8-Channel Strain Gage Modules
NI 9235, NI 9236
• 8 channels, simultaneous quarter-bridge inputs • 10 kS/s/ch sample rate • 1000 Vrms transient isolation • 24-bit resolution • Multiple module synchronization within the same chassis • Ability to program for USB with the easy-to-use NI-DAQmx driver • Built-in excitation • Built-in shunt calibration
Recommended Software
• LabVIEW • LabWindows™/CVI • Measurement Studio
NI-DAQmx Compatible Software
• LabVIEW SignalExpress • Visual Studio .NET • ANSI C/C++/C#
Connectivity
• NI 9235/9236 modules are shipped with everything needed to connect signals out of the box • Backshell is available for added strain relief and cable protection
C Series Compatibility
• NI CompactDAQ (NI-DAQmx) • CompactRIO (NI-RIO) • R Series expansion chassis (NI-RIO)
Module NI 9237 NI 9235 NI 9236
C Series Compatibility CompactRIO, NI CompactDAQ, USB, Wi-Fi CompactRIO, NI CompactDAQ, USB Carrier CompactRIO, NI CompactDAQ, USB Carrier
Channels 4 8 8
Resolution 24 bits 24 bits 24 bits
Excitation Up to 10 V or external 2.0 V 3.3 V
Bridge Completion Full, half, quarter (120, 350 Ω) Quarter (120 Ω) Quarter (350 Ω)
Sample Rate (kS/s/ch) 50 10 10
Simultaneous
Table 1. NI C Series Strain Gage Module Selection Guide
Overview and Applications
NI 9235 and 9236 C Series analog input modules are ideal for mediumto high-channel-count strain measurement applications such as structural or impact test. You can use these modules in the 8-slot NI CompactDAQ USB chassis for a plug-and-play, portable setup that can measure up to 64 channels in a single chassis. All channels of all C Series modules synchronize in the backplane. For structural health monitoring or other applications that require embedded logging or processing, you can use NI 9235/9236 modules in 4- and 8-slot NI CompactRIO chassis, which include an onboard processor and storage media. CompactRIO has an extended operational temperature range as well as rugged shock and vibration specifications and a Class 1, Division 2 hazardous location rating. The small size and high performance of C Series hardware make it a good choice for compact test systems with multiple measurement types. You can add and synchronize new measurements by installing additional modules in the chassis. Common systems that use strain gages range from small engine test cells to mountain bike frame tests to in-vehicle chassis and suspension tests. The high bandwidth available in C Series hardware like NI CompactDAQ and CompactRIO delivers highspeed measurements such as dynamic strain, acceleration, and sound. You can mix these measurements with lower-speed measurements such as temperature in the same system with the same program.
High Throughput with Multiple ADCs
The use of multiple analog-to-digital converters (ADCs) in a single module has two main benefits. First, the overall sample rate available to each channel is dramatically increased. This is important when conducting high-speed tests, such as impact or fracture tests, over multiple channels. The other main advantage is the elimination of phase offset between channels when sampling at higher speeds.
Elimination of Unwanted Signals with Built-In Antialias Filters
For dynamic measurements, it is important to filter out unwanted signals. Without some form of filtering, unwanted high-frequency signals can alias the signal you are measuring, causing incorrect readings. To prevent these phenomena, NI 9235/9236 modules have built-in antialiasing filters that adjust to your selected sample rate and ensure that the signal you are measuring has no interference from signals beyond the Nyquist frequency.
Mixed-Measurement Test System
NI 9235/9236 modules are just two in a collection of more than 50 C Series modules for measurements such as temperature, acceleration, voltage, current, sound, pressure, load, force, torque, and digital I/O. You can easily synchronize every C Series module you use in a chassis to acquire data from all channels at the same rate and at the same time.
8-Channel Strain Gage Modules
NI CompactRIO Platform
When used with the small, rugged CompactRIO embedded control and data acquisition system, C Series analog input modules connect directly to reconfigurable I/O (RIO) field-programmable gate array (FPGA) hardware to create high-performance embedded systems. The reconfigurable FPGA hardware within CompactRIO provides a variety of options for custom timing, triggering, synchronization, filtering, signal processing, and highspeed decision making for all C Series analog input modules. For instance, with CompactRIO, you can implement custom triggering for any analog sensor type on a per-channel basis using the flexibility and performance of the FPGA and the numerous arithmetic and comparison function blocks built into the NI LabVIEW FPGA Module.
Accessories
NI 9235/9236 modules are shipped with everything you need to take them out of the box and begin connecting signal wires. For added strain relief, you can purchase connector backshells as an accessory kit. Accessory kits are also available for spares or replacements of spring terminal connectors for the modules.
Backshell for NI 9235/9236 Strain Gage Modules
C Series Chassis
NI CompactDAQ Platform
NI CompactDAQ delivers the simplicity of USB to sensor and electrical measurements on the benchtop, in the field, and on the production line. By combining the ease of use and low cost of a data logger with the performance and flexibility of modular instrumentation, NI CompactDAQ offers fast, accurate measurements in a small, simple, and affordable system. Flexible software options make it easy to use NI CompactDAQ to log data for simple experiments or to develop a fully automated test or control system. The modular design can measure up to 256 channels of electrical, physical, mechanical, or acoustical signals in a single system. In addition, per-channel ADCs and individually isolated modules ensure fast, accurate, and safe measurements.
Ordering Information
NI 9235 (120 Ω) ....................................................................779993-01 NI 9236 (350 Ω) ....................................................................779994-01 NI 9965 strain relief backshell..............................................780216-01 NI 9966 replacement connector............................................780542-01
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For complete product specifications, pricing, and accessory information, call 800 813 3693 (U.S.) or go to ni.com/compactrio.
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8-Channel Strain Gage Modules
Stability, NI 9236
Gain drift ............................................. 6 ppm/°C Offset drift........................................... 1.7 µV/V/°C
Specifications
The following specifications are typical for the range -40 to 70 °C unless otherwise noted. The specifications are the same for the NI 9235 and the NI 9236 unless otherwise noted.
Dynamic Characteristics
Channel-to-Channel Matching (Calibrated)
Input Signal Frequency (fin) 0 to 1 kHz 0 to 4 kHz Gain Typical 0.08% 0.17% Maximum 0.11% 0.32% Phase Maximum 0.34°/kHz · fin
Input Characteristics
120 Ω, 10 ppm/°C max 350 Ω, 10 ppm/°C max 24 bits Delta-sigma (with analog prefiltering) Sampling mode ................................... Simultaneous Internal master timebase ( fM) Frequency........................................ 12.8 MHz Accuracy ......................................... ±100 ppm max Data rate range ( fs) using internal master timebase Minimum......................................... 794 S/s Maximum........................................ 10 kS/s Data rate range ( fs) using external master timebase Minimum......................................... 195.3125 S/s Maximum........................................ 10.547 kS/s fM ÷ 256 , n = {2, 4, 5, ..., 63} Data rates ( fs) ..................................... n Full-scale range................................... ±29.4 mV/V (+62,500 µε/-55,500 µε) Scaling coefficient .............................. 3.5062 nV/V per LSB Overvoltage protection between any two terminals ........... ±30 V Number of channels............................ Quarter-bridge completion NI 9235 ........................................... NI 9236 ........................................... ADC resolution.................................... Type of ADC ........................................ 8 analog input channels
Accuracy, NI 9235
Measurement Conditions Calibrated typ (25 °C, ±5 °C) Calibrated max (-40 to 70 °C) Uncalibrated typ (25 °C, ±5 °C) Uncalibrated max (-40 to 70 °C) Percent of Reading1 (Gain Error) 0.02% 0.07% 0.15% 0.53% Percent of Range†, ‡ (Offset Error) 30 Days after 1 Year after Cal. (±5 °C) Cal. (±5 °C) 0.1% 0.17% 1.25% 2.14% 0.15% 0.4%
1Exclusive of lead wire desensitization error. † Range equals 29.4 mV/V. ‡ Calibrated errors represent offset stability following unstrained measurement. Errors include the effect of completion resistor tolerance and drift.
Stability, NI 9235
Gain drift ............................................. 6 ppm/°C Offset drift........................................... 2.2 µV/V/°C
Phase nonlinearity fin = 0 to 1 kHz ................................ fin = 0 to 4 kHz ................................ Input delay ......................................... Passband Frequency........................................ Flatness (fs = 10 kS/s)..................... Stopband Frequency........................................ Rejection......................................... Alias-free bandwidth .......................... Oversample rate.................................. Rejection at oversample rate (fs = 10 kS/s) ................................... Input noise fs = 1 kS/s NI 9235 ....................................... NI 9236 ....................................... fs = 10 kS/s NI 9235 ....................................... NI 9236 ....................................... SFDR (1 kHz, -60 dBFS) NI 9235 ........................................... NI 9236 ........................................... THD (1 kHz, -20 dBFS) NI 9235 ........................................... NI 9236 ........................................... Crosstalk (fin = 1 kHz).......................... Common-mode voltage, all signals to earth ground.................. CMRR (fin = 0 to 60 Hz) NI 9235 ........................................... NI 9236 ........................................... MTBF ...................................................
±0.002° ±0.1° 38.2/fs + 11 µs 0.45 · fs 33 mdB max 0.55 · fs 100 dB 0.45 · fs 64 · fs 80 dB at 640 kHz
0.38 µV/Vrms 0.25 µV/Vrms 0.85 µV/Vrms 0.5 µV/Vrms 110 dB 115 dB -90 dB -95 dB -100 dB ±60 VDC 120 dB 110 dB 566,796 hours at 25 °C; Bellcore Issue 2, Method 1, Case 3, Limited Part Stress Method
Accuracy, NI 9236
Measurement Conditions Calibrated typ (25 °C, ±5 °C) Calibrated max (-40 to 70 °C) Uncalibrated typ (25 °C, ±5 °C) Uncalibrated max (-40 to 70 °C)
1Exclusive
Percent of Reading1 (Gain Error) 0.02% 0.07% 0.15% 0.53%
Percent of Range†, ‡ (Offset Error) 30 Days after 1 Year after Cal. (±5 °C) Cal. (±5 °C) 0.08% 0.16% 0.79% 1.67% 0.14% 0.39%
Note: Contact NI for Bellcore MTBF specifications at other temperatures or for MIL-HDBK-217F specifications.
Shunt Calibration Characteristics
Shunt calibration accuracy
Measurement Conditions Typical (25 °C, ±5 °C) Maximum (-40 to 70 °C) NI 9235 Percent of Reading (Gain Error) 0.09% 0.22% NI 9236 Percent of Reading (Gain Error) 0.07% 0.2%
of lead wire desensitization error. † Range equals 29.4 mV/V. ‡ Calibrated errors represent offset stability following unstrained measurement. Errors include the effect of completion resistor tolerance and drift.
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8-Channel Strain Gage Modules
Resistance NI 9235 ........................................... NI 9236 ........................................... Output value NI 9235 ........................................... NI 9236 ........................................... Temperature drift ............................... Method................................................
50 kΩ 100 kΩ -599.28 µV/V -873.47 µV/V 15 ppm/°C Shunt across completion resistor Constant voltage 2.0 V ± 1% 3.3 V ± 1% 80 mA 46 mA
Excitation Characteristics
Excitation type .................................... Excitation value NI 9235 ........................................... NI 9236 ........................................... Maximum output current NI 9235 ........................................... NI 9236 ...........................................
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