Strain- and Bridge-Based Measurements
NI USB-9237
• Full-, half-, and quarter-bridge (120/350 Ω) completion1 • 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)
1Quarter
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
1Quarter
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 (ƒs) ................................. (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
Error1 Percent of Reading Percent of Range2 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 signal1 Negative excitation signal1 TEDS DATA TEDS Return1 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 Vrms, verified by a 5 s dielectric withstand test
– 1 2 3 4 5 6 7 8 –
SC AI+ AIRS+ RSEX+ EXT+ TSC
These signals are shared by all four RJ50 connectors on the USB-9237.
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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
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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
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*351510A-01*
351510A-01 2007-9107-301-101-D
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