National Instruments FIELDPOINT CFP-CB-1 User manual

cFP-CB-1

323322B-01 April 2003
©2002–2003 National Instruments Corp. All rights reserved.
FieldPoint™, National Instruments™, NI™, and ni.com™ are trademarks of National Instruments Corporation.
Product and company names mentioned herein are trademarks or trade names of their respective companies.
For patents covering National Instruments products, refer to the appropriate location: Help»Patents in your software,
the patents.txt file on your CD, or ni.com/patents.
FieldPoint Operating Instructions
cFP-CB-1 and cFP-CB-3
Compact FieldPoint Connector Blocks
These operating instructions describe how to install and use the
cFP-CB-1 and cFP-CB-3 (referred to inclusively as the cFP-CB-x).
Features
The cFP-CB-1 and cFP-CB-3 are Compact FieldPoint connector
blocks with the following features:
• cFP-CB-1 is designed for general-purpose and hazardous
voltage1operation with all Compact FieldPoint I/O modules
• Isothermal construction of cFP-CB-3 minimizes temperature
gradients for use with thermocouples
• Mount on a cFP-BP-xCompact FieldPoint backplane
• 36 terminals available (cFP-CB-3 has 18)
• Tie-wrap anchors for wires
• Color-coded V and C terminals for voltage supply and
common connections
• –40 to 70 °C operation
1 Hazardous voltage is voltage greater than 30 Vrms/42.4 V peak or 60 VDC.

cFP-CB-1 and cFP-CB-3 2 ni.com
Figure 1. cFP-CB-1 Parts Locator Diagram
Note Earlier cFP-CB-1 connector blocks have a different
screw-terminal numbering arrangement.
Figure 2. cFP-CB-3 Parts Locator Diagram
1 Tie-Wrap Anchors
2 Screw Hole for Strain-Relief Bar
3 Screw Terminals
4 Screw Hole for Top Cover
5 Mounting Screw
6 37-Pin I/O Connector
1 Tie-Wrap Anchors
2 Screw Hole for Strain-Relief Bar
3 Overlay Showing Channel
Assignments of Screw Terminals
4 Screw Hole for Top Cover
5 Mounting Screw
6 Screw Terminals
7 37-Pin I/O Connector
CC
6
5
4
3
2
1
CC
cFP-TC-120
+ –
CH 0
+ –
CH 1
+ –
CH 2
+
CH 3
–
CH 4
+ –
CH 5
+ –
CH 6
+ –
CH 7
TERMINAL
ASSIGNMENTS
–+
76
5
4
3
2
1

© National Instruments Corp. 3 cFP-CB-1 and cFP-CB-3
Wiring to the Connector Block
Refer to the I/O module operating instructions for information
about wiring configurations, including detailed wiring diagrams
and fuse recommendations.
Note To protect the FieldPoint system and connected
devices, install appropriate external fuses on all screw
terminals. Refer to the Specifications section for the
current limits of the cFP-CB-xscrew terminals.
Note The V terminals are internally connected to each
other and the C terminals are internally connected to each
other.
Caution Ensure that hazardous voltage wiring is
performed only by qualified personnel adhering to local
electrical standards.
1. Loosen the top cover screws and remove the cover. Refer to
Figure 3.
Figure 3. Removing the Top Cover from the cFP-CB-x
2. Verify that there are no cuts in the wire insulation that can
cause a safety hazard.
3. Strip 6 mm (0.24 in.) of insulation from the ends of the wires.

cFP-CB-1 and cFP-CB-3 4 ni.com
4. Insert the entire stripped ends of the wires into the appropriate
screw terminals. Do not allow any bare wire to show outside
the screw terminals.
5. Using a 1/8 in. flathead screwdriver, tighten the screw
terminals to 0.5–0.6 N ⋅m (4.4–5.3 lb ⋅in.) of torque.
Installing the Strain-Relief Bar
The cFP-CB-1 is shipped with two strain-relief bars, one with a
foam cushion for wires and one with grooves for jacketed cables.
The cFP-CB-3 has one foam-cushion strain relief bar. The tie-wrap
anchors on the connector block provide additional strain relief.
Figure 4 shows the two strain-relief bars.
Figure 4. cFP-CB-xStrain-Relief Bars
Choose the strain-relief bar that suits your application and
complete the following steps:
1. Using a number 2 Phillips screwdriver, install the strain-relief
bar on the connector block as shown in Figure 5.
Figure 5. Installing the Strain-Relief Bar

© National Instruments Corp. 5 cFP-CB-1 and cFP-CB-3
2. Tighten the strain-relief screws. If you are using the cushioned
strain-relief bar, make sure all the wires are secure against the
cushion and not touching metal parts of the connector block.
3. Reinstall the top cover and tighten the top cover screws.
4. Install tie wraps as shown in Figure 6.
Figure 6. Tie Wraps
Installing the cFP-CB-x
To install the cFP-CB-x, refer to Figure 7 and complete the
following steps:
1. Align the captive screws on the cFP-CB-xwith the holes on the
backplane. The shape of the I/O connector on the cFP-CB-x
prevents backward insertion.
2. Press firmly to seat the cFP-CB-xon the backplane.
3. Using a number 2 Phillips screwdriver with a shank of at least
64 mm (2.5 in.) length, tighten the captive screws to 1.1 N ⋅m
(10 lb ⋅in.) of torque. The nylon coating on the screws prevents
them from loosening.
Front View Rear View

cFP-CB-1 and cFP-CB-3 6 ni.com
Figure 7. Installing the cFP-CB-x
Thermocouple Wiring
Compact FieldPoint thermocouple input modules can measure the
temperature of the terminals on the cFP-CB-1 or cFP-CB-3
connector block. The modules use this measurement, called the
cold junction temperature, to compensate for the thermoelectric
voltages generated at these junctions. For the most accurate
cold-junction compensation, use the cFP-CB-3 for connecting
thermocouple signals.
Heat dissipated by adjacent modules (or other nearby heat sources)
can cause errors in thermocouple measurements by heating the
terminals to 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 differ
in temperatures. The resulting measurement creates errors in
1 Connector Block Captive Screws
2 I/O Module
3 Screw Holes for Connector Block
4 Socket for Connector Block
3
4
3
2
1
1

© National Instruments Corp. 7 cFP-CB-1 and cFP-CB-3
absolute and relative accuracy between channels. The actual
thermal gradient depends on the connector block you use and
the details of your installation. The following section provides
guidelines for minimizing thermal gradients.
Minimizing Thermal Gradients
To minimize the thermal gradient across the terminals, use the
cFP-CB-3 for connecting thermocouple signals. The cFP-CB-3 is
designed with isothermal construction to keep the terminals at the
same temperature. In addition to using the cFP-CB-3, you can
minimize thermal gradients by following these guidelines:
• Do not place power supplies or other heat sources directly
above or below the Compact FieldPoint system.
• Do not install high-power modules, such as the cFP-DO-4xx
and cFP-RLY-4xx, adjacent to the cFP-CB-3.
• Use small-gauge thermocouple wire to transfer less heat.
• Run thermocouple wires together near the connector block to
keep them at the same temperature.
• Avoid running thermocouple wires near hot or cold objects.
• Use the foam cushion strain relief to restrict air flow.
Isolation and Safety Guidelines
Caution Read the following information before
attempting to connect the cFP-CB-xto any circuits that
may contain hazardous voltages.
This section describes the isolation of the cFP-CB-xand its
compliance with international safety standards. The field wiring
connections are isolated from the backplane and the inter-module
communication bus. The isolation is provided by the module,
which has optical and galvanic isolation barriers designed and
tested to protect against transient fault voltages of up to 2,300 Vrms.
The cFP-CB-xprovides double insulation (compliant with
IEC 61010-1) for working voltages of 250 Vrms1. Safety standards
(such as those published by UL and IEC) require the use of double
insulation between hazardous voltages and any human-accessible
parts or circuits.
1 Working voltage is defined as the signal voltage plus the common-mode voltage.
Common-mode voltage is the voltage of the module with respect to ground.

cFP-CB-1 and cFP-CB-3 8 ni.com
Never try to use any isolation product between human-accessible
parts (such as DIN rails or monitoring stations) and circuits that
can be at hazardous potentials under normal conditions, unless the
product is specifically designed for such an application as is the
cFP-CB-x.
Even though the cFP-CB-xis designed to handle applications with
hazardous potentials, follow these guidelines to ensure a safe total
system:
• The cFP-CB-xhas a safety isolation barrier between the
I/O channels and the inter-module communication bus. There
is no isolation between channels unless otherwise noted. If any
of the channels on a module are wired at a hazardous potential,
make sure that all other devices or circuits connected to that
module are properly insulated from human contact.
•Donot share the external supply voltages (the V and C
terminals) with other devices (including other FieldPoint
devices), unless those devices are isolated from human contact.
• You must connect the protective earth (PE) ground terminal on
the cFP-BP-xbackplane to the system safety ground. The
backplane PE ground terminal has the following symbol
stamped beside it: . Connect the backplane PE ground
terminal to the system safety ground using 14 AWG (1.6 mm)
wire with a ring lug. Use the 5/16 in. panhead screw shipped
with the backplane to secure the ring lug to the backplane PE
ground terminal.
• As with any hazardous voltage wiring, make sure that all
wiring and connections meet applicable electrical codes and
commonsense practices. Mount the backplane in an area,
position, or cabinet that prevents accidental or unauthorized
access to wiring that carries hazardous voltages.
• The isolation of the cFP-CB-xis certified as double-insulated
for working voltages of 250 Vrms. Do not use the cFP-CB-xas
the only isolating barrier between human contact and working
voltages of more than 250 Vrms.
• Operate the cFP-CB-xonly at or below Pollution Degree 2.
Pollution Degree 2 means that only nonconductive pollution
occurs in most cases. Occasionally, however, a temporary
conductivity caused by condensation must be expected.

© National Instruments Corp. 9 cFP-CB-1 and cFP-CB-3
•Donot operate FieldPoint products in an explosive atmosphere
or where there may be flammable gases or fumes. If you need
to operate FieldPoint products in such an environment, the
FieldPoint products must be in a suitably rated enclosure.
• Operate the cFP-CB-xat or below Installation Category II.
Installation Category II is for measurements performed on
circuits directly connected to the electrical distribution system.
This category refers to local-level distribution, such as that
provided by a standard wall outlet.
Specifications
The following specifications are typical for the range –40 to 70 °C,
unless otherwise noted.
Installation
Terminal wiring ................................ 16–26 AWG copper
conductor wire with 6 mm
(0.24 in.) of insulation
stripped from the end1
Maximum cable diameter ................. 8 mm (5/16 in.) with
cable-grooved strain relief
Torque for screw terminals ............... 0.5–0.6 N ⋅m
(4.4–5.3 lb ⋅in.)
Maximum current for screw terminals2
V and C terminals....................... 4 A
All other terminals...................... 2 A
Accuracy
Cold-junction accuracy ..................... 0.15 °C typ, 0.3 °C max
There is typically an additional 0.2 °C difference between the
temperature of the cold-junction sensor and that of the actual
terminals.
1 Use only copper conductor wire unless you are working with a sensing device, such
as a thermocouple, that requires a different type of wire.
2 Use fast-acting fuses to limit the current through screw terminals. Some I/O module
terminals require a lower maximum current value. Refer to the I/O module operating
instructions for more information.