National Instruments NI USB-9234 User manual

USER GUIDE AND SPECIFICATIONS
NI USB-9234
4-Channel, ±5 V, 24-Bit Software-Selectable IEPE and AC/DC
Analog Input Module
This user guide describes how to use the National Instruments USB-9234
and includes device specifications and connector assignments.
Introduction
The NI USB-9234 consists of two components: an NI 9234 module and an
NI USB-9162 carrier, as shown in Figure 1.
Figure 1. NI USB-9234 Components
NI 9234
NI USB-9162
NI USB-9234
HI-Speed USB Carrier
NI USB-9162
Hi-Speed USB Carrier
NI USB-9162

NI USB-9234 User Guide and Specifications 2 ni.com
Dimensions
Figure 2 shows the NI USB-9234 device dimensions.
Figure 2. NI USB-9234 Device in Millimeters (Inches)
Safety Guidelines
Operate the NI USB-9234 only as described in this user guide.
Note Although the NI 9234 module may have more stringent certification standards than
the NI USB-9234, when used with the NI USB-9162 carrier, the combined system may be
limited. Refer to the Specifications section for more details.
Hot Surface This icon denotes that the component may be hot. Touching this component
may result in bodily injury.
Caution Do not disconnect I/O-side wires or connectors unless power has been switched
off or the area is known to be nonhazardous.
Caution Do not the remove module unless power has been switched off or the area is
known to be nonhazardous.
Caution The NI USB-9234 is not certified for use in hazardous locations.
Hi-Speed USB Carrier
NI USB-9162
140.66 mm
(5.538 in.)
138.30 mm
(5.445 in.)
120.68 mm
(4.751 in.)
118.26 mm
(4.656 in.)
88.12 mm
(3.469 in.)
25.34 mm
(0.998 in.)

©National Instruments Corporation 3 NI USB-9234 User Guide and Specifications
Safety Guidelines for Hazardous Voltages
If hazardous voltages are connected to the module, take the following
precautions. A hazardous voltage is a voltage greater than 42.4 Vpk or
60 VDC to earth ground.
Caution Ensure that hazardous voltage wiring is performed only by qualified personnel
adhering to local electrical standards.
Caution Do not mix hazardous voltage circuits and human-accessible circuits on the same
module.
Caution Make sure that devices and circuits connected to the module are properly
insulated from human contact.
Related Documentation
Each application software package and driver includes information about
writing applications for taking measurements and controlling measurement
devices. The following references to documents assume you have
NI-DAQmx 8.8 or later, and where applicable, version 7.1 or later
of the NI application software.
NI-DAQmx for Windows
The DAQ Getting Started Guide describes how to install your NI-DAQmx
for Windows software, your NI-DAQmx-supported DAQ device, and how
to confirm that your device is operating properly. Select Start»All
Programs»National Instruments»NI-DAQ»DAQ Getting Started
Guide.
The NI-DAQ Readme lists which devices are supported by this version of
NI-DAQmx. Select Start»All Programs»National Instruments»
NI-DAQ»NI-DAQ Readme.
The NI-DAQmx Help contains general information about measurement
concepts, key NI-DAQmx concepts, and common applications that are
applicable to all programming environments. Select Start»All
Programs»National Instruments»NI-DAQ»NI-DAQmx Help.

NI USB-9234 User Guide and Specifications 4 ni.com
LabVIEW
If you are a new user, use the Getting Started with LabVIEW manual to
familiarize yourself with the LabVIEW graphical programming
environment and the basic LabVIEW features you use to build data
acquisition and instrument control applications. Open the Getting Started
with LabVIEW manual by selecting Start»All Programs»National
Instruments»LabVIEW»LabVIEW Manuals or by navigating to the
labview\manuals directory and opening LV_Getting_Started.pdf.
Use the LabVIEW Help, available by selecting Help»Search the
LabVIEW Help in LabVIEW, to access information about LabVIEW
programming concepts, step-by-step instructions for using LabVIEW, and
reference information about LabVIEW VIs, functions, palettes, menus, and
tools. Refer to the following locations on the Contents tab of the LabVIEW
Help for information about NI-DAQmx:
•Getting Started»Getting Started with DAQ—Includes overview
information and a tutorial to learn how to take an NI-DAQmx
measurement in LabVIEW using the DAQ Assistant.
•VI and Function Reference»Measurement I/O VIs and
Functions—Describes the LabVIEW NI-DAQmx VIs and properties.
•Taking Measurements—Contains the conceptual and how-to
information you need to acquire and analyze measurement data in
LabVIEW, including common measurements, measurement
fundamentals, NI-DAQmx key concepts, and device considerations.
LabWindows/CVI
The Data Acquisition book of the LabWindows/CVI Help contains
measurement concepts for NI-DAQmx. This book also contains Taking an
NI-DAQmx Measurement in LabWindows/CVI, which includes
step-by-step instructions about creating a measurement task using the DAQ
Assistant. In LabWindows™/CVI™, select Help»Contents, then select
Using LabWindows/CVI»Data Acquisition.
The NI-DAQmx Library book of the LabWindows/CVI Help contains API
overviews and function reference for NI-DAQmx. Select Library
Reference»NI-DAQmx Library in the LabWindows/CVI Help.

©National Instruments Corporation 5 NI USB-9234 User Guide and Specifications
Measurement Studio
If you program your NI-DAQmx-supported device in Measurement Studio
using Visual C++, Visual C#, or Visual Basic .NET, you can interactively
create channels and tasks by launching the DAQ Assistant from MAX or
from within Visual Studio .NET. You can generate the configuration code
based on your task or channel in Measurement Studio. Refer to the DAQ
Assistant Help for additional information about generating code. You also
can create channels and tasks, and write your own applications in your
ADE using the NI-DAQmx API.
For help with NI-DAQmx methods and properties, refer to the NI-DAQmx
.NET Class Library or the NI-DAQmx Visual C++ Class Library included
in the NI Measurement Studio Help. For general help with programming in
Measurement Studio, refer to the NI Measurement Studio Help, which is
fully integrated with the Microsoft Visual Studio .NET help. To view
this help file in Visual Studio. NET, select Measurement Studio»
NI Measurement Studio Help.
To create an application in Visual C++, Visual C#, or Visual Basic .NET,
follow these general steps:
1. In Visual Studio .NET, select File»New»Project to launch the New
Project dialog box.
2. Find the Measurement Studio folder for the language you want to
create a program in.
3. Choose a project type. You add DAQ tasks as a part of this step.
ANSI C without NI Application Software
The NI-DAQmx Help contains API overviews and general information
about measurement concepts. Select Start»All Programs»National
Instruments»NI-DAQ»NI-DAQmx Help.
The NI-DAQmx C Reference Help describes the NI-DAQmx Library
functions, which you can use with National Instruments data acquisition
devices to develop instrumentation, acquisition, and control applications.
Select Start»All Programs»National Instruments»NI-DAQ»
NI-DAQmx C Reference Help.

NI USB-9234 User Guide and Specifications 6 ni.com
.NET Languages without NI Application Software
With the Microsoft .NET Framework version 1.1 or later, you can use
NI-DAQmx to create applications using Visual C# and Visual Basic
.NET without Measurement Studio. You need Microsoft Visual Studio
.NET 2003 or Microsoft Visual Studio 2005 for the API documentation
to be installed.
The installed documentation contains the NI-DAQmx API overview,
measurement tasks and concepts, and function reference. This help is
fully integrated into the Visual Studio .NET documentation. To view the
NI-DAQmx .NET documentation, go to Start»All Programs»National
Instruments»NI-DAQ»NI-DAQmx .NET Reference Help. Expand
NI Measurement Studio Help»NI Measurement Studio .NET Class
Library»Reference to view the function reference. Expand
NI Measurement Studio Help»NI Measurement Studio .NET Class
Library»Using the Measurement Studio .NET Class Libraries to view
conceptual topics for using NI-DAQmx with Visual C# and Visual
Basic .NET.
To get to the same help topics from within Visual Studio, go to
Help»Contents. Select Measurement Studio from the Filtered By
drop-down list and follow the previous instructions.
Device Documentation and Specifications
Documentation for supported devices and accessories, including PDF
and help files describing device terminals, specifications, features, and
operation are on the NI-DAQmx CD that includes Device Documentation.
Insert the CD, open the Device Documentation directory, and double-click
the Device Documents shortcut for your language to find, view, and print
device documents.
Note You can also download these documents at ni.com/manuals.
Training Courses
If you need more help getting started developing an application with
NI products, NI offers training courses. To enroll in a course or obtain
a detailed course outline, refer to ni.com/training.
Technical Support on the Web
For additional support, refer to ni.com/support or zone.ni.com.

©National Instruments Corporation 7 NI USB-9234 User Guide and Specifications
Installing the Software
Software support for the NI USB-9234 for Windows Vista/XP/2000 is
provided by NI-DAQmx. The DAQ Getting Started Guide, which you can
download at ni.com/manuals, offers NI-DAQmx users step-by-step
instructions for installing software and hardware, configuring channels and
tasks, and getting started developing an application.
Installing Other Software
If you are using other software, refer to the installation instructions that
accompany your software.
Example Programs
The NI-DAQmx CD contains example programs that you can use to get
started programming with the NI USB-9234. Refer to the NI-DAQmx for
USB Devices Getting Started Guide that shipped with your device, which
is also accessible from Start»All Programs»National Instruments»
NI-DAQ for more information.
Installing the NI USB-9234 Device
Before installing the device, you must install the software you plan to use
with the device. Refer to the Installing the Software section of this guide
and the documentation included with the software for more information.
Installing the NI 9234 in the NI USB-9162 Carrier
The NI 9234 module and NI USB-9162 carrier are packaged separately.
Refer to Figure 3, while completing the following assembly steps:
1. Make sure no signals are connected to the NI 9234 module and the
USB cable is not connected to the device.
2. Remove the protective cover from the 15-pin D-SUB connector.

NI USB-9234 User Guide and Specifications 8 ni.com
3. Align the I/O module with the carrier, as shown in Figure 3.
Figure 3. Module Installation
4. Squeeze the latches and insert the NI 9234 module into the
NI USB-9162 carrier.
5. Press firmly on the connector side of the NI 9234 module until the
latches lock the module into place, as shown in Figure 4.
Figure 4. Locking Module into Place
Hi-Speed USB Carrier
NI USB-9162
Hi-Speed USB Carrier
NI USB-9162

©National Instruments Corporation 9 NI USB-9234 User Guide and Specifications
Mounting the NI USB-9234
Threaded inserts are located in the NI USB-9234 for mounting it to a panel.
Refer to Figure 5 for the module dimensions.
Figure 5. Module Dimensions
Connecting the NI USB-9234 to a Computer
Plug one end of the USB cable into the NI USB-9234 and the other end into
an available USB port on the computer. Refer to the NI-DAQmx for USB
Devices Getting Started Guide that shipped with your device, which is also
accessible from Start»All Programs»National Instruments»NI-DAQ,
for more information.
Threaded Insert
M3 x 0.5
8.5 mm (0.34 in.) Max Depth
72.2 mm
(2.84 in.)
85.7 mm
(3.37 in.)
76.1 mm
(3.00 in.)

NI USB-9234 User Guide and Specifications 10 ni.com
LED Indicator
The NI USB-9234 device has a green LED next to the USB connector.
The LED indicator indicates device status, as listed in Table 1. When the
device is connected to a USB port, the LED blinks steadily to indicate that
the device is initialized and is receiving power from the connection.
If your device is not blinking, make sure your computer has the latest
version of NI-DAQmx installed on it, and that the computer is not in
standby mode.
Table 1. LED State/Device Status
LED State Device Status
Not lit Device not connected or in suspend.
On, not blinking Device connected, but no module installed.
Single-blink Operating normally.
Double-blink Connected to USB Full-Speed port. Device performance
might be affected. Refer to the Specifications section for more
information.
Quadruple-blink Device error. Refer to ni.com/support.

©National Instruments Corporation 11 NI USB-9234 User Guide and Specifications
Wiring the NI USB-9234
The NI USB-9234 has four BNC connectors that provide connections to
four simultaneously sampled analog input channels. Each channel has a
BNC connector to which you can connect a signal source. You can also
enable excitation current on a per-channel basis to connect Integrated
Electronic Piezoelectric (IEPE) sensors. The center pin of the connector,
AI+, provides the DC signal connection. The shell of the connector, AI–,
provides the excitation return path and AC signal ground reference. Refer
to Figure 6 for the connector assignments for each channel.
Figure 6. NI USB-9234 Connector Assignments
AI3+
AI3–
AI2+
AI2–
AI0+
AI0–
AI1+
AI1–

NI USB-9234 User Guide and Specifications 12 ni.com
Connecting Signal Sources to the NI USB-9234
You can connect ground-referenced or floating signal sensors to the
NI USB-9234. To avoid picking up ground noise, use a floating
connection. To further minimize ground noise, prevent the metal shells of
the BNC connectors from touching each other, the modules, or the chassis.
If you make a ground-referenced connection between the signal source and
the NI USB-9234, make sure the voltage on the AI– shell is in the
common-mode range to ensure proper operation of the NI USB-9234. The
AI– shell is protected against accidental contact with overvoltages within
the overvoltage protection range. Refer to the Specifications section for
more information about operating voltages and overvoltage protection.
Figures 7 and 8 illustrate connecting grounded and floating signal sources
to the NI USB-9234.
Figure 7. Connecting a Grounded IEPE Sensor to the NI USB-9234
Figure 8. Connecting a Floating IEPE Sensor to the NI USB-9234
The NI USB-9234 can also provide an IEPE excitation current for each
channel to measure ground referenced or floating IEPE sensors. Typical
IEPE sensors have a case that is electrically isolated from the IEPE
electronics, so connecting the sensor to the NI USB-9234 results in a
floating connection even though the case of the sensor is grounded.
NI USB-9234
AI+
AI–
+
–
Signal
Source
Common-
Mode
Voltage
NI USB-9234
AI+
AI–
+
–
Signal
Source

©National Instruments Corporation 13 NI USB-9234 User Guide and Specifications
NI USB-9234 Circuitry
The NI USB-9234 analog input channels are referenced to chassis ground
through a 50 Ωresistor. To minimize ground noise, make sure that the
chassis ground is connected to earth ground. Each channel is protected
from overvoltages. You can configure the NI USB-9234 for AC or DC
coupling for each channel. You can turn the IEPE excitation current on or
off in AC-coupled mode (in software). IEPE current is not available in
DC-coupled mode. The input signal on each channel is buffered,
conditioned, and then sampled by a 24-bit, Delta-Sigma ADC.
Figure 9. Input Circuitry for One Channel
The NI USB-9234 uses common-mode bias current to bias the
current-limiting diodes when IEPE current is turned off. When using
grounded signal sources, this current causes an error that is dependent on
the AI– lead impedance. This error is approximately 50 ppm of range and
15 ppm of reading per Ωof AI– impedance. The common-mode bias
current causes an error only with grounded sources and is not an issue with
floating signal sources. For best accuracy, use a floating connection or use
low-impedance leads when connecting grounded signal sources.
Figure 10. Measurement Error Introduced by Common-Mode Bias Current
2 mA IEPE On/Off
AI+
AI–
Amplifier
and
Prefilter
ADC
+
–
AC/DC Coupling
NI USB-9234
Common-
Mode
Bias
Current
Current-
Limiting
Diodes
50 Ω
NI USB-9234
AI+
AI–
+
–
Signal
Source
AI– Lead
Impedance
Common-
Mode
Bias
Current

NI USB-9234 User Guide and Specifications 14 ni.com
The NI USB-9234 also has TEDS circuitry. For more information about
TEDS, go to ni.com/info and enter rdteds.
Understanding NI USB-9234 Filtering
The NI USB-9234 uses a combination of analog and digital filtering
to provide an accurate representation of in-band signals while rejecting
out-of-band signals. The filters discriminate between signals based on the
frequency range, or bandwidth, of the signal. The three important
bandwidths to consider are the passband, the stopband, and the alias-free
bandwidth.
The NI USB-9234 represents signals within the passband as quantified
primarily by passband flatness and phase nonlinearity. The filters reject
frequencies within the stopband as much as possible, as quantified by
stopband rejection. All signals that appear in the alias-free bandwidth are
either unaliased signals or signals that have been filtered by at least the
amount of the stopband rejection.
Passband
The signals within the passband have frequency-dependent gain or
attenuation. The small amount of variation in gain with frequency is called
the passband flatness. The digital filters of the NI USB-9234 adjust the
frequency range of the passband to match the data rate. Therefore, the
amount of gain or attenuation at a given frequency depends on the data rate.
Figure 11 shows typical passband flatness for 51.2 kS/s data rate.
Figure 11. NI USB-9234 Typical Passband Response
Frequency (kHz)
302520
0.025
0.000
–0.025
–0.050 151050
Gain (dB)

©National Instruments Corporation 15 NI USB-9234 User Guide and Specifications
Stopband
The filter significantly attenuates all signals above the stopband frequency.
The primary goal of the filter is to prevent aliasing. Therefore, the stopband
frequency scales precisely with the data rate. The stopband rejection is the
minimum amount of attenuation applied by the filter to all signals with
frequencies within the stopband.
Alias-Free Bandwidth
Any signal that appears in the alias-free bandwidth of the NI USB-9234 is
not an aliased artifact of signals at a higher frequency. The alias-free
bandwidth is defined by the ability of the filter to reject frequencies above
the stopband frequency, and it is equal to the data rate minus the stopband
frequency.
Understanding NI USB-9234 Data Rates
The frequency of a master timebase (fM) controls the data rate (fs) of the
NI USB-9234. The NI USB-9234 includes an internal master timebase
with a frequency of 13.1072 MHz, but the module also can accept an
external master timebase or export its own master timebase. Refer to the
software help for information about configuring the master timebase source
for the NI USB-9234.
The following equation provides the available data rates of the
NI USB-9234:
fs=
where nis any integer from 1 to 31.
The data rate must remain within the data range. Refer to the Specifications
section for more information about the data rate range. When using the
internal master timebase of 13.1072 MHz, the result is data rates of
51.2 kS/s, 25.6 kS/s, 17.067 kS/s, and so on down to 1.652 kS/s, depending
on the value of n. When using an external timebase with a frequency other
than 13.1072 MHz, the NI USB-9234 has a different set of data rates.
fM
(
)256÷
n
-
------------------------

NI USB-9234 User Guide and Specifications 16 ni.com
Specifications
The following specifications are typical for the range 0 to 60 °C unless
otherwise noted.
Input Characteristics
Number of channels................................4 analog input channels
ADC resolution.......................................24 bits
Type of ADC ..........................................Delta-Sigma
(with analog prefiltering)
Sampling mode .......................................Simultaneous
Type of TEDS supported ........................IEEE.1451.4 TEDS Class I
(interface)
Internal master timebase (fM)
Frequency ........................................13.1072 MHz
Accuracy..........................................±50 ppm max
Data rate range (fs) using internal master timebase
Minimum .........................................1.652 kS/s
Maximum ........................................51.2 kS/s
Data rate range (fs) using external master timebase
Minimum .........................................0.391 kS/s
Maximum ........................................52.734 kS/s
Data rates (fs) .......................................... , n= 1, 2, …, 31
Input coupling.........................................AC/DC (software-selectable)
AC cutoff frequency
–3 dB ...............................................0.5 Hz typ
–0.1 dB ............................................4.6 Hz max
f
M256÷
n
--------------------

©National Instruments Corporation 17 NI USB-9234 User Guide and Specifications
AC cutoff frequency response
Input range ............................................. ±5 V
AC voltage full-scale range
Minimum ........................................ ±5 Vpk
Typical ............................................ ±5.1 Vpk
Maximum........................................ ±5.2 Vpk
Common-mode voltage
(AI– to earth ground) ............................. ±2 V max
IEPE excitation current (software-selectable on/off)
Minimum ........................................ 2.0 mA
Typical ............................................ 2.1 mA
Power-on glitch ...................................... 90 mA for 10 ms
IEPE compliance voltage ....................... 19 V max
If you are using an IEPE sensor, use the following equation to make sure
that your configuration meets the IEPE compliance voltage range.
must be 0 to 19
where Vcommon-mode is the common-mode voltage of the
NI USB-9234,
Vbias is the bias voltage of the IEPE sensor,
Vfull-scale is the full-scale voltage of IEPE sensor
104
0.5
0.0
–0.5
–1.0 321098765
Gain (dB)
Frequency (Hz)
Vcommon mode–Vbias Vfull scale– ++

NI USB-9234 User Guide and Specifications 18 ni.com
Overvoltage protection (with respect to chassis ground)
For a signal source connected
to AI+ and AI– ................................±30 V
For a low-impedance source
connected to AI+ and AI– ...............–6 to 30 V
Input delay ..............................................3.2 ms + 38.4 fs
Accuracy1
Gain drift
Typical.............................................0.14 mdB/°C (16 ppm/°C)
Maximum ........................................0.45 mdB/°C (52 ppm/°C)
Offset drift
Typical.............................................19.2 mV/°C
Maximum ........................................118 mV/°C
Channel-to-channel matching
Gain
Typical......................................0.01 dB
Maximum .................................0.04 dB
Phase ( fin in kHz) ............................fin · 0.045° + 0.04 max
Passband
Frequency ........................................0.45 · fs
Flatness (fs= 51.2 kS/s)...................±40 mdB
(pk-to-pk max)
1 Refer to the NI USB-9234 Circuitry section for information regarding grounded signal sources and measurement accuracy.
Measurement Conditions
Percent of Reading
(Gain Error)
Percent of Range*
(Offset Error)
Calibrated max (–40 to 70 °C) 0.34%,
±0.03 dB
±0.14%,
7.1 mV
Calibrated typ (25 °C ±5 °C) 0.05%,
±0.005 dB
±0.006%,
0.3 mV
Uncalibrated max (–40 to 70 °C) 1.9%,
±0.16 dB
±0.27%,
13.9 mV
Uncalibrated typ (25 °C ±5 °C) 0.48%,
±0.04 dB
±0.04%,
2.3 mV
*Range = 5.1 Vpk

©National Instruments Corporation 19 NI USB-9234 User Guide and Specifications
Phase nonlinearity
(fs= 51.2 kS/s) ................................ ±0.45° max
Stopband
Frequency........................................ 0.55 · fs
Rejection ......................................... 100 dB
Alias-free bandwidth.............................. 0.45 · fs
Oversample rate ..................................... 64 · fs
Crosstalk (1 kHz) ................................... –110 dB
CMRR (fin ≤1 kHz)
Minimum ........................................ 40 dB
Typical ............................................ 47 dB
SFDR (fin = 1 kHz, –60 dBFS) .............. 120 dB
Idle channel noise and noise density
Input impedance
Differential...................................... 305 kΩ
AI– (shield) to chassis ground ........ 50 Ω
Total harmonic distortion (THD)
Intermodulation distortion (–1 dBFS)
DIN 250 Hz/8 kHz
4:1 amplitude ratio .......................... –80 dB
CCIF 11 kHz/12 kHz
1:1 amplitude ratio .......................... –93 dB
Idle Channel 51.2 kS/s 25.6 kS/s 2.048 kS/s
Noise 97 dBFS 99 dBFS 103 dBFS
50 μVrms 40 μVrms 25 μVrms
Noise density 310 nV/√Hz 350 nV/√Hz 780 nV/√Hz
Input
Amplitude
1 kHz,
–40 to 70 °C
8 kHz,
–40 to 70 °C
–1 dBFS –95 dB –87 dB
–20 dBFS –95 dB –80 dB