National Instruments NI 9233 User manual

OPERATING INSTRUCTIONS AND SPECIFICATIONS
NI 9233
4-Channel, ±5 V, 24-Bit IEPE Analog Input Module
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NI 9233 Operating Instructions and Specifications 2 ni.com
This document describes how to use the National Instruments 9233
and includes specifications and connector assignments for the
NI 9233. Visit ni.com/info and enter rdsoftwareversion to
determine which software youneed for the modules youare using.
For information about installing, configuring, and programming
the system, refer to the system documentation. Visit ni.com/info
and enter cseriesdoc for information about C Series
documentation.
Note The safety guidelines and specifications in this
document are specific to the NI 9233. The other
components in the system might not meet the same safety
ratings and specifications. Refer to the documentation for
each component in the system to determine the safety
ratings and specifications for the entire system. Visit
ni.com/info and enter cseriesdoc for information
about C Series documentation.

© National Instruments Corp. 3 NI 9233 Operating Instructions and Specifications
Safety Guidelines
Operate the NI 9233 only as described in these operating
instructions.
Hot Surface This icon denotes that the component may be
hot. Touching this component may result in bodily injury.
Safety Guidelines for Hazardous Locations
The NI 9233 is suitable for use in Class I, Division 2, Groups A, B,
C, D, T4 hazardous locations; Class I, Zone 2, AEx nC IIC T4, and
Ex nC IIC T4 hazardous locations; and nonhazardous locations
only. Follow these guidelines if youare installing the NI 9233 in a
potentially explosive environment. Not following these guidelines
may result in serious injury or death.
Caution Do not disconnect I/O-side wires or connectors
unless power has been switched off or the area is known
to be nonhazardous.
Caution Do not remove modules unless power has been
switched off or the area is known to be nonhazardous.

NI 9233 Operating Instructions and Specifications 4 ni.com
Caution Substitution of components may impair
suitability for Class I, Division 2.
Caution For Zone 2 applications, install the system
in an enclosure rated to at least IP 54 as defined by
IEC 60529 and EN 60529.
Caution For Zone 2 applications, connected signals must
be within the following limit:
Capacitance .......................... 0.2 μF max
Special Conditions for Hazardous Locations Use in Europe
This equipment has been evaluated as EEx nC IIC T4 equipment
under DEMKO Certificate No. 03 ATEX 0324020X. Each module
is marked II 3G and is suitable for use in Zone 2 hazardous
locations. If youare using the NI 9233 in Gas Group IIC hazardous
locations or in ambient temperatures of –40 °C ≤Ta ≤70 °C, you
must use the device in an NI chassis that has been evaluated as
EEx nC IIC T4, Ex nA IIC T4, or Ex nL IIC T4 equipment.

© National Instruments Corp. 5 NI 9233 Operating Instructions and Specifications
Special Conditions for Marine Applications
Some modules are Lloyd’s Register (LR) Type Approved for
marine applications. To verify Lloyd’s Register certification, visit
ni.com/certification and search for the LR certificate, or
look for the Lloyd’s Register mark on the module.
Caution To meet radio frequency emission requirements
for marine applications, use shielded cables and install
the system in a metal enclosure. Suppression ferrites
must be installed on power supply inputs near power
entries to modules and controllers. Power supply and
module cables must be separated on opposite sides of the
enclosure and must enter and exit through opposing
enclosure walls.

NI 9233 Operating Instructions and Specifications 6 ni.com
Connecting the NI 9233
The NI 9233 has four BNC connectors that provide connections for
four simultaneously sampled analog input channels.
Figure 1. NI 9233 Connector Assignments
AI3+
AI3–
AI2+
AI2–
AI0+
AI0–
AI1+
AI1–

© National Instruments Corp. 7 NI 9233 Operating Instructions and Specifications
Each channel has a BNC connector to which youcan connect an
Integrated Electronic Piezoelectric (IEPE) sensor. The center pin
of the connector, AI+, provides the DC excitation and the AC
signal connection. The shell of the connector, AI–, provides the
excitation return path and the AC signal ground reference.
Yo ucan connect ground-referenced or floating IEPE sensors to the
NI 9233. Youcan avoid picking up ground noise by using a floating
connection. Typical IEPE sensors have a case that is electrically
isolated from the IEPE electronics, so connecting the sensor to the
NI 9233 results in a floating connection even though the case of the
sensor is grounded. To further minimize ground noise, prevent
the metal shells of the BNC connectors from touching each other,
the modules, or the chassis.
If youmake a ground-referenced connection between the IEPE
sensor and the NI 9233, make sure the voltage on the AI– shell
is in the common-mode range to ensure proper operation of the
NI 9233. The AI– shell is protected against accidental contact
with overvoltages within the overvoltage protection range. Refer
to the Specifications section for more information about operating
voltages and overvoltage protection. Figures 2 and 3 illustrate
connecting grounded and floating IEPE sensors to the NI 9233.

NI 9233 Operating Instructions and Specifications 8 ni.com
Figure 2. Connecting a Grounded IEPE Sensor to the NI 9233
Figure 3. Connecting a Floating IEPE Sensor to the NI 9233
NI 9233
IEPE Sensor
AI+
AI–
+
–
NI 9233
+
–
AI–
AI+
IEPE Sensor

© National Instruments Corp. 9 NI 9233 Operating Instructions and Specifications
The NI 9233 analog input channels are referenced to the chassis
ground through a 50 Ωresistor. To minimize ground noise, make
sure that the chassis ground is connected to the earth ground. Each
channel is protected from overvoltages. The NI 9233 provides
an IEPE excitation current for each input signal. The signal is
AC-coupled, buffered, and conditioned. The signal is then sampled
by a 24-bit Delta-Sigma ADC. The NI 9233 IEPE excitation
current and AC coupling are always enabled. Refer to Figure 4 for
an illustration of the input circuitry for one channel of the NI 9233.
Figure 4. Input Circuitry for One Channel of the NI 9233
NI 9233
AI+
AI–
50 Ω
ADC
Amplifier
and
Prefilter
Excitation
Current
AC
Coupling
+

NI 9233 Operating Instructions and Specifications 10 ni.com
The NI 9233 also has TEDS circuitry. For more information about
TEDS, visit ni.com/info and enter rdteds.
Understanding NI 9233 Filtering
The NI 9233 uses a combination of analog and digital filtering
to provide an accurate representation of in-band 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 9233 represents signals within the passband, as quantified
primarily by passband flatness and phase nonlinearity. 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 respect to
frequency is called the passband flatness. The digital filters of the
NI 9233 adjust the frequency range of the passband to match the
data rate. Therefore, the amount of gain or attenuation at a given

© National Instruments Corp. 11 NI 9233 Operating Instructions and Specifications
frequency depends on the data rate. Figure 5 shows typical
passband flatness for data rates above 25.65 kS/s and less than
or equal to 25.65 kS/s.
Figure 5. Typical Passband Flatness for the NI 9233
Frequency/Data Rate
0.50.4
0.025
0.000
–0.025
–0.050
0.30.20.10
Gain (dB)
Data Rate
≤ 25.65 kS/s
Data Rate
>25.65 kS/s

NI 9233 Operating Instructions and Specifications 12 ni.com
The relative phases of these signals also have a
frequency-dependent delay. The variation in the phase delay with
frequency is called the phase nonlinearity. Figure 6 shows the
phase nonlinearity for data rates above 25.65 kS/s and less than or
equal to 25.65 kS/s. The phase nonlinearity scales directly with the
oversample rate, so the two curves normalize the signal frequency
to the data rate.

© National Instruments Corp. 13 NI 9233 Operating Instructions and Specifications
Figure 6. Phase Nonlinearity of the NI 9233
0.450.15
4
2
0
–2
–4
0.100.050.00 0.400.350.300.250.20
Data Rate
≤ 25.65 kS/s
Phase Error (Degrees)
Data Rate
>25.65 kS/s
Frequency/Data Rate

NI 9233 Operating Instructions and Specifications 14 ni.com
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 within the
stopband.
Alias-Free Bandwidth
Any signal that appears in the alias-free bandwidth of the NI 9233
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 it is equal to the data
rate minus the stopband frequency.
Understanding NI 9233 Data Rates
The frequency of a master timebase (fM) controls the data rate (fs)
of the NI 9233. The NI 9233 includes an internal master timebase
with a frequency of 12.8 MHz, but the module also can accept an
external master timebase or export its own master timebase. To
synchronize the data rate of an NI 9233 with other modules that use
master timebases to control sampling, all of the modules must

© National Instruments Corp. 15 NI 9233 Operating Instructions and Specifications
share a single master timebase source. Refer to the software help
for information about configuring the master timebase source for
the NI 9233. Visit ni.com/info and enter cseriesdoc for
information about C Series documentation.
The following equations provide the available data rates of the
NI 9233:
When fsis ≤25.65 kS/s, fs=
where nis any integer from 2 to 25.
When fsis > 25.65 kS/s, fs=
where nis any integer from 2 to 3.
However, the data rate must remain within the appropriate data rate
range. Refer to the Specifications section for more information
about the data rate range. When using the internal master timebase
of 12.8 MHz, the result is data rates of 50 kS/s, 33.33 kS/s, 25 kS/s,
and so on down to 2.0 kS/s, depending on the value of n. When
using an external timebase with a frequency other than 12.8 MHz,
the NI 9233 has a different set of data rates.
f
M256÷
n
---------------------
f
M128÷
n
---------------------

NI 9233 Operating Instructions and Specifications 16 ni.com
Note The cRIO-9151 R Series Expansion chassis does
not support sharing timebases between modules.
Sleep Mode
This module supports a low-power sleep mode. Support for sleep
mode at the system level depends on the chassis that the module is
plugged into. Refer to the chassis manual for information about
support for sleep mode. If the chassis supports sleep mode, refer to
the software help for information about enabling sleep mode. Visit
ni.com/info and enter cseriesdoc for information about
C Series documentation.
Typically, when a system is in sleep mode, youcannot
communicate with the modules. In sleep mode, the system
consumes minimal power and may dissipate less heat than it does
in normal mode. Refer to the Specifications section for more
information about power consumption and thermal dissipation.

© National Instruments Corp. 17 NI 9233 Operating Instructions and Specifications
Specifications
The following specifications are typical for the range –40 to 70 °C
unless otherwise noted.
Input Characteristics
Number of channels .......................... 4 analog input channels
ADC resolution ................................. 24 bits
Type of ADC..................................... 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.................................... 2.0 kS/s
Maximum ................................... 50 kS/s
Data rate range (fs) using external master timebase
Minimum.................................... 2.0 kS/s
Maximum ................................... 51.3 kS/s

NI 9233 Operating Instructions and Specifications 18 ni.com
Data rates1(fs)
fs≤25.65 kS/s............................. , n = 2, 3, ..., 25
fs> 25.65 kS/s ............................ , n = 2, 3
Input coupling................................... AC
AC cutoff frequency
–3 dB .......................................... 0.5 Hz typ
–0.1 dB ....................................... 4.2 Hz max
1 The data rate must remain within the appropriate data rate range. Refer to the
Understanding NI 9233 Data Rates section for more information.
f
M256÷
n
---------------------
f
M128÷
n
---------------------

© National Instruments Corp. 19 NI 9233 Operating Instructions and Specifications
AC cutoff frequency response
Input range ........................................ ±5 V
AC voltage full-scale range
Minimum.................................... ±5 Vpk
Typical ........................................ ±5.4 Vpk
Maximum ................................... ±5.8 Vpk
Frequency (Hz)
104
0.5
0.0
–0.5
–1.0
321098765
Gain (dB)

NI 9233 Operating Instructions and Specifications 20 ni.com
Common-mode voltage range
(AI– to earth ground) ........................ ±2 V max
IEPE excitation current
Minimum.................................... 2.0 mA
Typical ........................................ 2.2 mA
IEPE compliance voltage.................. 19 V max
Use the following equation to make sure that your configuration
meets the IEPE compliance voltage range.
Vcommon-mode + Vbias ±Vfull-scale must be 0 to 19.
where Vcommon-mode is any common-mode voltage applied to
the NI 9233,
Vbias is the bias voltage of the accelerometer, and
Vfull-scale is the full-scale voltage of the accelerometer.