Strain- and Bridge-Based Measurements
NI USB-9237
• Full-, half-, and quarter-bridge
(120/350
Ω)
completion
1
• Bus powered
• Built-in excitation up to 10 V
• Up to 50 kS/s/ch sample rate
• Simultaneous acquisition with
four ADCs
• Quick sensor connect with
RJ50 connectors
• TEDS (IEEE 1454.1) compatible
• External excitation input through analog
bridge (optional)
1
Quarter
Compatible Software
•
•
•
•
•
•
LabVIEW
LabWindows
™
/CVI
Measurement Studio
Visual Basic 6.0
C# and Visual Basic .NET
ANSI C/C++
Measurement Services
Software (included)
• NI-DAQmx driver software
• Measurement & Automation Explorer
configuration utility
• LabVIEW SignalExpress LE
data-logging software
bridge requires accessory.
Operating Systems
• Windows Vista/XP/2000
Overview
The National Instruments USB-9237 combines performance and
portability by making the NI 9237 C Series module compatible with the
bus-powered USB carrier for C Series modules. This module is ideal for
laptop applications because the USB port on the laptop powers all
acquisition and sensor excitation.
Connectivity
The USB-9237 uses four standard RJ50 connectors for rapid sensor
connection. You can add an RJ50 connector to any sensor using a
crimping tool, making sensor removal and insertion as easy as
connecting a PC to a network. For screw-terminal connectivity, the
NI 9949 accessory kit converts from RJ50 to 10 screw terminals. RJ50
cable kits are available in quantities of four 2 m cables and one 10 m
cable. For custom sensor wiring, cable kits are available with an RJ50
connector on one end and 10 signal wires on the other.
High-Speed Measurements
The NI USB-9237 module can take measurements at up to 50 kS/s on
four channels simultaneously and continuously stream the data back
over a Hi-Speed USB interface to serve applications from static load
or fatigue testing to high-speed fracture tests.
Software
The USB-9237 is shipped with the standard NI-DAQmx bundle that
includes Measurement & Automation Explorer (MAX) for configuration
and testing; LabVIEW SignalExpress LE for out-of-the-box measurements,
logging, and data display; and an API/driver for languages such as
LabVIEW, ANSI C, C#, Visual Basic .NET, Visual Basic 6.0, Measurement
Studio, and LabWindows/CVI.
Sensor Compatibility
With full-, half-, and quarter-bridge completion, the USB-9237 can
measure a variety of load, force, and torque cells as well as some
pressure transducers and most strain gages.
1
Safety Isolation
• 30 V of overvoltage protection
• 60 V of CAT I channel-to-earth ground isolation
• 1000 V of transient withstand isolation
1
Quarter
bridge requires accessory.
Strain- and Bridge-Based Measurements
Specifications
>>
For complete specifications, see the
NI USB-9237 User Guide and
Excitation Voltages
Although the sensor industry does not recognize a single standard
excitation voltage level, excitation voltage levels of between 2.5 and
10 V are common. You can program the USB-9237 to supply 2.5, 3.3,
5, 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
USB-9237 automatically reduces internal excitation voltages as needed
to stay below 150 mW.
The power consumed by a single bridge is
Specifications
manual at
ni.com/manuals.
Input Characteristics
Internal
External
24 bits
Delta-sigma
(with analog prefiltering)
Sampling mode............................... Simultaneous
Data rates (ƒ
s
) ................................. (50 kS/s)/n, n= 1, 1, …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
Overvoltage protection
between any two terminals ........... ±30 V
Accuracy
Error
1
Percent of Reading
Percent of Range
2
Calibrated max (-40 to 70 °C)
0.20%
0.25%
Calibrated typ (25 °C, ±5 °C)
0.05%
0.05%
Uncalibrated max (-40 to 70 °C)
0.60%
0.35%
Uncalibrated typ (25 °C, ±5 °C)
0.20%
0.1%
1
Excluding offset null or shunt calibration.
2
Range equals 25 mV/V.
Number of channels............................
Bridge completion
Full and half ....................................
Quarter............................................
ADC resolution................................
Type of ADC ....................................
4
V
ex
---------
-
R
2
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.
With the 150 mW limit, you can 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 USB-9237.
Gain drift .............................................
Offset drift
2.5 V excitation...............................
3.3 V excitation...............................
5 V excitation..................................
10 V excitation................................
10 ppm/°C max
0.6
μV/V
per °C
0.5
μV/V
per °C
0.3
μV/V
per °C
0.2
μV/V
per °C
Channel Signal Names
RJ50 (10p10c) Modular Plug and RJ50 RJ45 Signal
Receptacle Pin Numbers
Pin Pin Name
1
2
3
4
5
6
7
8
9
10
1
Signal Description
Shunt calibration
Positive input signal
Negative input signal
Positive remote sense signal
Negative remote sense signal
Positive excitation signal
1
Negative excitation signal
1
TEDS DATA
TEDS Return
1
Shunt calibration
Safety
Safety Voltages
Connect only voltages that are within these limits.
Between any two terminals ............... ±30 V max
Isolation
Channel-to-channel............................. No isolation between channels
Channel-to-earth ground
Continuous...................................... 60 VDC, Measurement Category I
Withstand ....................................... 1,000 V
rms
, verified by a 5 s
dielectric withstand test
–
1
2
3
4
5
6
7
8
–
SC
AI+
AI-
RS+
RS-
EX+
EX-
T+
T-
SC
These signals are shared by all four RJ50 connectors on the USB-9237.
BUY ONLINE
at
ni.com
or
CALL 800 813 3693 (U.S.)
2
Strain- and Bridge-Based Measurements
Accessories
There are several options for connecting signals to the USB-9237, as
shown in figures 1 and 2.
Ordering Information
NI USB-9237 (carrier, module, and USB cable) ....................780137-01
NI 9945 (1/4 bridge, 350
Ω,
qty 4) ......................................194739-01
NI 9944 (1/4 bridge, 120
Ω,
qty 4) ......................................194738-01
NI 9949 (RJ50 to screw terminal) ........................................196809-01
NI 9942 (excitation connector) ..............................................194611-01
RJ50 cable, 2 m (qty 4)..........................................................194612-02
RJ50 cable, 10 m (qty 1)........................................................194612-10
RJ50 to signal wire cable, 2 m (qty 4) ..................................195950-02
RJ50 to signal wire cable, 10 m (qty 1) ................................195950-10
BUY NOW!
For complete product specifications, pricing, and accessory
information, call 800 813 3693 (U.S.) or go to
ni.com/compactdaq.
Figure 1. NI 9237 with RJ50 to 10 m Signal Wire Cable
Figure 2. NI 9237 with RJ50 Cable and Screw-Terminal Accessories
BUY ONLINE
at
ni.com
or
CALL 800 813 3693 (U.S.)
3
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ni.com
• 800 813 3693
National Instruments • info@ni.com
*351510A-01*
351510A-01
2007-9107-301-101-D
© 2007 National Instruments Corporation. All rights reserved. CVI, LabVIEW, Measurement Studio, National Instruments, National Instruments Alliance Partner, NI, ni.com, SCXI, and
SignalExpress are trademarks of National Instruments. The mark LabWindows is used under a license from Microsoft Corporation. Other product and company names listed are
trademarks or trade names of their respective companies. A National Instruments Alliance Partner is a business entity independent from National Instruments and has no agency,
partnership, or joint-venture relationship with National Instruments.
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