National Instruments BNC-2120 User manual

INSTALLATION GUIDE
BNC-2120
Connector Accessory for E/M/S/X Series Devices
This installation guide describes how to install, configure, and use your BNC-2120 accessory
with 68-pin or 100-pin E/M/S/X Series multifunction data acquisition (DAQ) devices. This
document also contains accessory specifications.
The BNC-2120 has the following features:
• Eight BNC connectors for analog input (AI) connection
• Onboard temperature reference
• Thermocouple connector
• Resistor measurement screw terminals
• Two BNC connectors for analog output (AO) connection
• Screw terminals for digital I/O (DIO) connection with state indicators
• Screw terminals for timing I/O (TIO) connection
• Two user-defined BNC connectors
• A function generator with the following outputs:
– Frequency-adjustable, TTL-compatible square wave
– Frequency- and amplitude-adjustable sine wave or triangle wave
• Quadrature encoder
• A 68-pin I/O connector that connects to multifunction DAQ devices
• Can be used on a desktop or mounted on a DIN rail
Contents
What You Need to Get Started ................................................................................................. 2
Installing the BNC-2120........................................................................................................... 2
Connecting Analog Input Signals............................................................................................. 5
Connecting Differential Analog Input Signals ................................................................. 6
Measuring Floating Signals ...................................................................................... 6
Measuring Ground-Referenced Signals.................................................................... 7
Measuring Temperature.................................................................................................... 7
Measuring Resistance ....................................................................................................... 8
Connecting Analog Output Signals .......................................................................................... 8
Using the Function Generator................................................................................................... 9
Connecting Timing I/O Signals ................................................................................................ 9
Using the Quadrature Encoder ......................................................................................... 12
Connecting User-Defined Signals ............................................................................................ 13
Connecting Digital I/O Signals................................................................................................. 14
Specifications............................................................................................................................ 14

2|ni.com |BNC-2120 Installation Guide
What You Need to Get Started
To set up and use your BNC-2120 accessory, you need the following:
BNC-2120 accessory/accessories1
BNC-2120 Installation Guide
One of the following DAQ devices:
– 68-pin E/M/S/X Series device (with one or two I/O connectors)2
– 100-pin E Series device
Cable(s) for DAQ device(s), as listed in Table 1
The E Series User Manual, the M Series User Manual, the S Series User Manual, or the
X Series User Manual
BNC cables
28–16 AWG wire
Wire strippers
Flathead screwdriver
Installing the BNC-2120
Caution When this symbol is marked on a product, refer to the Read Me First:
Safety and Radio-Frequency Interference document for information about
precautions to take.
Figure 1 shows the front panel of the BNC-2120.
1 You can use two BNC-2120 accessories with both connectors of two connector M/X Series devices.
2 You cannot use the BNC-2120 with Connector 1 of NI 6225/6255 devices.

BNC-2120 Installation Guide |© National Instruments |3
Figure 1. BNC-2120 Front Panel
1 RES/BNC Switch (AI 3)
2 Resistor Measurement
Screw Terminals
3 Thermocouple Input
Connector
4 Temperature Reference
5 BNC/Temp. Ref. Switch (AI 0)
6 BNC/Thermocouple
Switch (AI 1)
7 Analog Input BNC
Connectors
8 FS/GS Switches
9 Analog Output BNC
Connector
10 Frequency Range Selection
Switch
11 Sine/Triangle BNC Connector
12 TTL Square Wave BNC
Connector
13 Sine/Triangle Waveform
Switch
14 Frequency Adjust Knob
15 Amplitude Adjust Knob
16 Digital I/O Screw Terminals
17 Digital I/O LEDs
18 User-Defined Screw Terminals
19 User-Defined BNC
Connectors
20 Timing I/O Screw Terminals
21 Quadrature Encoder Screw
Terminals
22 Quadrature Encoder Knob
23 Timing I/O BNC Connector
24 Power Indicator LED
E
L
R
T
T
S
NI
NA
M
U
N
O
IA
S
TN
_
+Floating
Source (FS)
_
+
Ground Ref.
Source (GS)
AO
ANALOG OUTPUTS
ANALOG INPUTS
DIGITAL I/O
FUNCTION GENERATOR
Frequency Selection
Amplitude Adjust
Sine /Triangle TTL Square Wave
Frequency Adjust
GSFS GSFS
GSFS GSFS
GSFS GSFS
GSFS GSFS
AI 0 AI 1
USER 1
USER 2
P0.7
P0.6
P0.5
P0.4
P0.3
P0.2
P0.1
P0.0
D GND
AI 2
BNC
RES+
AI GND
AI SENSE
RES-
1
2
3
4
Temp.
Ref.
0.1-10 kHz
LO HI LO HI
1-100 kHz 13-1000 kHz
Thermo
couple
BNC
RES
AI 3
BNC
AI 3
AI 4 AI 5
AI 6 AI 7
AO 0 AO 1
USER-DEFINED
SIGNALS*
*For BNC connections, wire
anyTiming I/O or Digital I/O
screw terminals here.
PWR
BNC-2120
TIMING I/O
PFI 0 / P1.0
96 Pulses/ Rev
Quadrature
Encoder
PFI 1 / P1.1
PFI 2 / P1.2
PFI 3 / P1.3
PFI 4 / P1.4
PFI 5 / P1.5
PFI 6 / P1.6
PFI 7 / P1.7
PFI 8 / P2.0
PFI 9 / P2.1
PFI 12 / P2.4
PFI 13 / P2.5
PFI 14 / P2.6
+5 V
PULSES
UP/DN
D GND
1.
2.
3.
4.
!
10
16
17
1
5
7
9
8
4
6
2
12
14
13
11
15
19
20
23
22
24
21
3
18

4|ni.com |BNC-2120 Installation Guide
To connect the BNC-2120 to your DAQ device, complete the following steps. Consult your
computer or PXI/PXI Express chassis user manual for specific instructions and warnings.
Note If you have not already installed your DAQ device, refer to the DAQ Getting
Started guides for instructions.
Caution Do not connect the BNC-2120 to any device other than National
Instruments E/M/S/X Series multifunction DAQ devices. Doing so can damage the
BNC-2120, the DAQ device, or the host computer. National Instruments is not liable
for damage resulting from these connections.
1. Place the BNC-2120 near the host computer or PXI/PXI Express chassis or use the optional
DIN Rail Mounting kit for UMI-FLEX-6 and BNC boxes (Part Number 777972-01), which
you can order from National Instruments at ni.com.
Caution Do not connect input voltages greater than 42.4 Vpk/60 VDC to the
BNC-2120. The BNC-2120 is not designed for any input voltages greater than
42.4 Vpk/60 VDC, even if a user-installed voltage divider reduces the voltage to within
the input range of the DAQ device. Input voltages greater than 42.4 Vpk/60 VDC can
damage the BNC-2120, all devices connected to it, and the host computer. Overvoltage
can also cause an electric shock hazard for the operator. National Instruments is not
liable for damage or injury resulting from such misuse.
2. Connect the BNC-2120 to the DAQ device using the appropriate cable for your DAQ
device, as listed in Table 1.
Caution To ensure the specified EMC performance, operate this product only with
shielded cables and accessories.
Table 1. BNC-2120 Cabling Options
Number
of Pins DAQ Device
Shielded
Recommended Cable
Unshielded
Cable
68-pin DAQCard E Series,
NI PCI/PCIe/PXI/PXIe M Series*
NI 6143 S Series,
PCIe/PXIe/USB X Series
SHC68-68-EPM RC68-68
PCI/PXI E Series,
USB Mass Termination M Series*,
NI 611x/612x/613xS Series†
SH68-68-EPM R6868†
100-pin PCI/PXI E Series SH1006868 —
Caution: For compliance with Electromagnetic Compatibility (EMC) requirements, this product must
be operated with shielded cables and accessories. If unshielded cables or accessories are used, the EMC
specifications are no longer guaranteed unless all unshielded cables and/or accessories are installed in a
shielded enclosure with properly designed and shielded input/output ports.
*You cannot connect the BNC-2120 to Connector 1 of NI 6225/6255 devices.
†Do not use the R6868 cable with NI 6115/6120 S Series devices; use only the SH68-68-EPM cable.

BNC-2120 Installation Guide |© National Instruments |5
The power indicator LED, shown in Figure 1, lights. If it does not light, check the cable
connections.
3. Launch Measurement & Automation Explorer (MAX), confirm that your DAQ device is
recognized, and configure your device settings. Refer to the DAQ Getting Started guides
for more information.
4. Connect signals to the BNC connectors and screw terminal block as described in the
following sections.
Caution To ensure the specified EMC performance, operate this product only with
shielded cables and accessories. When connecting signals to the screw terminal
blocks, the wires must be shielded (e.g. one conductor of a shielded, multi-conductor
cable). The cable shield must be terminated to the D GND or AI GND terminal of the
terminal block using as short a connection as is practical.
Note With NI-DAQmx, National Instruments has revised its terminal names so
they are easier to understand and more consistent among NI hardware and software
products. The revised terminal names used in this document are usually similar to the
names they replace. For a complete list of Traditional NI-DAQ (Legacy) terminal
names and their NI-DAQmx equivalents, refer to the Terminal Name Equivalents
table in the NI-DAQmx Help.
5. Test specific device functionality, such as the ability to send and receive data with MAX
test panels. Refer to the DAQ Getting Started guides for detailed information about running
test panels in MAX.
When you have finished using the BNC-2120, power off any external signals connected to the
BNC-2120 before you power off your computer.
Connecting Analog Input Signals
You can use the analog input BNCs on the BNC-2120 in the following ways:
• Measure differential AI signals, as described in the Connecting Differential Analog Input
Signals section
• Measure temperature, as described in the Measuring Temperature section
• Measure resistance, as described in the Measuring Resistance section

6|ni.com |BNC-2120 Installation Guide
Connecting Differential Analog Input Signals
Use the BNC-2120 BNC connectors on the front panel to connect AI <0..7> signals to your
DAQ device. The BNC-2120 is only intended for differential analog input signals. The number
of connectors you use depends on your DAQ device and application. Complete the following
steps to measure a differential (DIFF) analog input signal.
1. Connect the BNC cable to one of the AI <0..7> BNC connectors on the front panel.1
2. If you are using AI 0, move the BNC/Temp. Ref. switch to the BNC position.
If you are using AI 1, move the BNC/Thermocouple switch to the BNC position.
If you are using AI 3, move the RES/BNC switch to the BNC position.
3. Configure your software to measure the channel differentially.
4. Move the FS/GS switch to the applicable position, depending on whether you are
measuring a floating source (FS) or ground-referenced source (GS) analog input signal.
Refer to the Measuring Floating Signals and Measuring Ground-Referenced Signals
sections for more information about these signal sources.
Measuring Floating Signals
To measure floating signal sources, move the corresponding switch below the BNC connector
to the FS position. In the floating source switch position, the DAQ device’s amplifier negative
terminal connects to ground through a 4.99 kΩresistor, as shown in Figure 2. Refer to your
DAQ device documentation for more information about measuring floating signals.
Figure 2. Measuring a Floating Signal Source
1 When using the BNC-2120 with Connector 1 of two connector M/X Series devices, the AI <0..7> BNCs
on the BNC-2120 map to the AI <16..23> channels on the device.
+
–
Signal
Source BNC-2120
DAQ Device
(Differential Input Mode)
AI GND
+
–
4.99 kΩ
FS
FSMode
0.1 μF

BNC-2120 Installation Guide |© National Instruments |7
Measuring Ground-Referenced Signals
To measure ground-referenced signals, move the switch below the BNC connector for the
AI channel you are using to the GS position. Using the ground-referenced source switch position
avoids ground loops, as shown in Figure 3. Refer to your DAQ device documentation for more
information about measuring ground-referenced signals.
Figure 3. Measuring a Ground-Referenced Signal Source
AI GND and AI SENSE signals are located at the analog input screw terminals of the
BNC-2120. When connecting signals to the screw terminals, use 28–16 AWG wire with the
insulation stripped to 0.28 in.
Measuring Temperature
You can measure temperature on the BNC-2120 with the temperature reference and
thermocouple connector.
To use the integrated circuit (IC) temperature reference on the BNC-2120, move the BNC/Temp.
Ref. switch above the AI 0 BNC to Temp. Ref. The integrated circuit (IC) temperature reference
provides built-in cold-junction compensation (CJC) through software. The IC sensor voltage is
linearly proportional to the sensor temperature where:
°C = Volts ×100
The sensor is accurate to ±1.5 °C.
To use the thermocouple on the BNC-2120, move the BNC/Thermocouple switch above the AI 1
BNC to Thermocouple. You can connect any type of thermocouple with a two-prong miniature
or subminiature male connector to the thermocouple connector.
For more information on thermocouples and CJC, refer to the Developer Zone document, Taking
Thermocouple Temperature Measurements, by going to ni.com/info and entering the Info
Code rdtttm.
+
–
Signal
Source BNC-2120
DAQ Device
(Differential Input Mode)
AI GND
+
–
4.99 kΩ
GS
GSMode
0.1 μF

8|ni.com |BNC-2120 Installation Guide
Measuring Resistance
You can measure resistance with the analog input screw terminals on the BNC-2120. Figure 4
is a schematic representation of how the BNC-2120 measures resistance.
Figure 4. Measuring Resistance on the BNC-2120
RES+ is internally connected to AI 3 and VCC. RES– is internally connected to AI 11. There is
also a 10 kΩresistor between AI 11 and AI GND.
When connecting signals to the screw terminals, use 28–16 AWG wire with the insulation
stripped to 0.28 in.
Complete the following steps to measure resistance.
1. Move the RES/BNC switch above the AI 3 BNC to the RES position.
2. Configure your software to measure AI 3 and AI 11 in referenced single-ended (RSE)
mode.
3. Connect the resistor to the RES+ and RES– screw terminals.
You can measure resistors with values ranging from 100 Ωto 1 MΩ.
4. Measure VCC on AI 3 and the voltage drop across the internal 10 kΩresistor on AI 11.
5. With these measurements, calculate the resistor value using the following formula:
Connecting Analog Output Signals
Use the AO <0..1> BNC connectors on the BNC-2120 front panel to connect analog output
signals to your DAQ device.1The number of connectors you use depends on your DAQ device
and application. Refer to your DAQ device documentation for information about the use of these
signals.
1 When using the BNC-2120 with Connector 1 of two connector M/X Series devices, the AO <0..1> BNCs
on the BNC-2120 map to the AO <2..3> channels on the device.
RES+ AI 3
BNC-2120
VCC
User Resistor
AI 11
AI GND
AI SENSE
RES–
AI
Resistor Value VAI 3 VAI 11
–
VAI 11 10 kΩ()⁄
---------------------------------------=

BNC-2120 Installation Guide |© National Instruments |9
Using the Function Generator
The BNC-2120 has a function generator that produces sine or triangle waveforms and
TTL-compatible square waveforms. Use the switch below the Sine/Triangle BNC to select a sine
wave or triangle wave output for the connector. A TTL-compatible square wave is always
present at the TTL Square Wave BNC.
To adjust the frequency of the function generator, select your frequency range using the
Frequency Selection switch. You can select 0.1–10 kHz, 1–100 kHz, or 13–1000 kHz. The
Frequency Adjust knob adjusts the frequency within the preselected range for the sine or triangle
wave and the TTL square wave outputs.
The Amplitude Adjust knob adjusts the amplitude of the sine or triangle wave output up to
4.4 Vp-p.
Connecting Timing I/O Signals
Connect the timing I/O signals of your DAQ device to the PFI 0/P1.0 (AI START TRIG) BNC
or the timing I/O screw terminals on the BNC-2120. When connecting signals to the screw
terminals, use 28–16 AWG wire with the insulation stripped to 0.28 in.
Table 2 describes the timing I/O BNC and terminal signals on the BNC-2120.
Table 2. BNC-2120 Timing I/O BNC/Terminal Descriptions
BNC/Terminal Description
PFI 0/P1.0 Programmable Function Interface channel 0 or Port 1 Digital
Input/Output channel 0
AI START TRIG (AI Start Trigger Signal)—As an output, this pin is the
ai/StartTrigger signal. In post-trigger DAQ sequences, a low-to-high
transition indicates the initiation of the acquisition sequence. In
applications with pre-trigger samples, a low-to-high transition indicates
the initiation of the pre-trigger samples.
PULSES Refer to the Using the Quadrature Encoder section for information
about using these terminals.
UP/DN
PFI 1/P1.1 Programmable Function Interface channel 1 or Port 1 Digital
Input/Output channel 1
AI REF TRIG (AI Reference Trigger Signal)—As an output, this pin is
the ai/ReferenceTrigger signal. In applications with pretrigger samples,
a low-to-high transition indicates the initiation of the post-trigger
samples. AI Reference Trigger
is not used in applications with posttrigger samples.

10 |ni.com |BNC-2120 Installation Guide
PFI 2/P1.2 Programmable Function Interface channel 2 or Port 1 Digital
Input/Output channel 2
AI CONV CLK (AI Convert Clock Signal)—As an output, this pin is the
ai/ConvertClock signal. A high-to-low edge on AI CONV indicates that
an A/D conversion is occurring.
PFI 3/P1.3 Programmable Function Interface channel 3 or Port 1 Digital
Input/Output channel 3
CTR 1 SOURCE (Counter 1 Source Signal)—As an output, this pin is
the Ctr1Source signal. This signal reflects the actual source connected to
the general-purpose counter 1.
PFI 4/P1.4 Programmable Function Interface channel 4 or Port 1 Digital
Input/Output channel 4
CTR 1 GATE (Counter 1 Gate Signal)—As an output, this pin is the
Ctr1Gate signal. This signal reflects the actual gate signal connected to
the general-purpose counter 1.
PFI 5/P1.5 Programmable Function Interface channel 5 or Port 1 Digital
Input/Output channel 5
AO SAMP CLK (AO Sample Clock Signal)—As an output, this pin is
the ao/SampleClock signal. A high-to-low edge on AO SAMP indicates
that the AO primary group is being updated.
PFI 6/P1.6 Programmable Function Interface channel 6 or Port 1 Digital
Input/Output channel 6
AO START TRIG (AO Start Trigger Signal)—As an output, this pin is
the ao/StartTrigger signal. In timed AO sequences, a low-to-high
transition indicates the initiation of the waveform generation.
PFI 7/P1.7 Programmable Function Interface channel 7 or Port 1 Digital
Input/Output channel 7
AI SAMP CLK (AI Sample Clock Signal)—As an output, this pin is the
ai/SampleClock signal. This pin pulses once at the start of each AI
sample in the interval sample. A low-to-high transition indicates the start
of the sample.
Table 2. BNC-2120 Timing I/O BNC/Terminal Descriptions (Continued)
BNC/Terminal Description