National Instruments NI 9227E User manual

OPERATING INSTRUCTIONS AND SPECIFICATIONS
NI 9227E
4-Channel, 5 Arms, 24-Bit, Simultaneous,
Channel-to-Channel Isolated Analog Input Module

NI 9227E Operating Instructions and Specifications 2 ni.com
This document describes how to use the National Instruments 9227E
and includes dimensions, terminal assignments, and specifications for
the NI 9227E. Visit ni.com/info and enter rdsoftwareversion
to determine which software you need for the modules you are 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.
Caution National Instruments makes no electromagnetic
compatibility (EMC) or CE marking compliance claims
for the NI 9227E. The end-product supplier is responsible
for conformity to any and all compliance requirements.
Caution The NI 9227E must be installed inside a suitable
enclosure prior to use. Hazardous voltages may be present.

© National Instruments Corp. 3 NI 9227E Operating Instructions and Specifications
NI 9227E Dimensions
The following figure shows the dimensions of the NI 9227E.
Figure 1. NI 9227E Dimensions in Millimeters (Inches)
0.0 (0.00)
26.7 (1.05) 58.4 (2.30) 66.0 (2.60)
73.4 (2.89)
0.0 (0.00)

NI 9227E Operating Instructions and Specifications 4 ni.com
Connecting the NI 9227E
The NI 9227E has four 2-terminal detachable screw-terminal
connectors that provide connections for four simultaneously
sampled, isolated analog input channels.
Figure 2. NI 9227E Terminal Assignments
AI0+
AI0–
AI1+
AI1–
AI2+
AI2–
AI3+
AI3–
0
1
0
1
0
1
0
1

© National Instruments Corp. 5 NI 9227E Operating Instructions and Specifications
You can connect ground-referenced or floating current sources to
the NI 9227E. 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 9227E, 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 9227E.
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 9227E.
Refer to Figures 3 and 4 for illustrations of how to connect
grounded and floating current sources to the NI 9227E.

NI 9227E Operating Instructions and Specifications 6 ni.com
Figure 3. Connecting a Grounded Current Source to the NI 9227E
Figure 4. Connecting a Floating Current Source to the NI 9227E
NI 9227E
Current
Source
AI–
AI+
NI 9227E
Current
Source
AI–
AI+

© National Instruments Corp. 7 NI 9227E Operating Instructions and Specifications
The NI 9227E 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 9227E.
Figure 5. Input Circuitry for One Channel of the NI 9227E
NI 9227E
AI+
AI–
ADC
Amplifier
Shunt
Resistor
Prefilter

NI 9227E Operating Instructions and Specifications 8 ni.com
Understanding NI 9227E Filtering
The NI 9227E 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 9227E 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 9227E 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 6 shows typical
passband flatness for the NI 9227E.

© National Instruments Corp. 9 NI 9227E Operating Instructions and Specifications
Figure 6. Typical Passband Flatness for the NI 9227E
Frequency/Data Rate (Hz)
0.50.4
0.025
0.000
–0.025
–0.050
0.30.20.10
Gain (dB)

NI 9227E Operating Instructions and Specifications 10 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 9227E 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 9227E Data Rates
The frequency of a master timebase ( fM) controls the data rate ( fs)
of the NI 9227E. The NI 9227E 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 9227E with other
modules that use master timebases to control sampling, all of the