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FieldPoint Operating Instructions
FP-TB-1/2/3
FieldPoint Terminal Bases
These operating instructions describe the installation, features,
and characteristics of the FP-TB-1, FP-TB-2, and FP-TB-3.
Features
The FP-TB-1, FP-TB-2, and FP-TB-3 are FieldPoint terminal
bases with the following features:
•Works with all FieldPoint I/O modules (the FP-TB-3 is
designed specifically to work with thermocouple I/O modules)
•V andC terminals provideexternal supply voltages common to
all channels
•DIN-rail mounting or panel mounting
•32 terminals available for field connections (FP-TB-3 has 16)
•Available with screw terminals (FP-TB-1 and FP-TB-3) or
spring terminals (FP-TB-2)
•Isothermal construction (FP-TB-3) minimizes temperature
gradients when using thermocouples
•–40 to 70 °C operation
The FP-TB-1, FP-TB-2, and FP-TB-3 terminal bases provide the
intra-system communication link between FieldPoint I/O modules
and network modules, provide a means for wiring field
connections, and provide the mounting mechanism. You can
choose your terminal base depending on the type of field wiring
terminal you prefer: screw terminal or spring terminal.
FieldPoint™, National Instruments™, NI™, and ni.com™ aretrademarks of National Instruments Corporation.
Product and company names mentioned herein are trademarks or trade names of their respective companies.
For patents coveringNational Instrumentsproducts, refer tothe appropriate location:
To avoid damaging the network module and
terminal base, make sure that power is not applied to the
network module while you are installing or removing a
terminal base.
FieldPoint terminal bases have simple rail clips for reliable
mounting on a standard 35 mm DIN rail. Follow these steps to
mount the terminal base on a DIN rail.
1. Write down the serial number, located on the back of the
terminal base, before you mount it on the DIN rail.
2. Use a flathead screwdriver to open the DIN rail clip to the
unlocked position, as shown in Figure 1.
12
1 Rail clip locked2 Rail clip unlocked
Figure 1. Unlocking the Rail Clip
3. Attach the lip on the rear of the terminal base onto the top of a
35 mm DIN rail and press it down onto the DIN rail, as shown
in Figure 2.
Figure 2. Attaching the Terminal Base to a DIN Rail
4. Slide the terminal base along the DIN rail until its local bus
connector mates with the connector of the terminal base or
network module adjacent to it.
5. After the terminal base is in position, lock it to the DIN rail by
pushing the rail clip to the locked position.
6. To add more terminal bases, install them on the rail and
connect their local bus connectors together.
7. Place the protective cover onto the local bus connector of the
last terminal base on the bank, as shown in Figure 3. Add rail
locks by sliding them on and tightening the screws.
Figure 3. Adding Rail Locks and Protective Cover
Mounting the FP-TB-1/2/3 to a Panel
Caution
To avoid damaging the network module and
terminal base, make sure that power is not applied to the
network module while you are installing or removing a
terminal base.
Follow these steps to mount the terminal base on a wall or panel.
1. Use Figure 4 to locate where to drill the mounting holes on the
panel. Dimensions are given in millimeters [inches].
Refer to Figure 6 and follow these steps to install an I/O module on
the terminal base.
1. Slide the terminal base key to the appropriate position for the
I/O module. The position marked X is a universal position that
works for all modules.
2. Align the alignment slots on the I/O module with the guide
rails on the terminal base.
Key
Latch
Alignment
Slot
Guide Rails
Terminal BaseI/O Module
Figure 6. Mounting the I/O Module on the Terminal Base
3. Press firmly to seat the I/O module on the terminal base. When
the module is firmly seated, the terminalbase latch locks it into
place and the ejector button on the top of the terminal base
pops up.
4. To remove an I/O module, press the ejector button on top of the
terminal base and pull off the module.
The FP-TB-1 and FP-TB-2 provide four dedicated terminals and
32 numbered terminals defined by the I/O module. The terminals
are designed for 16–26 AWG copper conductor wire with 7 mm
(0.28 in.) of insulation stripped from the end as shown in Figure 7.
Use only copper wire unless you are working with a sensing
device, such as a thermocouple, that requires a different kind
of wire.
7mm
Figure 7. Conductor Wire with the Correct Strip Length
The four dedicated terminals are two V and two C terminals, one
of each at both ends of the terminal base. The two V terminals
are internally connected by the terminal base, as are the two
C terminals. Generally, these terminals are intended to connect
external power supplies to field devices. FieldPoint I/O modules
get their power from the network module through the backplane,
and in most cases require no external power for proper operation.
Refer to the appropriate I/O module operating instructions
for details on the use of these terminals and the other 32 terminals.
The FP-TB-3 provides two dedicatedC terminals and 16 numbered
terminals defined by the I/O module. Although the FP-TB-3 is
designed specifically to work with thermocouple modules, I/O
modules that do not require external power and that only use
terminals 1 to 16 can be used with the FP-TB-3.
Caution
make sure that power is not applied to it.
Before you connect wires to the terminal base,
Connecting Wires to the FP-TB-1 or FP-TB-3
Follow these steps to connect wires to the FP-TB-1 or FP-TB-3.
1. Loosen the terminal screw you want to wire.
2. Insert the wire in the terminal.
3. Tighten the screw terminal to 0.5–0.6 N ⋅ m (4.4–5.3 lb ⋅ in.) of
torque.
Follow these steps to connect wires to the FP-TB-2.
1. Insert a screwdriver into the slot directly below the terminal
number and push the screwdriver downward into the slot. You
may need to push hard. This forces the spring-loaded terminal
to open.
2. Insert the wire in the terminal.
3. Withdraw the screwdriver, allowing the spring terminal to
clamp securely onto the wire.
V12345678910111213141516V
C17181920212223242526272829303132C
Figure 8. Connecting Wires to the Spring Terminals of the FP-TB-2
Consider the following points when connecting power to the
FieldPoint system.
•The total current flowing through the V and C terminals must
be limited to 10 A. If you have a single external supply for the
field devices of more than one module, wire the supply to the
V and C terminals as shown in Figure 9.
1
2
1 When total current draw is
less than 10 A
Figure 9. Connecting Power for Current Draws Below and Above 10 A
Caution
Cascading power from neighboring bases or
2 When total current draw is
greater than 10 A
network modules defeats isolation between cascaded
modules.
•When total current draw is less than 3 A, you can use a single
terminal for the return path. If the total current draw is greater
than 3 A, you should use separate C terminals, as shown in
Figure 10.
Figure 10. Connecting Power for Current Draws Below and Above 3 A
•You need to wire power to the terminal bases only if you want
to use the terminal bases to route power to field devices or if
the I/O module requires it. FieldPoint I/O modules get their
power from the network module through the backplane and,
in most cases, require no external power for proper operation.
Refer to your I/O module operating instructions for details. In
Figure 11, shades of gray indicate differing voltage potentials.
FP-TC-120FP-AO-200FP-AI-110
Figure 11. Different Voltage Potentials
Caution
Cascading power from neighboring bases or
Live (V)
Ground
Neutral (C)
FP-RLY-420
network modules defeats isolation between cascaded
modules.
•You may want to use separate power supplies for I/O modules
both to prevent power dips caused by field devices from
disrupting the operation of the networkmodule and tomaintain
the isolation barrier between the I/O modules and the network
module. Figure 12 shows an example configuration with both
separate power supplies and cascading power.
FP-TC-120FP-RLY-420FP-AO-200FP-AI-110
1
2
Thermocouple
(self powered)
17
V
sup
4-20 mA
Figure 12. Example Power Supply Configuration for a FieldPoint Bank
V
COM
IN
2
I
IN
–+
±5V
118 Common
Channel 0
2
18
Caution
Cascading power from neighboring bases or
network modules defeats isolation between cascaded
modules.
Thermocouple Wiring
The FP-TC-120 thermocouple input module has the ability to
measure the temperature of the terminals on any of the FieldPoint
terminal bases. This measurement is called the cold junction
temperature and indicates the temperature of the junctions
between your thermocouple wire and the screw terminals. This
measurement is used internally by the FP-TC-120 to correct for
the thermoelectric voltages that are generated at these junctions.
Heat dissipated by adjacent modules (or other nearby heat sources)
can cause errors in thermocouple measurements by heating up the
terminals so that they are at a different temperature than the sensor
used to measure the cold junction. The thermal gradient generated
across the terminals can cause the terminals of different channels
to be at different temperatures, and so the resulting measurement
creates not only errors in absolute accuracy but also in the relative
accuracy between channels. The accuracy specifications for the
FP-TC-120 include the errors caused by a 0.2 °C (0.36 °F)
gradient. The actual gradient you can expect to encounter depends
on the terminal base you use and the details of your installation.
The following sections provide guidelines for estimating and
minimizing thermal gradients.
Estimating Thermal Gradients with the FP-TB-3
Isothermal Terminal Base
The FP-TB-3 is designed with isothermal construction to keep
the terminals at the same temperature. It is the terminal
base recommended for the best accuracy of thermocouple
measurements. Adjacent FieldPoint modules (either network
modules or I/O modules) create a thermal gradient across the
terminals of the FP-TB-3, which you can estimate by dividing
the larger of the amounts of heat dissipated by each of the adjacent
modules by 20 W/°C(11W/°F). For example, if the FP-TB-3 is
between an analog input module dissipating 0.35 W and a discrete
output module dissipating 3 W, the thermal gradient would be
3W÷ 20 W/ °C = 0.15 °C.
Estimating Thermal Gradients with the FP-TB-1
or FP-TB-2 Terminal Bases
The lack of isothermal construction in the FP-TB-1 and FP-TB-2
terminal bases makes them more susceptible to errors caused by
thermal gradients. These terminal bases are recommended for use
with thermocouple measurements only if such errors are
acceptable or if they can be minimized, as described in the
modules (either network modules or I/O modules) create a thermal
gradient across the terminals of the FP-TB-1, which you can
estimate by dividing the larger of the amounts of heat dissipated by
each of the adjacent modules by 1 W/°C (0.6 W/°F). For example,
if the FP-TB-1/2 is between an analog input module dissipating
0.35 W and a discrete output module dissipating 3 W, the thermal
gradient would be 3 W ÷ 1W/°C=3°C. The typical thermal
gradient created by the FP-TC-120 mounted on an FP-TB-1
(neglecting any adjacent modules) is about 0.2 °C.
The most common source of thermal gradients, particularly for the
FP-TB-1 and FP-TB-2, is the heat generated by adjacent modules.
For example, placing an FP-TB-1 next to an FP-1000 network
module can create more than a 1 °C thermal gradient. Mounted
thermocouple modules can be separated from the higher-power
modules by the lowest-power modules in your system or by the
FieldPoint Bus Extender Cable (part number 185576-15). This
precaution is generally not necessary with the FP-TB-3.
Hot or cold air draft can be another source of thermal gradients.
It is usually best to avoid having air blowing directly on the
terminals, although circulating air around other nearby
components may help them dissipate their heat and cause them
to be less of a source of thermal gradients on the terminal base.
Thermocouple wire also has the potential to be a significant source
of thermal gradients. Even the FP-TB-3 can be susceptible to these
errors. Heat or cold may be directly conducted to the terminal
junction by the thermocouple wire. If the thermocouple wires,
or objects they are in contact with, such as wiring ducts, near the
terminal base are at a different temperature than the terminals,
the wires transfer heat to or from the terminals and cause thermal
errors. To minimize these errors, follow these guidelines:
•Use small-gauge thermocouple wire. Smaller wires transfer
less heat.
•Run thermocouple wires together near the terminal base to
keep them at the same temperature.
•Avoid running thermocouple wires near hot or cold objects.
Specifications
The following specifications are typical for a range of
–40 to 70 °C, unless otherwise noted.
Electrical emissions .......................... EN 55011 Class A at 10 m
FCC Part 15A above 1 GHz
Electrical immunity ..........................Evaluated to EN 61326:
1997/A1: 1998, Table 1
For full EMC compliance, you must operate this
Note
device with shielded cabling. See the Declaration of
Conformity (DoC) for this product for any additional
regulatory compliance information. To obtain the DoC
for this product, click Declaration of Conformity at
ni.com/hardref.nsf/
.
Mechanical Dimensions
Figure 13 show the mechanical dimensions of the FP-TB-1/2/3
with an I/O module installed. Dimensions are given in millimeters
[inches].
107.19 [4.22]
109.5
[4.31]
91.44 [3.60]
Figure 13. Mechanical Dimensions
Where to Go for Support
For more information about setting up your FieldPoint system,
refer to these National Instruments documents:
•Your FieldPoint network module user manual
•Your other FieldPoint I/O module operating instructions
•Your FieldPoint terminal base operating instructions