National Instruments Computer Accessories NI USB 9237 User Manual

USER GUIDE AND SPECIFICATIONS  
NI USB-9237  
4-Channel, 24-Bit Half/Full-Bridge Analog Input Device  
This user guide describes how to use the National Instruments USB-9237  
and lists the device specifications. The NI USB-9237 provides a USB  
interface for four channels of 24-bit half/full-bridge analog input.  
Introduction  
The NI USB-9237 consists of two components: an NI 9237 module and an  
NI USB-9162 carrier, as shown in Figure 1.  
NI 9237  
H i -  
S p e e d  
N
I
U S  
B
- 9 1  
U S B C a r r i e r  
6 2  
NI USB-9162  
H i - S  
N
P
I
e e d U S B  
U
S B  
- 9 1  
6 2  
C a r r i e  
r
NI USB-9237  
Figure 1. NI USB-9237 Components  
 
 
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 8.7 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-DAQ. 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.  
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.  
© National Instruments Corporation  
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NI USB-9237 User Guide and Specifications  
 
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.  
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.  
NI USB-9237 User Guide and Specifications  
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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»NationalInstruments»NI-DAQ»  
NI-DAQmx C Reference Help.  
.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»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  
NI-DAQmx includes the Device Document Browser, which contains  
online documentation for supported DAQ, SCXI, and switch devices, such  
as help files describing device pinouts, features, and operation, and PDF  
files of the printed device documents. You can find, view, and/or print the  
documents for each device using the Device Document Browser at any  
time by inserting the CD. After installing the Device Document Browser,  
device documents are accessible from Start»All Programs»National  
Instruments»NI-DAQ»Browse Device Documentation.  
Note You can download these documents at ni.com/manuals.  
© National Instruments Corporation  
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NI USB-9237 User Guide and Specifications  
 
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.  
Installing the Software  
Software support for the NI USB-9237 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-9237. Refer to the NI-DAQmx for  
USB Devices Getting Started Guide that shipped with your device, and is  
also accessible from Start»All Programs»National Instruments»  
NI-DAQ, for more information.  
Installing the NI USB-9237 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 9237 in the USB-9162 Carrier  
The NI 9237 module and USB-9162 carrier are packaged separately. Refer  
to Figure 3, while completing the following assembly steps:  
1. Make sure that no signals are connected to the NI 9237 module and the  
USB cable is not connected to the device.  
2. Remove the protective cover from the 15-pin D-SUB connector.  
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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 9237 module into the USB-9162  
carrier.  
5. Press firmly on the connector side of the NI 9237 module until the  
latches lock the module into place, as shown in Figure 4.  
Figure 4. Locking Module into Place  
© National Instruments Corporation  
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NI USB-9237 User Guide and Specifications  
 
   
Mounting the NI USB-9237 to a Panel  
Threaded inserts are located in the NI USB-9237 for mounting it to a panel.  
Refer to Figure 5 for dimensions.  
85.7 mm  
(3.37 in.)  
72.2 mm  
(2.84 in.)  
Threaded Insert  
M3 x 0.5  
8.5 mm (0.34 in.) Max Depth  
76.1 mm  
(3.00 in.)  
Figure 5. Module Dimensions in Millimeters (Inches)  
Connecting the NI USB-9237 to a Computer  
Plug one end of the USB cable into the NI USB-9237 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, and is also  
accessible from Start»All Programs»National Instruments»NI-DAQ,  
for more information.  
LED Indicator  
The NI USB-9237 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 the LED is not blinking, it may mean that the device is not initialized or  
the computer is in standby mode. In order for the device to be recognized,  
the device must be connected to a computer that has NI-DAQmx installed  
on it. If your device is not blinking, make sure your computer has the latest  
version of NI-DAQmx installed on it, and the computer is not in standby  
mode.  
NI USB-9237 User Guide and Specifications  
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Table 1. LED State/Device Status  
LED State  
Not lit  
Device Status  
Device not connected or in suspend.  
Device connected, but no module installed.  
Operating normally.  
On, not blinking  
Single-blink  
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.  
Wiring the NI USB-9237 Device  
The NI USB-9237 has four RJ-50 receptacles that provide connections for  
four half or full bridges. Table 2 lists the signal names of the terminals for  
each connector, and shows the correlation between the pin numbers of  
the RJ-50 10-position/10-conductor (10p10c) modular plug and the  
NI USB-9237 receptacle. The NI USB-9237 also has a four-position  
connector you can use to connect an external excitation voltage source to  
the module. Table 2 lists the connections between an external excitation  
voltage source and the NI USB-9237.  
Note For a list of accessories available for use with the NI USB-9237, refer to  
ni.com/info, and enter info code rd9237.  
© National Instruments Corporation  
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NI USB-9237 User Guide and Specifications  
 
 
Table 2. Terminal Assignments  
RJ-50 (10p10c)  
Modular Plug  
and Receptacle  
Pin Numbers  
Signal  
Name  
Signal  
Description  
RJ-50 Pin  
RJ-45 Pin  
1
2
1
SC  
Shunt calibration  
AI+  
Positive input  
signal  
3
4
5
6
7
2
3
4
5
6
AI–  
RS+  
RS–  
EX+  
EX–  
Negative input  
signal  
Positive remote  
sense signal  
Negative remote  
sense signal  
Positive  
excitation signal*  
Negative  
excitation signal*  
8
9
7
8
T+  
T–  
SC  
TEDS data  
TEDS return*  
Shunt calibration  
10  
* These signals are shared by all four RJ-50 connectors on the NI USB-9237.  
Caution National Instruments does not recommend using an RJ-45 with the NI USB-9237  
because it can physically damage pins 1 and 10 on the device, and thus permanently disable  
shunt calibration no matter what connector you use.  
NI USB-9237 User Guide and Specifications  
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3
4
2
1
1
EX–  
2
EX+  
3
EX+  
4
EX–  
Figure 6. Four Position External Excitation Voltage Source Connection  
Connecting Loads to the NI USB-9237  
Refer to Figure 7 for an illustration of how to connect full and half bridges  
to the NI USB-9237.  
RS+  
EX+  
AI+  
AI–*  
2
1
EX–  
RS–  
SC  
SC  
T+  
*When you connect a half bridge  
to the NI USB-9237, the AI– signal is  
not connected.  
TEDS  
T–  
1
The dotted line indicates that the full  
bridge is optional while the half bridge  
is required.  
2
These four signals are the only  
signals that must be connected.  
Figure 7. Half- and Full-Bridge Connections  
Note You can use a quarter bridge with the NI USB-9237 if you either add a resistor  
externally to create a half bridge or use the NI 9944 or NI 9945 Quarter Bridge Completion  
Accessory. Visit ni.com and search for the NI 9944 and/or NI 9945 Quarter Bridge  
© National Instruments Corporation  
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NI USB-9237 User Guide and Specifications  
 
   
Completion Accessories for more information about these accessories and how to purchase  
them.  
Wiring TEDS Channels  
Ensure that neither the TEDS data (T+) nor the TEDS return (T–) is tied in  
common to any AI signals on the NI USB-9237. Visit ni.com/info and  
enter the info code rdteds for information about TEDS sensors.  
NI USB-9237 Connection Options  
Wiring resistance can create errors in bridge circuits. The NI USB-9237  
provides two mechanisms to correct for these errors: remote sensing and  
shunt calibration.  
Remote Sensing  
Remote sensing continuously and automatically corrects for errors in  
excitation leads, and generally is most appropriate for full- and half-bridge  
sensors.  
Long wire and smaller gauge wire has greater resistance, which can result  
in gain error. The voltage drop caused by resistance in the wires connecting  
the excitation voltage to the bridge is a source of gain error.  
The NI USB-9237 includes remote sensing to compensate for this error.  
Remote sense wires are connected to the point where the excitation voltage  
wires connect to the bridge circuit.  
Figure 8 shows a diagram of how the NI USB-9237 uses remote sensing.  
RS +  
R
lead  
EX +  
R
R
R
AI –  
R
bridge  
bridge  
AI +  
bridge  
bridge  
EX –  
RS –  
R
lead  
Figure 8. Remote Sensor Error Compensation  
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As shown in Figure 8, the actual bridge excitation voltage is smaller than  
the voltage at the EX+ and EX– leads. If remote sensing of the actual bridge  
voltage is not used, the resulting gain error is  
2Rlead  
------------------  
Rbridge  
for full-bridge sensors, and  
Rlead  
------------------  
Rbridge  
for half-bridge sensors.  
If the remote sense (RS) signals are connected directly to the bridge resistors,  
the NI USB-9237 senses the actual bridge voltage sense and eliminates the  
gain errors caused by the resistance of the EX+ and EX– leads.  
Shunt Calibration  
Shunt calibration can correct for errors from the resistance of both the  
excitation wiring and wiring in the individual resistors of the bridge. Shunt  
calibration is most useful with quarter-bridge sensors because there may be  
significant resistance in the wiring to the active resistor in the bridge.  
The NI USB-9237 shunt calibration circuitry consists of a precision  
100 kΩ resistor and a software-controlled switch. You can leave the shunt  
calibration terminals connected to the sensor, and then apply or remove the  
shunt calibration resistance in software.  
While remote sensing corrects for resistances from the EX terminals on the  
NI USB-9237 to the sensor, shunt calibration corrects for these errors and  
for errors caused by wire resistance within an arm of the bridge.  
Shunt calibration involves simulating the input of strain by changing the  
resistance of an arm in the bridge by some known amount. This is  
accomplished by shunting, or connecting, a large resistor of known value  
across one arm of the bridge, creating a known strain-induced change in  
resistance. The output of the bridge can then be measured and compared to  
the expected voltage value. The results are used to correct gain errors in the  
entire measurement path, or to simply verify general operation to gain  
confidence in the setup.  
A stable signal, which is typically the unloaded state of the sensor, is used  
first with the shunt calibration switch off and then again with the switch on.  
The difference in these two measurements provides an indication of the  
gain errors from wiring resistances. You can design the software  
application to correct subsequent readings for this gain error.  
© National Instruments Corporation  
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NI USB-9237 User Guide and Specifications  
 
Excitation Voltages  
Although the sensor industry does not recognize a single standard excitation  
voltage level, excitation voltage levels of between 2.5 V and 10 V are  
common. You can program the NI USB-9237 to supply 2.5 V, 3.3 V, 5 V,  
or 10 V of excitation voltage, and the module can provide up to 150 mW of  
excitation power. Unless you supply external excitation voltage, National  
Instruments recommends that you set the excitation voltage to a value that  
keeps the total power below 150 mW. The NI USB-9237 automatically  
reduces internal excitation voltages as needed to stay below 150 mW.  
The power consumed by a single bridge is  
2
Vex  
------------  
R
where R is the total resistance of the bridge.  
For a full bridge, R is equal to the resistance of each element. For a half or  
quarter bridge, R is equal to two times the resistance of each element.  
The 150 mW limit allows you to power full and half bridges as follows:  
Four 350 Ω half bridges at 5.0 V  
Four 350 Ω full bridges at 3.3 V  
Four 120 Ω half bridges at 2.5 V  
If you need an excitation voltage greater than 150 mW, use the  
four-position external excitation voltage connector to connect an external  
excitation source to the NI USB-9237. Refer to Figure 6 for an illustration  
and pinout description of the four-position external excitation voltage  
connector.  
NI USB-9237 Circuitry  
The NI USB-9237 is isolated from earth ground. However, the individual  
channels are not isolated from each other. The EX+, EX–, and T– signals  
are common among all channels. You can connect the NI USB-9237 to a  
device that is biased at any voltage within the NI USB-9237 rejection range  
of earth ground. Refer to the Specifications section for more information.  
You also can connect floating signals to the NI USB-9237. If you connect  
floating signals to the NI USB-9237, National Instruments recommends  
you connect the EX– signal to the earth ground or shield for better noise  
rejection.  
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Each channel on the NI USB-9237 has an independent 24-bit ADC and  
input amplifier that enable you to sample signals from all four channels  
simultaneously.  
The NI USB-9237 also includes filters to prevent aliasing. The filters on the  
NI USB-9237 filter according to the sampling rate.  
Understanding NI USB-9237 Filtering  
The NI USB-9237 uses a combination of analog and digital filtering to  
provide an accurate representation of desirable 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-9237 represents signals within the passband as accurately  
as possible, 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 filters of the NI USB-9237 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 9 shows  
typical passband flatness for a range of data rates.  
0.025  
0.000  
–0.025  
–0.050  
0
0.2  
0.4  
0.6  
0.8  
1
Frequency/Sample Rate (kHz)  
Figure 9. Typical Passband Response  
© National Instruments Corporation  
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NI USB-9237 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 that would be aliased into the alias-free bandwidth.  
Alias-Free Bandwidth  
Any signal that appears in the alias-free bandwidth of the NI USB-9237  
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 equals the data rate minus the stopband  
frequency.  
Specifications  
The following specifications are typical for the range 0 to 60 °C unless  
otherwise noted.  
Input Characteristics  
Number of channels................................4  
Bridge completion  
Full and half.....................................Internal  
Quarter.............................................External  
ADC resolution.......................................24 bits  
Type of ADC ..........................................Delta-sigma (with analog  
prefiltering)  
Sampling mode.......................................Simultaneous  
50.000 kS/s  
n
--------------------------------  
Data rates (fs) .........................................  
, n = 1, 2, ... 31  
Master timebase (internal)  
Frequency ........................................12.8 MHz  
Accuracy.......................................... 100 ppm max  
Nominal full-scale range ........................ 25 mV/V  
Scaling coefficient ..................................2.9802 nV/V per LSB  
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Overvoltage protection  
between any two terminals..................... 30 V  
Accuracy  
Percent of Reading  
Percent of Range  
(Offset Error)†  
Error*  
(Gain Error)  
Calibrated max (0 to 60 °C)  
Calibrated typ (25 °C, 5 °C)  
Uncalibrated max (0 to 60 °C)  
Uncalibrated typ (25 °C, 5 °C)  
0.20%  
0.25%  
0.05%  
0.35%  
0.1%  
0.05%  
0.60%  
0.20  
* Excluding offset null or shunt calibration.  
† Range equals 25 mV/V.  
Gain drift................................................ 10 ppm/°C max  
Offset drift  
2.5 V excitation............................... 0.6 μV/V per °C  
3.3 V excitation............................... 0.5 μV/V per °C  
5 V excitation.................................. 0.3 μV/V per °C  
10 V excitation................................ 0.2 mV/V per °C  
Channel-to-channel matching (calibrated)  
Gain  
Phase  
Input Signal Frequency  
(fin)  
Typical  
0.15%  
0.4%  
Maximum  
0.3%  
Maximum  
0 to 1 kHz  
1 to 20 kHz  
* fin is in kHz.  
0.125°/kHz · fin*  
1.1%  
Phase nonlinerarity  
0 to 1 kHz........................................ <0.001°  
0 to 20 kHz...................................... 0.1°  
Input delay.............................................. 4.8 μs + 38.4/fs  
Passband  
Frequency........................................ 0.45 · fs  
Flatness ........................................... 0.1 dB max  
© National Instruments Corporation  
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NI USB-9237 User Guide and Specifications  
 
Stopband  
Frequency ........................................0.55 · fs  
Rejection..........................................100 dB  
Alias-free bandwidth ..............................0.45 · fs  
Oversample rate......................................64 · fs  
Rejection at oversample rate1  
50 kS/s......................................90 dB @ 3.2 MHz  
10 kS/s......................................60 dB @ 640 kHz  
Common-mode voltage  
All signals to earth ground .............. 60 VDC  
Common-mode rejection ratio (CMRR)  
Relative to earth ground2.................140 dB @ 0 to 60 Hz  
Relative to EX– ...............................85 dB @ 0 to 1 kH  
Input noise  
Density  
(nV/Vrms per  
1Hz)  
Total  
(50 kS/S)  
(μV/Vrms  
Excitation  
Voltage  
0 to 1 kHz  
)
(nV/Vrms  
)
2.5 V  
3.3 V  
5 V  
8
6
4
2
1.3  
250  
1.0  
190  
0.6  
130  
10 V  
0.3  
65  
Spurious-free dynamic  
range (SFDR)..........................................106 dB,  
(1 KHz, –60 dBFS)  
Total harmonic distortion (fundamental @ –20 dBFS)  
1 kHz ...............................................100 dB  
8 kHz ...............................................90 dB  
Excitation noise ......................................0.1 mV/Vrms  
1
2
Rejection by analog prefilter of signal frequencies at oversample rate.  
Measured with a balanced cable. Shielded cables may be significantly unbalanced.  
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Crosstalk  
1 kHz............................................... 110 dB  
10 kHz............................................. 100 dB  
Shunt calibration  
Resistance ....................................... 100 kΩ  
Resistor accuracy  
25 °C........................................ 110 Ω  
0 to 60 °C................................. 200 Ω  
Excitation  
Internal voltage ............................... 2.5 V, 3.3 V, 5.0 V, 10.0 V  
Internal power................................. 150 mW max  
External voltage .............................. 2 V to 10 V  
Power Requirements  
Current consumption from USB ............ 500 mA, max  
Suspend mode................................. 2.5 mA, max  
Bus Interface  
USB specification................................... USB 2.0 Hi-Speed  
Physical Characteristics  
Dimensions............................................. 12.1 cm × 8.6 cm × 2.5 cm  
(4.75 in. × 3.37 in. × 0.99 in.)  
Weight.................................................... Approx. 250 g (8.8 oz)  
Safety  
If you need to clean the module, wipe it with a dry towel.  
Safety Voltages  
Connect only voltages that are within these limits.  
Between any two terminals.................... 30 V max  
© National Instruments Corporation  
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NI USB-9237 User Guide and Specifications  
 
Isolation  
Channel-to-channel..........................No isolation between channels  
Channel-to-earth ground  
Continuous ...............................60 VDC,  
Measurement Category I  
Withstand .................................1,000 Vrms, verified by a 5 s  
dielectric withstand test  
Measurement Category I is for measurements performed on circuits not  
directly connected to the electrical distribution system referred to as  
MAINS voltage. MAINS is a hazardous live electrical supply system that  
powers equipment. This category is for measurements of voltages from  
specially protected secondary circuits. Such voltage measurements include  
signal levels, special equipment, limited-energy parts of equipment,  
circuits powered by regulated low-voltage sources, and electronics. Do not  
connect the NI USB-9237 to signals or use for measurements within  
Measurement Categories II, III, or IV.  
Safety Standards  
The NI USB-9237 is designed to meet the requirements of the following  
standards of safety for electrical equipment for measurement, control,  
and laboratory use:  
IEC 61010-1, EN 61010-1  
UL 61010-1, CSA 612010-1  
Note For UL and other safety certifications, refer to the product label, or visit ni.com/  
certification, search by model number or product line, and click the appropriate link  
in the Certification column.  
Hazardous Locations  
The NI USB-9237 is not certified for use in hazardous locations.  
Environmental  
The NI USB-9237 device is intended for indoor use only.  
Operating temperature  
(IEC60068-2-1, IEC 60068-2-2) ............0 to 60 °C  
Storage temperature  
(IEC60068-2-1, IEC 60068-2-2) ............–40 to 85 °C  
Ingress protection ...................................IP 40  
NI USB-9237 User Guide and Specifications  
20  
ni.com  
 
Operating humidity  
(IEC 60068-2-56)................................... 10 to 90% RH,  
noncondensing  
Storage humidity  
(IEC 60068-2-56)................................... 5 to 95% RH,  
noncondensing  
Maximum altitude.................................. 2,000 m  
Pollution Degree (IEC 60664) ............... 2  
Electromagnetic Compatibility  
This product is designed to meet the requirements of the following  
standards of EMC for electrical equipment for measurement, control,  
and laboratory use:  
EN 61326 EMC requirements; Minimum Immunity  
EN 55011 Emissions; Group 1, Class A  
CE, C-Tick, ICES, and FCC Part 15 Emissions; Class A  
Note For EMC compliance, operate this device with double-shielded cables.  
CE Compliance  
This product meets the essential requirements of applicable European  
Directives, as amended for CE marking, as follows:  
2006/95/EC; Low-Voltage Directive (safety)  
2004/108/EC; Electromagnetic Compatibility Directive (EMC)  
Note Refer to the Declaration of Conformity (DoC) for this product for any additional  
regulatory compliance information. To obtain the DoC for this product, visit  
ni.com/certification, search by model number or product line, and click the  
appropriate link in the Certification column.  
© National Instruments Corporation  
21  
NI USB-9237 User Guide and Specifications  
 
Environmental Management  
National Instruments is committed to designing and manufacturing  
products in an environmentally responsible manner. NI recognizes that  
eliminating certain hazardous substances from our products is beneficial  
not only to the environment but also to NI customers.  
For additional environmental information, refer to the NI and the  
Environment Web page at ni.com/environment. This page contains the  
environmental regulations and directives with which NI complies, as well  
as other environmental information not included in this document.  
Waste Electrical and Electronic Equipment (WEEE)  
EU Customers At the end of their life cycle, all products must be sent to a WEEE recycling  
center. For more information about WEEE recycling centers and National Instruments  
WEEE initiatives, visit ni.com/environment/weee.htm.  
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National Instruments  
(RoHS)  
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RoHS  
ni.com/environment/rohs_china  
(For information about China RoHS compliance, go to  
.)  
Calibration  
You can obtain the calibration certificate for the NI USB-9237 at  
ni.com/calibration.  
Calibration interval.................................1 year  
NI USB-9237 User Guide and Specifications  
22  
ni.com  
 
Where to Go for Support  
The National Instruments Web site is your complete resource for technical  
support. At ni.com/support you have access to everything from  
troubleshooting and application development self-help resources to email  
and phone assistance from NI Application Engineers.  
National Instruments corporate headquarters is located at  
11500 North Mopac Expressway, Austin, Texas, 78759-3504.  
National Instruments also has offices located around the world to help  
address your support needs. For telephone support in the United States,  
create your service request at ni.com/support and follow the calling  
instructions or dial 512 795 8248. For telephone support outside the United  
States, contact your local branch office:  
Australia 1800 300 800, Austria 43 662 457990-0,  
Belgium 32 (0) 2 757 0020, Brazil 55 11 3262 3599,  
Canada 800 433 3488, China 86 21 5050 9800,  
Czech Republic 420 224 235 774, Denmark 45 45 76 26 00,  
Finland 358 (0) 9 725 72511, France 01 57 66 24 24,  
Germany 49 89 7413130, India 91 80 41190000, Israel 972 3 6393737,  
Italy 39 02 41309277, Japan 0120-527196, Korea 82 02 3451 3400,  
Lebanon 961 (0) 1 33 28 28, Malaysia 1800 887710,  
Mexico 01 800 010 0793, Netherlands 31 (0) 348 433 466,  
New Zealand 0800 553 322, Norway 47 (0) 66 90 76 60,  
Poland 48 22 3390150,Portugal 351 210 311 210,Russia 7 495 783 6851,  
Singapore 1800 226 5886, Slovenia 386 3 425 42 00,  
South Africa 27 0 11 805 8197, Spain 34 91 640 0085,  
Sweden 46 (0) 8 587 895 00, Switzerland 41 56 2005151,  
Taiwan 886 02 2377 2222, Thailand 662 278 6777,  
Turkey 90 212 279 3031, United Kingdom 44 (0) 1635 52354  
National Instruments, NI, ni.com, and LabVIEW are trademarks of National Instruments Corporation.  
Refer to the Terms of Use section on ni.com/legal for more information about National  
Instruments trademarks. Other 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.  
© 2007 National Instruments Corporation. All rights reserved.  
372306B-01  
Dec07  
 

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