop
35 mm DIN Rail, 1 metre length
Part Number
FCS-A06
FCS-A01
Sect4c-2
Physical Network
IEC61158-2
FOUNDATION™ Fieldbus H1
Profibus PA
connection system
for fieldbus
networks
FCS SERIES
reliable interconnection for Fieldbus networks
FOUNDATION™ Fieldbus H1 and
Profibus PA are digital communication
network protocols used in industrial
process control. Unlike traditional 4-20 mA
communications systems, fieldbus uses a
bus topology with multi-drop wiring. While
this offers opportunities for significant cost
savings relative to the point-to-point wiring
used in 4-20 mA systems, it also poses a
risk to control system reliability and
availability. Because transmitters on a
fieldbus network may share a single cable
run, a failure or short of any individual
device has the potential to interrupt data
communication across the entire bus
segment. Such events can occur due to
accidents or even during routine instrument
maintenance.
The Fieldbus Connection System
(FCS series) includes all the components
necessary to provide connection and
termination
of
field
devices
to
FOUNDATION™ Fieldbus H1 and Profibus
PA network segments. All FCS wiring
blocks have LED indicators for bus segment
power, expansion blocks to allow easy
expansion of the number of device
connections and circuitry to limit voltage
on the fieldbus wiring. The FCS blocks are
available with pluggable, screw terminal
or cage clamp connectors.
The Fieldbus Spur Block, FCS-S
series, provides four fieldbus cable
connections. For example, the Spur Block
can be used in the home run to attach two
devices to the middle of the Fieldbus.
Several Spur Blocks may be used on a
fieldbus segment. When adding spurs to a
fieldbus segment, the total maximum spur
length must not be exceeded as defined by
the IEC 61558-2 standard. Using a Spur
Block allows the removal of a device cable
from the fieldbus without affecting other
devices or the integrity of the segment
wiring
The grounded Terminating Block,
FCS-TG, is used as a terminator and
wiring block at the control room end of the
fieldbus. It interconnects up to four
shielded wire pairs. For example, the
home run cable, the DCS, the fieldbus
power supply, and one device. It contains
a high quality interconnection socket that
expands the number of devices which may
be attached to the control room end of the
segment (see Expansion Block). It provides
a connection from earth ground to the
shields of the fieldbus cables via the
ground stud. The shield should only be
grounded at one point on each segment to
prevent groundloop currents in the system.
The grounded Terminating Block is easily
identified by its black housing cover. Only
one grounded Terminating Block is used on
each fieldbus segment. The FCS-TG
requires the use of a separate fieldbus
power supply.
The isolated Terminating Block,
FCS-TI, is used as a terminator and wiring
block at the far end of the segment,
sometimes called the chicken foot. It
interconnects up to four shielded wire
pairs; for example, the home run cable
and three devices. It contains a high
quality interconnection socket that expands
the number of devices which may be
attached to the chicken foot (field) end of
the segment.
Surge suppressers are built into the
isolated Terminator to protect the devices
attached to the fieldbus from near lightning
strikes. A stainless steel ground stud is used
for earthing the induced surge currents.
When not discharging surges, the ground
stud is isolated from the shielding of the
Terminator and the wires as required by
the fieldbus standard and for intrinsic
safety considerations. Except for its grey
housing, it appears identical to the
grounded terminator.
The Expansion Blocks plug into either
a Terminator, a Spur Block, or into each
other so that wiring between blocks is
eliminated. As many Expansion Blocks as
needed may be used on a fieldbus
segment. The expansion connectors can
also be used for test equipment or handheld devices for temporary connection to
the fieldbus. The Expansion Block
eliminates inter-terminal block wiring or
having to put more than one wire into a
wire terminal.
FCS series wiring blocks can be
mounted vertically or horizontally within a
suitable enclosure, such as a field junction
box. They can be mounted directly or by
using 35 mm DIN rail. They are secured to
DIN rail by two extendable locking tabs.
DIN rail end stops are recommended to
prevent sliding in vertical installations.
Sect 4c-3
MTL - RELCOM
FIELDBUS TERMINATOR
FCS-T SERIES
DESCRIPTION
The Isolated Terminating Block, FCS-TI series, is used as a terminator
and wiring block at the far end of the segment, sometimes called the
chicken foot. It interconnects up to four shielded wire pairs. For
example, the home run cable and three devices. A high energy surge
suppressor built into the isolated Terminator protect the devices
attached to the fieldbus from near lightning strikes. A stainless steel
ground stud is used for earthing the surge currents induced into the
shields of the fieldbus wiring. When not discharging surges, the
ground stud is DC isolated from the cable shields. Except for its grey
housing, it appears identical to the grounded terminator. Only one
isolated Terminating Block is used on each fieldbus segment.
The Grounded Terminating Block, FCS-TG series, is used as a
terminator and wiring block at the control room end of the fieldbus.
The Terminator interconnects up to four shielded wire pairs. For
example, the home run cable, a DCS, a fieldbus power supply, and
one device. It provides a connection from earth ground to the shields
of the fieldbus cables via the ground stud. The shield should only be
grounded at one point on each segment to prevent groundloop
currents in the system. The grounded Terminating Block is easily
identified by its black housing cover. Only one grounded Terminating
Block is used on each fieldbus segment.
Both Terminators have a built-in differential surge suppressor that
limits spikes which may be present on the fieldbus. This protects
attached devices from damage. The Terminators can also be
expanded with Relcom Fieldbus Expander blocks, FCS-E series, to
provide four additional device connections. The Terminators have an
LED that illuminates to indicate when segment power is present.
APPLICATION
Fieldbus devices are connected to the Terminator with shielded
twisted pair fieldbus cable. Up to four connections may be made at
the Terminator. The connections are typically one homerun cable and
one, two, or three device cables. A controller or DCS is considered
to be a "device". To prevent "ground loop currents" only one point
on each segment should be grounded. If a Grounded Terminator and
an MTL Power Conditioner are used on the same segment, only one
of them should be grounded. The bolt on the Isolated Terminator
should ALWAYS be grounded. The Terminator may be mounted on a
flat surface with screws or on a 35mm DIN rail using the integrated
sliding tab. See the package outline for additional mounting and
dimensional details.
SPECIFICATIONS
All FCS-TI and FCS-TG Series:
Terminator:
100 ohm 1%, 1 µF 50 V
Operating Temperature:
-45 C to +70 C
LED Current:
3 mA maximum
(at 32 Volt segment power)
Expansion connector:
One set female (gold plated)
Wire Capacity:
12-24 AWG
Case material:
ABS plastic
Weight:
105 g
FCS-TI-PL, FCS-TI-ST, and FCS-TI-CC:
Surge Limit Start:
39 Volts (differential)
Surge Limit (Hard):
43 Volts (differential)
Surge Capacity:
10,000 ampere µs (lightning)
Sect 4c-4
FCS-TG
Fieldbus
Power Supply
HOST
O +
G S
B O +
G S
B -
+
S
+
S
-
O
G
B
O
G
B
Grounded
Terminator Block
Device 2
O +
G S
B O +
G S
B -
FCS-S
+
S
+
S
-
O
G
B
O
G
B
+
S
+
S
-
O
G
B
O
G
B
Device 1
Homerun
Device 3
Spur Block
Homerun
FCS-TI
Device 6
O +
G S
B O +
G S
B -
Device 4
Device 5
Isolated
Terminator Block
SAMPLE TOPOLOGY
The topology above illustrates a fieldbus segment. If additional
fieldbus devices need to be added, Expansion Blocks (FCS-E) can be
plugged into any of the FCS wiring blocks to increase the number of
fieldbus connection points by four (4) for each Expansion Block used.
The shields of the segment wiring are grounded by attaching the bolt
on the Grounded Terminator to ground. Grounding the bolt on the
Isolated Terminator Block provides protection from shield currents
induced by near lightning strikes but does not provide a connection
to ground under normal operating conditions.
MTL - RELCOM
FIELDBUS EXPANDER
FCS-E SERIES
DESCRIPTION
Fieldbus Connection System blocks can be expanded for additional
wire pair connections by using the Expander Block, FCS-E. Each
Expander Block provides four more cable connection points. The
Expander Block plugs into a Terminator, Spur Block or into another
Expander block so that wiring between blocks is eliminated. As many
Expander Blocks as needed can be used on a fieldbus segment. The
Expander Block has an LED which illuminates to indicate bus power
is present.
FCS-TG
HOST
FCS-TI
The Expander Block simply plugs into other Relcom wiring blocks and
into other Expander blocks. All Relcom fieldbus blocks may be
mounted with screws to a flat surface or snapped onto a 35mm DIN
rail. See Package Outline for dimensions and mounting information.
If the Expander Block is to be mounted on a DIN rail, an end stop,
FCS-A02, should be used to prevent separation of the plugged
modules.
SPECIFICATIONS
Wire Capacity:
Case material:
Weight:
Device 2
Device 3
O
G
B
O
G
B
Isolated
Terminator Block
O +
+O
G S
S G
- B
B O +
+O
G S
S G
- B
B O +
G S
B O +
G S
B -
Device 5
Device 8
FCS-E
-45 to +70°C
3 mA max. at 32 VDC
39 Volts
43 Volts
One set female One set male
(gold plated)
12-24 AWG
ABS plastic
95 g
+
S
+
S
-
Grounded
Terminator Block
APPLICATION
Temperature Range:
LED Current:
Surge Limit Start:
Surge Limit (Hard):
Expansion connectors:
O +
G S
B O +
G S
B -
Fieldbus
Power Supply
+
S
+
S
-
O
G
B
O
G
B
Device 1
Homerun
Device 4
Device 6
Device 7
Expansion Block
SAMPLE TOPOLOGY
In the example above, the power supply and one terminator are
located at one end of the segment (usually near the control room). The
home run or trunk cable runs into the field and connects to a field
junction box. There, the home run cable is connected to a wiring
block (FCS-T series) that contains the second terminator for the
segment. This configuration alone would allow for connection of three
device spurs. With the addition of one Expander block (FCS-E series)
the number of device spurs available on the segment is increased to
seven. Two expander blocks would bring the total to 11 devices.
Sect 4c-5
MTL - RELCOM
FIELDBUS SPUR BLOCK
FCS-S SERIES
DESCRIPTION
The Fieldbus Spur Block, FCS-S series, provides four fieldbus cable
connections. For example, the Spur Block can be used in the home
run to attach two devices to the middle of the fieldbus. Several Spur
Blocks may be used on a fieldbus segment. When adding spurs to a
fieldbus segment, the total maximum spur length must not be
exceeded as defined by the ISA SP50.02 standard. Using a Spur
Block allows the removal of a device cable from the fieldbus without
affecting other devices or the integrity of the segment wiring. The Spur
Block can also be expanded with the Relcom Fieldbus Expander
Block to provide four additional device connections. The Spur Block
has an LED that illuminates to indicate when segment power is
present. A built-in differential surge suppressor limits spikes that may
be present on the fieldbus and protects attached devices from
damage. Spur Blocks are available with pluggable (FCS-S-PL), screw
terminal (FCS-S-ST), or cage clamp connectors (FCS-S-CC).
FCS-TG
O +
G S
B O +
G S
B -
Fieldbus
Power Supply
HOST
O
G
B
O
G
B
Grounded
Terminator Block
O +
G S
B O +
G S
B -
Device 2
FCS-S
+
S
+
S
-
O
G
B
O
G
B
+
S
+
S
-
O
G
B
O
G
B
Device 1
Homerun
Device 3
Spur Block
Homerun
FCS-S
APPLICATION
Fieldbus devices are connected to the Spur Block with shielded
twisted pair fieldbus cable. Up to four connections may be made at
the Spur Block. The connections are typically two homerun cables
and one or two device cables. The Spur Block may be mounted on a
flat surface with screws or on a 35mm DIN rail using the integrated
sliding tabs. See the package outline on the next page for additional
mounting and dimensional details.
O +
G S
B O +
G S
B -
Device 5
-45 to +70°C
3 mA max. at 32 VDC
39 Volts
43 Volts
One set female (gold plated)
12-24 AWG
ABS plastic
95 g
Device 4
Spur Block
FCS-TI
Device 6
SPECIFICATIONS
Temperature Range:
LED Current:
Surge Limit Start:
Surge Limit (Hard):
Expansion connector:
Wire Capacity:
Case material:
Weight:
+
S
+
S
-
Device 7
Isolated
Terminator Block
O +
+O
G S
S G
- B
B O +
+O
G S
S G
- B
B O +
G S
B O +
G S
B -
Device 9
Device 11
FCS-E
+
S
+
S
-
O
G
B
O
G
B
Homerun
Device 8
Device 10
Device 12
Expansion Block
SAMPLE TOPOLOGY
The topology shown above uses a power supply at the control room
end of the fieldbus segment. If fieldbus devices need to be in or near
the control room, an Expander Block can be plugged into the
terminator wiring block to expand the number of fieldbus connection
points by four (4). The shields of the segment wiring are grounded by
attaching the ground bolt on the grounded terminator block to
ground. Grounding the bolt on the Isolated Terminator Block provides
protection from shield currents induced by near lightning strikes but
does not provide a connection to ground under normal operating
conditions.
Sect 4c-6
MTL - RELCOM
ORDERING INFORMATION
FCS SERIES
FCS PACKAGE OUTLINE
(Ground/surge connection bolt and Male expansion connector not
shown)
79.4 mm, 3.125"
1 S
S 2
35 mm, 1.4"
FCS-T Series
Terminator Block with surge
suppression and cage clamp connectors
Part Number
FCS-TI-CC
3 S
Terminator Block with surge
suppression and pluggable screw terminal
connectors (SpurGuard™ compatible)
FCS-TI-PL
92 mm, 3.6"
Terminator Block with surge
suppression and screw terminal
connectors
FCS-TI-ST
Terminator Block with permanent
connection of cable shield to ground
and cage clamp connectors
FCS-TG-CC
Terminator Block with permanent
connection of cable shield to ground
and pluggable screw terminal
connectors (SpurGuard™ compatible)
FCS-TG-PL
Terminator Block with permanent
connection of cable shield to ground
and screw terminal connectors
FCS-TG-ST
FCS-S Series
Spur Block with cage clamp
type connectors
Part Number
FCS-S-CC
Spur Block with pluggable
screw terminal connectors
(SpurGuard™ compatible)
FCS-S-PL
Spur Block with screw terminal
connectors
FCS-S-ST
FCS-E Series
Expander Block with cage clamp
connectors
Part Number
FCS-E-CC
Expander Block with pluggable
screw terminal connectors
(SpurGuard™ compatible)
FCS-E-PL
Expander Block with screw terminal
connectors
FCS-E-ST
Accessories
35 mm DIN Rail, 1 metre length
DIN rail end stop
Part Number
FCS-A01
FCS-A02
S 4
5 mm, 0.2"
Dia.
34 mm, 1.34"
35 mm
35 mm DIN Rail
Mounting tabs expanded
Sect 4c-7
overcurrent
protection for
fieldbus networks
SPURGUARD™ SERIES
cost effective interconnects for fieldbus networks
◆ 20 and 40mA versions
◆ overcurrent protection
◆ US patent pending
◆ standard DIN rail mount
Sect 4c-8
FOUNDATION™ FieldbusH1 and
Profibus PA are digital communication
network protocosl used in industrial process
control. Unlike traditional 4-20 mA
communications systems, fieldbus uses a bus
topology with multi-drop wiring. While this
offers opportunities for significant cost
savings relative to the point-to-point wiring
used in 4-20 mA systems, it also poses a risk
to control system reliability and availability.
Because transmitters on a fieldbus network
may share a single cable run, a failure or
short of any individual device has the
potential to interrupt data communication
across the entire bus segment. Such events
can occur due to accidents or even during
routine instrument maintenance.
A SpurGuard™ is a current-limiting
device that provides short circuit protection
to the fieldbus segment. By attaching a
SpurGuard™ at each point where a field
transmitter attaches to the segment home run
cable, isolation of the network from
individual device failures is achieved. A red
LED indicates when a SpurGuard™ is
providing
overcurrent
protection.
SpurGuards™ are part of the Relcom
Fieldbus Connection System (FCS-series) and
are intended to work with any DIN rail
mounted FCS wiring block that uses
removable (pluggable) connectors.
SpurGuards™ are available in current
ratings of 20 and 40mA (plus ~ 30 mA
safety buffer) to match the requirements of
specific field transmitters.
MTL-RELCOM
SPURGUARDTM
SPURGUARD™ SELECTION
Because SpurGuards™ draw power from the segment when in short
circuit mode, their short circuit current consumption must be taken into
account during segment design. Use of SpurGuards™ with the lowest
possible current consumption is recommended. This prevents
excessive power from being drawn from the segment under short
circuit conditions.
To determine the SpurGuard™ for your application, add the nominal
current requirement of the field device connected to the spur, 10mA
of signaling current, and overhead to allow for temperature variations
and the possible attachment of bus-powered test equipment to the
spur. If the total current requirement is 50mA or less, the FCS-SG-20
is recommended.
INSTALLATION
SpurGuards™ are connected at each point where a spur attaches to
the segment trunk. This is done by connecting the twisted pair cable
that leads to the field transmitter to the SpurGuard™ which is then
plugged into a Relcom FCS wiring block attached to the trunk.
SPECIFICATIONS
Short Circuit Current Limit*
-40°C
20°C
50°C
FCS-SG-20
60mA
52mA
47mA
FCS-SG-40
91mA
78mA
71mA
*The current limit decreases under prolonged short circuit conditions
due to heating of SpurGuards™.
Voltage Drop
Trunk to Spur (SpurGuard™ not tripped):
Maximum: 0.9 V
Typical: 0.2 V (17 mA device current draw)
Temperature Range:
Wire Capacity:
Case material:
Weight:
Dimensions:
-40 to +70°C (ambient still air)
12-24 AWG
Lexan Polycarbonate
9g
15.2 × 13.7 × 29.2 mm
0.600"
15.2mm
0.540"
13.7mm
+ S –
MOUNTING REQUIREMENTS
SpurGuards™ require the use of Relcom FCS wiring blocks with
pluggable connectors: FCS-S-PL, FCS-E-PL, FCS-TI-PL, or FCS-TG-PL.
FCS wiring blocks are installed within a suitable enclosure, such as a
field junction box, and are mounted using 35mm DIN rail. Flat panel
installation is possible using the provided mounting screw holes.
Voltage Limitations (at 70°C ambient still air)
To prevent overheating under prolonged short circuit conditions,
observe the following voltage* limitations:
FCS-SG-20
31.0 VDC
FCS-SG-40
19.5 VDC
*The voltage present at a SpurGuard™ is a function of the power
supplied to the segment, the load on the segment, and the length of
cable separating the power supply from each SpurGuard™. See the
Relcom Fieldbus Wiring Design and Installation Guide for detailed
instructions on calculating power distribution on a Fieldbus segment.
WARNING: Under prolonged short circuit conditions,
SpurGuards™ may achieve surface temperatures in excess of 100°C.
Use appropriate personal protective equipment when handling a
SpurGuard™ that is, or has recently been, in short circuit mode. Short
circuit mode is indicated by the red LED on each SpurGuard™.
0.860"
21.8mm
1.150"
29.2mm
ORDERING INFORMATION
SpurGuard™
FCS-SG-20
FCS-SG-40
Wiring Block
FCS-S-PL
FCS-E-PL
FCS-TI-PL
FCS-TG-PL
Description
SpurGuard™ for 20mA field devices
(short circuit current limit = ??mA)
SpurGuard™ for 40mA field devices
(short circuit current limit = ??mA)
Description
Fieldbus Spur Block with pluggable connectors
Fieldbus Expander Block with pluggable
connectors
Fieldbus Terminator with surge suppression and
pluggable connectors
Fieldbus Terminator with permanent cable shield
to ground connection and pluggable connectors
Sect 4c-9
live troubleshooting
for FOUNDATION™
Fieldbus H1
networks
The Fieldbus Monitor, FBT-3 is used to
examine the operation of a live
FOUNDATION™ Fieldbus network without
interfering with its operation. The monitor is
intended for maintenance personnel to verify
network operation or to troubleshoot an
errant network. The Fieldbus Monitor allows
the user to quickly assess the health of a
fieldbus network segment by providing
measurements of bus power level, minimum
signal level, and peak and average noise
level. It also displays the number of devices
present on the segment and indicates when
devices are added or removed from the
network.
The Fieldbus Monitor is palm-sized for
portability and is powered by the fieldbus so
that no batteries or external power source is
required. It includes color-coded test leads
and an LCD display.
Operation
The FBT-3 can be connected to the network
using the clip leads. The test leads are
polarity sensitive and the Monitor will not
operate if they are reversed. When first
connected to a fieldbus, a Version number is
displayed for 1 second. The MODE button is
used to select from several network
parameters that can be examined with the
Monitor. When a function is selected, the
LCD display reads “- - -” until the monitor has
collected and processed the data. After that,
the measured value is shown. The indication
“OK” is shown if the measured value is
within the acceptable range (as defined by
the fieldbus specification). The rotating
symbol in the lower right corner of the
display indicates that there is network
Sect 4c-10
FBT-3
FOUNDATION™ Fieldbus monitor
activity. A horizontal bar under the rotating
symbol indicates that a frame was detected,
but could not be decoded. This is not a
maintained function. I.e., if a single “bad”
frame is detected, the horizontal underbar
will only be on the display for a short time.
Periodic “bad” frames will cause the
underbar to blink. Following are more
detailed explanations of each of the
monitor’s modes:
Power
The DC voltage on the network is shown.
Measurements over 9 volts are OK. The
maximum displayed value is 25.5 volts.
LAS
If there is any activity on the network, the
Link Active Scheduler (LAS) should be
sending out Probe Node frames. The
Monitor measures the signal level of the
Probe Node frame. The signal level is in
millivolts.
Device
If there are fieldbus devices active on the
network, the Monitor counts them. If the
count has remained the same since the
Device function was selected, the display
shows “OK”. Note that the LAS is
considered a device and as such is included
in the count. Devices are counted by
watching their response to a Pass Token. If a
device does not respond to the Pass Token, it
is taken off an internal list and the count will
be reduced. The device may still show up on
PC monitoring software because the LAS will
not take it off of the Live List until it has failed
to respond to a Pass Token three times in a
row.
If a device leaves the network, “-” is
displayed. If a new device is added, the
display shows “+”
Low
The signal level of the device with the
weakest signal is shown. The device’s
address (hexadecimal) is displayed behind
the word "LOW". This will be the lowest
signal level reading from a device since the
tester was connected to the fieldbus.
Measurements greater than 150 mV are OK.
Noise Av
The noise on the network is measured during
the silence between frames. The value is
averaged
over
10
measurements.
Measurements of less than 75 mV are OK.
Noise Pk
The peak noise recorded since this function
was started is displayed. Measurements of
less than 75 mV are OK.
New
If a new device is to be added to the
network, it must respond to the Probe Node
frame sent by the LAS. The Monitor measures
the signal level of the new device’s response.
Measurements greater than 150 mV are OK.
The address (in hexadecimal) of the new
device is displayed also.
Specifications
The Monitor is powered by the fieldbus and
draws approximately 10 mA of current from
the network (depending on bus voltage and
ambient temperature). The Monitor carries
the CE mark and may be used in hazardous
areas.
Operating temperature range: 0-50ºC
Dimensions: 12.9 × 7.0 × 3.1 cm
Weight: 150 g
monitoring of
FOUNDATION™
Fieldbus networks
FBT-4
fieldbus power and signal monitor
The Fieldbus Power & Signal Probe,
FBT-4, is used to examine the operation of
a live FOUNDATION™ Fieldbus network
without interfering with its operation. The
Probe is intended for maintenance personnel
to verify network operation or to
troubleshoot an errant network. The Power
and Signal Probe is designed to help
instrument technicians quickly determine if
bus power and signal levels are within
specification at individual points on a
fieldbus network segment. For example, if a
fieldbus transmitter suddenly goes off-line,
the FBT-4 can be used to determine if the
problem resides in the transmitter itself or is
due to an open or short in the network cable
system. Inexpensive and portable, the FBT-4
runs on bus power and thus requires no
batteries or other external source of power.
Operation
Connection
One red and two green LEDs indicate the
status of the fieldbus network. They are
labeled Signal, Voltage, and Reversed. A lit
green LED indicates that the network is
performing satisfactorily. A lit red LED
signals an error condition. Following are
descriptions of the three indicators:
Signal indicates that there is bus activity. It
will only light if data traffic is detected with
peak to peak amplitude greater than 150
millivolts. The validity of the data is not
checked. You will notice that the LED blinks
when there is bus activity. It is driven directly
by the frame data and is thus not powered
during the brief silence between packets.
Voltage indicates that the DC Voltage on
the fieldbus is greater than the 9.0 VDC
minimum that is required by the fieldbus
standard.
Reversed indicates that the FBT-4 probes
have been connected to the network
incorrectly or that the fieldbus has been
wired with reversed polarity.
The pointed probe attached directly to the
case of the FBT-4 is the negative input and
should be connected to a negative point on
the fieldbus. The red wire with the pointed
probe should be connected at a positive
point on the fieldbus. For hands-free
operation, a red mini-hook assembly is
available which can be attached to the end
of the red pointed probe. A black cable with
mini-hook is also available to plug onto the
negative terminal of the FBT-4.
Specifications
The Monitor is powered by the fieldbus and
draws 12-15 mA of current, depending on
bus voltage and ambient temperature. The
Monitor may be used in hazardous areas.
Operating temperature range: 0-50ºC
Weight: 300g
Size: 11.8 × 5.0 × 2.1 cm
Sect 4c-11
accurate
characterization
of fieldbus
wiring
FBT-5
fieldbus wiring validator
The Fieldbus Wiring Validator, FBT-5,
is used in combination with the Relcom
Fieldbus Monitor, FBT-3, to test new or
existing field wiring to determine its
suitability for use in a FOUNDATION™
Fieldbus network. The FBT-5 acts as a signal
generator, supplying DC power and a
simulated fieldbus signal to the wire pair
being tested. The FBT-3 is then used to take
power, signal, and noise measurements.
Testing can be performed on existing
instrumentation wiring, multi-pair cables,
newly installed fieldbus cable, or a complete
fieldbus wiring system with wiring blocks
and terminators already installed.
Connection
Using the clip leads, connect the FBT-5 to
one end of the cable. To the other end,
attach the Test Terminator. Connect the FBT-3
to the Test Terminator. Be sure to attach the
red clips to the positive fieldbus wires and
the black clips to the negative. If the wires
are reversed, the Monitor will not function.
FBT-5
T
Cable to be tested
FBT-3
Operation
The Wiring Validator has a push-button
Power switch to turn it on or off. If the Wiring
Validator is turned on with a single click of
the Power button, it will stay on for about 5
minutes and then automatically turn itself off
to conserve battery power. If the Wiring
Validator needs to be powered on
indefinitely, such as when wire testing is
being performed by a single person, press
and hold the Power button for about 3
Sect 4c-12
seconds. The green Power On light shows
that the Wiring Validator is on.
• If the Power On light blinks rapidly (about
three times per second), the Wiring Validator
or Fieldbus Monitor is not attached to the
wire pair or the connection is reversed.
• If the Power On blinks slowly (about once
a second), there is a good connection to the
wire pair and Fieldbus Monitor, and the
Wiring Validator is in battery save mode
(and will automatically power down in about
five minutes).
• If the Power On indicator lights
continuously, all connections have been
made properly and the Wiring Validator will
stay on until it is manually powered off.
When the Wiring Validator is turned on, the
Fieldbus Monitor powers up and displays the
following readings:
• Voltage should be between 9 and 10 Volts
• Push the Monitor's Mode button once to
get the LAS function. The LAS signal level
reading should say "OK" and show the
signal level in millivolts:
LAS Signal (mV) Wire Condition
350 or more
Excellent
200-350
Good
150-200
Marginal
150 or less
Not Good
• Push the Monitor's Mode button three
times to get the NOISE AVerage reading. It
should say "OK" and display the average
noise level:
Noise Level (mV) Wire Condition
25 or less
Excellent
25-50
Good
50-75
Marginal
75 or more
Not Good
Wire System Testing
A complete fieldbus wire system, with two
terminators and other wiring blocks
installed, can be tested before field devices
are connected. This is done in the same way
as the wire testing described previously
except that the Test Terminator is not used.
Note: The wiring system cannot have
fieldbus devices attached to it during testing.
The Wiring Validator is not capable of
providing power to the fieldbus devices and
its signal generator will interfere with any
data transmission that the fieldbus devices
attempt to initiate.
If the wiring system has two terminators
installed (as required for proper fieldbus
operation), test results will be comparable to
the results of the wire by itself. However, if
too few or too many terminators have been
installed, the measured signal levels will be
inaccurate. The chart below shows the
relative values of LAS signal level that will be
observed:
Terminators
LAS Signal (mV)
0
999
1
961
2
(correct number) 760
3
637
Error Conditions
A blinking Low Battery light indicates that the outputs of the Wiring
Validator are shorted. The Low Battery light may also flash briefly as
the Wiring Validator is first attached to a wire pair. A continuously lit
Low Battery light indicates that the batteries need to be replaced.
Self Test
To verify that the Wiring Validator and the Fieldbus Monitor are
working correctly, connect them to each other through the Test
Terminator. Observe the power, signal, and noise values and verify
that they are within the following ranges:
Measurement
Acceptable Range
Power
9 to 10 Volts
LAS Signal
700 to 800 mV
Noise AVerage
less than 25 mV
If the observed values fall outside of these ranges, replace the
batteries as described below. If the problem persists, contact Relcom
for assistance. The unit contains no user serviceable parts.
Additional Wiring Tests
To get a complete characterization of the fieldbus wiring, measure the
resistance between the individual conductors in the cable using a
standard ohmmeter.
Suggested measurements include:
• The resistance between the twisted-pair wires
• The resistance between each of the twisted pair wires
and the shield/drain (if present)
• The resistance between the shield/drain and instrument
ground bar.
Readings of 100K ohms or higher are acceptable.
Additional System Requirements
A Relcom Fieldbus Monitor, FBT-3, is required to obtain signal and
noise measurements as described in these instructions.
1.22"
31 mm
Fieldbus
Wiring Validator
Power
On
Low
Battery
FBT-5
5.08"
129 mm
Power
2.75"
69.9 mm
ORDERING INFORMATION
Description
Fieldbus Wiring Validator
Fieldbus Monitor
Part Number
FBT-5
FBT-3
Batteries
The Wiring Validator uses four replaceable AA alkaline batteries.
Under continuous use, the Wiring Validator's batteries last about 12
hours. To replace the batteries, remove the four screws on the back of
the Wiring Validator to release the cover.
Specifications
The FBT-5 includes batteries, soft case, Test Terminator, clip leads, and
operating instructions.
Operating temperature range: 0 to 50°C
Dimensions: 12.9 × 7.0 × 3.1 cm (5.1 × 2.8 × 1.2”)
Weight: 600 g
Caution
The Wiring Validator must not be used in hazardous
areas or to power wiring that runs into hazardous areas.
Sect 4c-13
NOTES
Sect 4c-14