NI 9227 User manual

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OPERATING INSTRUCTIONS AND SPECIFICATIONS
NI 9227
4-Channel, 5 Arms, 24-Bit, Simultaneous,
Channel-to-Channel Isolated Analog Input Module
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2|ni.com |NI 9227 Operating Instructions and Specifications
This document describes how to use the National Instruments 9225
and includes specifications and pin assignments for the NI 9225.
Note The safety guidelines and specifications in this
document are specific to the NI 9225. 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.
Related Information
Services
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NI CompactDAQ &
NI CompactRIO Documentation
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Chassis Compatibility
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Software Support
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NI 9227 Operating Instructions and Specifications |© National Instruments |3
Safety Guidelines
Operate the NI 9227 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.
Hazardous Voltage This icon denotes a warning
advising you to take precautions to avoid electrical
shock.
Caution Do not operate the NI 9242 in a manner not
specified in this manual. Product misuse can result in a
hazard. You can compromise the safety protection built
into the product if the product is damaged in any way. If
the product is damaged, return it to National Instruments
for repair.
Safety Guidelines for Hazardous Voltages
If hazardous voltages are connected to the module, take the
following precautions. A hazardous voltage is a voltage greater
than 42.4 Vpk or 60 VDC to earth ground.
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4|ni.com |NI 9227 Operating Instructions and Specifications
Caution Ensure that hazardous voltage wiring is
performed only by qualified personnel adhering to local
electrical standards.
Caution Do not mix hazardous voltage circuits and
human-accessible circuits on the same module.
Caution Make sure that devices and circuits connected
to the module are properly insulated from human contact.
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NI 9227 Operating Instructions and Specifications |© National Instruments |5
Caution When module terminals are hazardous voltage
LIVE (>42.4 Vpk/60 VDC), you must ensure that devices
and circuits connected to the module are properly
insulated from human contact. You must use the NI 9971
connector backshell kit to ensure that the terminals are
not accessible.
Figure 1 shows the NI 9971 connector backshell.
Figure 1. NI 9971 Connector Backshell
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6|ni.com |NI 9227 Operating Instructions and Specifications
Connecting the NI 9227
The NI 9227 has four 2-terminal detachable screw-terminal
connectors that provide connections for four simultaneously
sampled, isolated analog input channels.
Figure 2. NI 9227 Terminal Assignments
AI0+
AI0–
AI1+
AI1–
AI2+
AI2–
AI3+
AI3–
0
1
0
1
0
1
0
1
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NI 9227 Operating Instructions and Specifications |© National Instruments |7
You can connect ground-referenced or floating current sources to
the NI 9227. Connect the positive side of the current source to the
AI+ terminal, and connect the negative side of the current source
to the AI- terminal. If you make a ground-referenced connection
between the current source and the NI 9227, make sure the voltage
on the AI+ and AI- connections are in the channel-to-earth safety
voltage range to ensure proper operation of the NI 9227. Refer to
the Specifications section for more information about operating
voltages.
Note You must use 2-wire ferrules to create a secure
connection when connecting more than one wire to a
single terminal on the NI 9227.
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8|ni.com |NI 9227 Operating Instructions and Specifications
Refer to Figures 3 and 4 for illustrations of how to connect
grounded and floating current sources to the NI 9227.
Figure 3. Connecting a Grounded Current Source to the NI 9227
Figure 4. Connecting a Floating Current Source to the NI 9227
NI 9227
Current
Source
AI–
AI+
NI 9227
Current
Source
AI–
AI+
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NI 9227 Operating Instructions and Specifications |© National Instruments |9
The NI 9227 analog input channels are floating with respect to
earth ground and each other. The incoming analog signal on each
channel is conditioned, buffered, and then sampled by a 24-bit
Delta-Sigma ADC.
Each channel provides an independent signal path and ADC,
enabling you to sample all four channels simultaneously. Refer
to Figure 5 for an illustration of the circuitry for one channel of
the NI 9227.
Figure 5. Input Circuitry for One Channel of the NI 9227
NI 9227
AI+
AI–
ADC
Amplifier
Shunt
Resistor
Prefilter
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10 |ni.com |NI 9227 Operating Instructions and Specifications
Wiring for High-Vibration Applications
If an application is subject to high vibration, National Instruments
recommends that you either use ferrules to terminate wires to the
detachable screw-terminal connector or use the NI 9971 backshell
kit to protect the connections. Refer to Figure 6 for an illustration
of using ferrules. Refer to Figure 1 for an illustration of the
NI 9971 connector backshell.
Figure 6. 2-Terminal Detachable Screw-Terminal Connector with Ferrule
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NI 9227 Operating Instructions and Specifications |© National Instruments |11
Understanding NI 9227 Filtering
The NI 9227 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 9227 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 9227 adjust the frequency range of the passband to match the
data rate. Therefore, the amount of gain or attenuation at a given
frequency depends on the data rate. Figure 7 shows typical
passband flatness for the NI 9227.
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12 |ni.com |NI 9227 Operating Instructions and Specifications
Figure 7. Typical Passband Flatness for the NI 9227
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.
Frequency/DataRate (Hz)
0.50.4
0.025
0.000
–0.025
–0.050
0.30.20.10
Gain (dB)
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NI 9227 Operating Instructions and Specifications |© National Instruments |13
Alias-Free Bandwidth
Any signal that appears in the alias-free bandwidth of the NI 9227
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 9227 Data Rates
The frequency of a master timebase (fM) controls the data rate (fs)
of the NI 9227. The NI 9227 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 9227 with other modules that use
master timebases to control sampling, all of the modules must
share a single master timebase source. Refer to the software help
for information about configuring the master timebase source for
the NI 9227. Visit ni.com/info and enter cseriesdoc for
information about C Series documentation.
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14 |ni.com |NI 9227 Operating Instructions and Specifications
The following equation provides the available data rates of the
NI 9227:
fs=
where nis any integer from 1 to 31.
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, 25 kS/s,
16.667 kS/s, and so on down to 1.613 kS/s, depending on the value
of n. When using an external timebase with a frequency other than
12.8 MHz, the NI 9227 has a different set of data rates.
Note The NI cRIO-9151 R Series Expansion chassis
does not support sharing timebases between modules.
fM256÷
n
---------------------
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NI 9227 Operating Instructions and Specifications |© National Instruments |15
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, you cannot
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.
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16 |ni.com |NI 9227 Operating Instructions and Specifications
Specifications
The following specifications are typical for the range -40 to 70 °C
unless otherwise noted. All voltages are relative to the AI- signal
on each channel unless otherwise noted.
Caution The input terminals of this device are not
protected for electromagnetic interference. As a result,
this device may experience reduced measurement
accuracy or other temporary performance degradation
when connected cables are routed in an environment with
radiated or conducted radio frequency electromagnetic
interference. To limit radiated emissions and to ensure
that this device functions within specifications in its
operational electromagnetic environment, take
precautions when designing, selecting, and installing
measurement probes and cables.
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NI 9227 Operating Instructions and Specifications |© National Instruments |17
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.................................... 1.613 kS/s
Maximum ................................... 50 kS/s
Data rate range (fs) using external master timebase
Minimum.................................... 390.625 S/s
Maximum ................................... 51.36 kS/s
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18 |ni.com |NI 9227 Operating Instructions and Specifications
Data rates1(fs)................................... , n = 1, 2, ..., 31
Safe operating input range2, 3............ 5 Arms
Overcurrent handling4....................... 10 Arms for 1 s max
with 19 s minimum
cool down time at 5 Arms
Instantaneous measuring range5
Minimum.................................... 14.051 A peak
Typical ........................................ 14.977 A peak, at 23 ±5 °C
Typical scaling coefficient ................ 1.785397 μA/LSB
Input coupling................................... DC
1 The data rate must remain within the appropriate data rate range. Refer to the
Understanding NI 9227 Data Rates section for more information.
2 Refer to the Safety Guidelines section for more information about safe operating
voltages.
3 The maximum recommended continuous RMS current value applied simultaneously
on all 4 channels to keep the power dissipation inside the module within safe
operating limits.
4 Overcurrent conditions to keep the module operating within specified limits.
5 The maximum DC current that produces a non-saturated reading.
fM256÷
n
---------------------
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NI 9227 Operating Instructions and Specifications |© National Instruments |19
Input impedance (AI+ to AI-)........... 12 mΩ
Input noise (fs = 50 kS/s)................... 400 μArms
Accuracy at safe operating range of 5 Arms
Accuracy at operating range of 10 Arms
Measurement Conditions
Percent of
Reading
(Gain Error)
Percent of
Range*
(Offset Error)
Calibrated max (-40 to 70 °C) ±0.37% ±0.18%
Calibrated typ (23 °C, ±5 °C) ±0.1% ±0.05%
Uncalibrated max (-40 to 70 °C) ±5.0% ±2.4%
Uncalibrated typ (23 °C, ±5 °C) ±2.5% ±1.0%
*Range equals 7.07 A peak (5 Arms).
Measurement Conditions
Percent of
Reading
(Gain Error)
Percent of
Range*
(Offset Error)
Calibrated max (-40 to 70 °C) ±0.38% ±0.19%
*Range equals 7.07 A peak (5 Arms).
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