National Instruments TC-2095 User manual

INSTALLATION GUIDE
BNC/TC-2095 Rack-Mount Adapter
This installation guide describes how to install the National Instruments
BNC-2095 and the TC-2095 rack-mount adapters and use them with
SCXI-1100, SCXI-1102/B/C, and SCXI-1104/C modules. The BNC-2095
also can be used with the SCXI-1581.
The BNC-2095 adapter has 32 BNC connectors to connect field signals to
the SCXI module inputs. The TC-2095 adapter has 32 uncompensated
miniconnectors to connect the thermocouples to the SCXI module inputs.
Both the BNC-2095 and TC-2095 adapters have the following features:
• A 96-pin connector to connect to the SCXI module using an SH96-96
shielded cable or an R9696 ribbon cable
• Rack-mount construction for use with 19-in. racks
• A shielded, metal enclosure to minimize noise
The TC-2095 also features isothermal construction to minimize the
temperature gradients across the thermocouple junctions and a
high-accuracy thermistor for cold-junction temperature sensing.
The BNC-2095 and the TC-2095 have pull-up resistors connected between
CH+ and +5 VDC and ground-referencing resistors connected between
CH– and chassis ground through switches located on the rear of the adapter.
The bias resistor is a ground-referencing pull-down resistor for referencing
floating signals; the pull-up resistor is used for open thermocouple
detection. The pull-up resistors enable open thermocouple detection by
detecting saturation in the SCXI module amplifier output and
ground-referenced floating signals.

BNC/TC-2095 Rack-Mount Adapter Installation Guide 2 ni.com
Conventions
The following conventions are used in this guide:
♦The ♦symbol indicates that the text following it applies only to a specific
product, a specific operating system, or a specific software version.
<> Angle brackets that contain numbers separated by an ellipsis represent a
range of values associated with a bit or signal name—for example,
DBIO<3..0>. Angle brackets also can denote a variable in a channel
name—for example, ACH<i>.
»The »symbol leads you through nested menu items and dialog box options
to a final action. The sequence File»Page Setup»Options directs you to
pull down the File menu, select the Page Setup item, and select Options
from the last dialog box.
This icon denotes a note, which alerts you to important information.
This icon denotes a caution, which advises you of precautions to take to
avoid injury, data loss, or a system crash. When this symbol is marked on
the product, refer to the Read Me First: Safety and Radio-Frequency
Interference document, shipped with the product, for precautions to take.
When symbol is marked on a product it denotes a warning advising you to
take precautions to avoid electrical shock.
When symbol is marked on a product it denotes a component that may be
hot. Touching this component may result in bodily injury.
bold Bold text denotes items that you must select or click in the software, such
as menu items and dialog box options. Bold text also denotes parameter
names and hardware labels.
italic Italic text denotes variables, emphasis, a cross reference, or an introduction
to a key concept. This font also denotes text that is a placeholder for a word
or value that you must supply.
monospace Text in this font denotes text or characters that you should enter from the
keyboard, sections of code, programming examples, and syntax examples.
This font is also used for the proper names of disk drives, paths, directories,
programs, subprograms, subroutines, device names, functions, operations,
variables, filenames and extensions, and code excerpts.

©National Instruments Corporation 3 BNC/TC-2095 Rack-Mount Adapter Installation Guide
What You Need To Get Started
To install and use the BNC/TC-2095, you need the following items:
❑One of the following:
– BNC-2095 rack-mount adapter with BNC connectors
– TC-2095 rack-mount adapter with thermocouple miniconnectors
❑BNC/TC-2095 Rack-Mount Adapter Installation Guide
❑Read Me First: Safety and Radio-Frequency Interference
❑Four 10 MΩ resistor networks
❑SCXI chassis and documentation
❑One of the following SCXI modules and its documentation:
– SCXI-1100
– SCXI-1102/B/C
– SCXI-1104/C
– SCXI-1581
❑One of the following cable assemblies:
– SH96-96 cable assembly (recommended)
– R9696 cable assembly
❑TBX cable adapter (included in cable assembly kit)
❑Number 1 Phillips screwdriver
❑1/8 in. flathead screwdriver
❑Long-nose pliers
Connecting Signals
Caution Refer to the Read Me First: Safety and Radio-Frequency Interference document
before removing equipment covers or connecting/disconnecting any signal wires.
This section describes how to connect field signals to the adapter and how
to connect the adapter to the SCXI module.

BNC/TC-2095 Rack-Mount Adapter Installation Guide 4 ni.com
Connecting Field Signals
♦BNC-2095
The BNC-2095 has 32 BNC connectors, one for each channel of a
SCXI module. Each BNC connector is labeled with the corresponding
channel number. The center pin of the BNC connector is the CH+, and
the outer shield is the CH– of each channel. The CH– is isolated from
the chassis ground, so you can use it for ground-referenced differential
signals. To ensure CH– is isolated from chassis ground, do not use bias
resistors.
Caution Do not force the BNC connector on the BNC-2095. If you have difficulty making
the connection, completely remove the connector and try again.
Connect the BNC connector of the cable to the BNC connector of the
BNC-2095 by aligning and inserting the connector and turning the
cable connector clockwise.
♦TC-2095
The TC-2095 has 32 universal thermocouple miniconnectors that you
can use to connect a thermocouple to each channel of the SCXI
module. Each connector is labeled with the corresponding channel
number. The miniconnector indicates the positive and negative
terminals.
Caution Do not force the miniconnector into the socket. If you have difficulty inserting the
miniconnector, check that the polarity is correct.
Connect the thermocouple wire to the TC-2095 by inserting the
miniconnector into the socket. Each miniconnector consists of two
spades of different widths. The differing widths guarantee correct
polarity if both connectors are correctly wired.
Both contacts of the thermocouple miniconnector are made of copper.
This could cause offset errors in T-, R-, and S-type thermocouple
measurements because each of these types of thermocouples has
one copper contact. Only one contact forms a cold junction with
T, R, and S-type thermocouples.

©National Instruments Corporation 5 BNC/TC-2095 Rack-Mount Adapter Installation Guide
Configuring Open-Thermocouple/Signal Detection and Signal
Ground-Referencing
Refer to Table 1 to configure the BNC/TC-2095 for operating with
open-thermocouple or signal detection, and for properly
ground-referencing the signals.
Table 1. Configuring Open-Thermocouple/Signal Detection and Signal Ground-Referencing
Switch Settings Signal Type
Detects
Open
Thermocouple Comments
Floating signal or
thermocouple
Yes BNC-2095—Use this
setting for detecting
floating signals or open
signal leads. When
detecting open signal
leads, the positive input is
pulled to +5 VDC if the
measured signal is
<5 VDC. Only use this
setting or configuration
with signals between
±5 VDC.
TC-2095—Use this setting
to detect open
thermocouples and when
the thermocouple is
floating.
Ground-referenced
signal or
thermocouple
No BNC-2095 or
TC-2095—Use this setting
when the signal or
thermocouple is
ground-referenced and
you want to disable
open-thermocouple
detection.
1
O
N
23 45678
GND REF
CH
OFF
ON
PULL-UP
GND REF
PULL-UP
GND REF
PULL-UP
GND REF
PULL-UP
3
2
1
0
1
O
N
23 45678
GND REF
CH
OFF
ON
PULL-UP
GND REF
PULL-UP
GND REF
PULL-UP
GND REF
PULL-UP
3
2
1
0

BNC/TC-2095 Rack-Mount Adapter Installation Guide 6 ni.com
Caution Connecting an external ground-referenced signal with the 10 Ω resistor network
in place can cause permanent damage to the resistor network and the traces on the
BNC/TC-2095 printed circuit board. NI is not liable for any damage or injuries resulting
from improper signal connections. Refer to the Temperature Sensor Output and Accuracy
section for more information.
Connecting the BNC/TC-2095 to the SCXI Module
Complete the following steps to mount the SH96-96 cable assembly and
connect the BNC/TC-2095 to the SCXI module. Refer to Figures 1 and 2
as needed.
Floating
thermocouple or
signal
No BNC-2095 or
TC-2095—Use this setting
when the signal or
thermocouple is floating
and you want to disable
open-thermocouple
detection.
Ground-referenced
thermocouple or
signal
Yes BNC-2095—Use this
setting for detecting
ground-referenced signals
or open signal leads.
When detecting open
signal leads, the positive
input is pulled to +5 VDC
if the measured signal is
<5 VDC. Only use this
setting or configuration
with signals between
±5 VDC.
TC-2095—Use this setting
to detect open
thermocouples for
ground-referenced
thermocouples.
Table 1. Configuring Open-Thermocouple/Signal Detection and Signal Ground-Referencing (Continued)
Switch Settings Signal Type
Detects
Open
Thermocouple Comments
1
O
N
23 45678
GND REF
CH
OFF
ON
PULL-UP
GND REF
PULL-UP
GND REF
PULL-UP
GND REF
PULL-UP
3
2
1
0
1
O
N
23 45678
GND REF
CH
OFF
ON
PULL-UP
GND REF
PULL-UP
GND REF
PULL-UP
GND REF
PULL-UP
3
2
1
0

©National Instruments Corporation 7 BNC/TC-2095 Rack-Mount Adapter Installation Guide
Caution Refer to the Connecting Signals section before connecting the signals. If signal
wires are connected to the terminal block, dangerous voltages can exist even when the
equipment is powered off.
1. Power off the SCXI chassis.
2. Power off the computer that contains the E Series data acquisition
(DAQ) device, or disconnect the computer from the SCXI chassis.
3. Connect the TBX cable adapter to the SCXI module, and secure the
adapter by tightening both thumbscrews.
4. Connect either end of the SH96-96 cable to the TBX cable adapter and
SCXI module, and secure the cable by tightening both backshell
mounting screws.
Figure 1. Connecting the SH96-96 Cable to the SCXI Module
5. Mount the BNC/TC-2095 onto a 19-in. rack or place it on a workbench
near the SCXI chassis. If you do not rack-mount the BNC/TC-2095,
attach the four adhesive rubber feet included in the kit to the bottom of
the adapter to keep it stationary.
1 Backshell Mounting Screws
2 SH96-96 Cable
3 Thumbscrews
4 SCXI Chassis
5 TBX Cable Adapter
3
4
3
1
5
1
2
5
4
3
2
1
ADDRESS

BNC/TC-2095 Rack-Mount Adapter Installation Guide 8 ni.com
Note To minimize the temperature gradient inside the TC-2095 and maintain its
isothermal properties for accurate cold-junction compensation, keep the adapter from
extreme temperature differentials.
6. Connect the other end of the 96-pin cable to the BNC/TC-2095 96-pin
connector and screw down the backshell.
Caution The cable connectors of the cables are keyed. Do not force the connection. If you
encounter difficulty, verify that the keying of the cable connectors is correct.
Figure 2. BNC/TC-2095 Connected to SCXI Module
Configuring the BNC/TC-2095
To access jumpers W1 and W2 and the resistor networks, refer to Figure 3
as you complete the following steps:
1. Remove the nine cover screws that secure the BNC/TC-2095 cover.
2. Remove the cover.
3. Set jumpers W1 and W2 as needed. For more information about setting
the jumpers, refer to the Configuring the Shield Ground Jumper and
Configuring the Cold-Junction Sensor (TC-2095 Only) sections.
4. Replace the cover and secure it with the cover screws.
1 BNC/TC-2095 2 96-Pin Backshell 3 SCXI Chassis
1
O
N
2345678
1
O
N
2345678
1
O
N
2345678
1
O
N
2345678
1
O
N
234567 8
1
O
N
2345678
1
O
N
2345678
1
O
N
2345678
1
5
4
3
2
1
ADDRESS
2 32

©National Instruments Corporation 9 BNC/TC-2095 Rack-Mount Adapter Installation Guide
Figure 3. BNC-2095 Parts Locator Diagram
Configuring the Shield Ground Jumper
Jumper W2 connects the metal case and shield to the analog ground of the
SCXI module directly or through a 100 Ω resistor. The factory-default
setting is through the 100 Ω resistor. Refer to Table 2 for configuration
options for jumper W2.
1) Cover
2) Cover Screws (9)
3) RP1
4) RP5
5) RP2
6) RP5
7) W1
8) W2
9) RP3
10) RP7
11) RP4
12) RP8
13) Switches
12 11 10 98
7
65
43
13
2
1

BNC/TC-2095 Rack-Mount Adapter Installation Guide 10 ni.com
Table 2. BNC/TC-2095 Shield Ground Jumper Configuration
Jumper W2 Configuration Description When to Use a Setting
100 Ω(factory-default)—
Connects the
BNC/TC-2095 housing
to SCXI chassis ground
through a 100 Ω resistor,
while minimizing any
potential ground loop
current.
Use this setting when you are using
the SH96-96 cable, and if one of the
following is true:
• You have not rack-mounted the
BNC/TC-2095.
• You have rack-mounted the
BNC/TC-2095, but are unsure
whether the rack and the
BNC/TC-2095 are grounded.
0 Ω—Connects the
BNC/TC-2095 housing to
SCXI chassis ground.
Use this setting only if the
factory-default setting is inadequate
for noise rejection, you are using the
R9696 cable, and if one of the
following is true:
• You have not rack-mounted the
BNC/TC-2095.
• You have rack-mounted the
BNC/TC-2095 and are sure that
the rack and the BNC/TC-2095
are not grounded.
Open—Disconnects the
BNC/TC-2095 metal
housing from SCXI
chassis ground.
Use this setting only if all of the
following are true:
• Factory-default setting was
inadequate for noise rejection.
• You are using either the SH96-96
cable or the R9696 cable.
• You have rack-mounted the
BNC/TC-2095.
• You are sure that the rack and the
BNC/TC-2095 are grounded.
0 Ω
100 Ω
OPEN
4321
W2
0 Ω
100 Ω
OPEN
4321
W2
0 Ω
100 Ω
OPEN
4321
W2