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
C Series Compatibility
• NI CompactDAQ (NI-DAQmx)
• CompactRIO (NI-RIO)
• R Series expansion chassis (NI-RIO)
Module
NI 9237
NI 9235
NI 9236
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
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
3
3
3
Table 1. NI C Series Strain Gage Module Selection Guide
Overview and Applications
High Throughput with Multiple ADCs
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.
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
Accessories
NI CompactRIO Platform
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.
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.
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
BUY NOW!
For complete product specifications, pricing, and accessory
information, call 800 813 3693 (U.S.) or go to ni.com/compactrio.
BUY ONLINE at ni.com or CALL 800 813 3693 (U.S.)
2
8-Channel Strain Gage Modules
Stability, NI 9236
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.
Number of channels............................
Quarter-bridge completion
NI 9235 ...........................................
NI 9236 ...........................................
ADC resolution....................................
Type of ADC ........................................
8 analog input channels
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
Accuracy, NI 9235
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%
0.15%
0.4%
1.25%
2.14%
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
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)
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%
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.
1Exclusive
Dynamic Characteristics
Channel-to-Channel Matching (Calibrated)
Input Characteristics
Measurement Conditions
Gain drift ............................................. 6 ppm/°C
Offset drift........................................... 1.7 µV/V/°C
0.14%
0.39%
0.79%
1.67%
Input Signal
Frequency (fin)
0 to 1 kHz
0 to 4 kHz
Gain
Typical
0.08%
0.17%
Phase
Maximum
Maximum
0.11%
0.32%
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 ...................................................
0.34°/kHz · fin
±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
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)
NI 9236 Percent of Reading
(Gain Error)
0.09%
0.22%
0.07%
0.2%
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3
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
Excitation Characteristics
Excitation type ....................................
Excitation value
NI 9235 ...........................................
NI 9236 ...........................................
Maximum output current
NI 9235 ...........................................
NI 9236 ...........................................
Constant voltage
2.0 V ± 1%
3.3 V ± 1%
80 mA
46 mA
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2008-9862-301-101-D
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