National Instruments NI 9227 User manual

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.
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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.

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.

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

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

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.

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+

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

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