NI-9218 Channel Analog Input Module
“
Specifications
- Product Name: NI-9218
- Connector Types: LEMO and DSUB
- Measurement Types: Built-in support for various types
- Sensor Excitation: Optional 12V excitation
Product Usage Instructions
Connector Types and Pinout
The NI-9218 comes in two connector types: LEMO and DSUB. The
pinout for both types is provided in the user manual.
Signal Descriptions
The product supports various signals for different measurement
types. Refer to the manual for detailed pin descriptions.
Sensor Excitation
To use the optional 12V sensor excitation, connect a 9VDC to
30VDC power supply to Vsup, connect the excitation terminals on
your sensor to EX+/EX-, and enable 12V excitation in your
software.
Loop-Powered Transducer
When connecting a loop-powered 2-wire or 3-wire transducer, add
a 20k resistor between AI- and Ex- to ensure proper
functionality.
Calibration
Utilize remote sensing (RS) and shunt calibration (SC) to
correct errors in excitation leads and resistance within the
bridge.
FAQ
Q: What kind of sensor excitation does the NI-9218
support?
A: The NI-9218 supports optional 12V sensor excitation. Connect
a 9VDC to 30VDC power supply to Vsup, and enable 12V excitation in
your software.
Q: How do I connect a loop-powered transducer to the
NI-9218?
A: When connecting a loop-powered transducer, make sure to add a
20k resistor between AI- and Ex- for proper operation.
Q: What types of connectors does the NI-9218 come with?
A: The NI-9218 comes with two connector types: LEMO and DSUB.
Refer to the manual for more information on the pinouts for each
connector type.
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NI-9218 Getting Started
2025-07-21
NI-9218 Getting Started
Contents
NI-9218 Getting Started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
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NI-9218 Getting Started
NI-9218 Getting Started
Connector Types
The NI-9218 has more than one connector type: NI-9218 with LEMO and NI-9218 with DSUB. Unless the connector type is specified, NI-9218 refers to both connector types.
NI-9218 Pinout
9 8 7 6
5 4 3 2 1
9 8 7 6
5 4 3 2 1
V+ V
4321 10 9
5678
4321 10 9
5678
V+ V+ V- V-
3 © National Instruments
NI-9218 Getting Started
Table 1. Signals by Measurement Type
Mode
Pin 1
2
3
4
±16 V EX+
—
AI-, EX-
—
±65 mV EX+ 2 [2] —
EX- [2]
—
FullBridge
EX+ [2]
—
EX- [2]
RS+
IEPE
—
AI+
AI-
—
TEDS
—
T+ 4
T-
—
5 6 — AI+ — AI+
7 89
—- —
AI- 3 —
—
10 1 — —
RS- AI+ AI- SC SC
—
— — —- —
—
— — —- —
T+ 5
Table 2. Signal Descriptions Signal AI+ AIEX+ EXRS+ RSSC T+ T-
Description Positive analog input signal connection Negative analog input signal connection Positive sensor excitation connection Negative sensor excitation connection Positive remote sensing connection Negative remote sensing connection Shunt calibration connection TEDS data connection TEDS return connection
Measurement Types
The NI-9218 provides built-in support for the following measurement types.
· ±16 V · ±65 mV · Full-Bridge · IEPE
1. NI-9218 with LEMO only. 2. Optional sensor excitation. 3. Tie to pin 3. 4. TEDS Class 1 data connection. 5. TEDS Class 2 data connection.
4 ni.com
NI-9218 Getting Started
Tip NI-recommends using the NI-9982 screw-terminal adapter when using
built-in measurement types on the NI-9218.
The NI-9218 provides additional support for the following measurement types when using a measurement-specific adapter.
· ±20 mA, requires the NI-9983 · ±60 V, requires the NI-9987 · Half-Bridge, requires the NI-9986 · Quarter-Bridge, requires the NI-9984 (120 ) or NI-9985 (350 )
±16 V Connections
+ –
VEX+ VEX-
AI+ AI- /EX –
VSUP+
EX+
VSUP-
NI-9218
The NI-9218 provides optional 12 V sensor excitation. To use the 12 V excitation, connect a 9 VDC to 30 VDC power supply to Vsup, connect the excitation terminals on your sensor to EX+/EX-, and enable 12 V excitation in your software.
Related reference:
· NI-9982 ±16 V Connection Pinout
±65 mV Connections
5 © National Instruments
NI-9218 Getting Started
+ –
VEX+ VEX-
AI+
VSUP+
VSUP-
AI –
EX+
EXNI-9218
· You must connect AI- to EX- on the NI-9218. · The NI-9218 provides optional 12 V sensor excitation. To use the 12 V excitation,
connect a 9 VDC to 30 VDC power supply to Vsup, connect the excitation terminals on your sensor to EX+/EX-, and enable 12 V excitation in your software.
Related reference:
· NI-9982 ±65 mV Connection Pinout
Full-Bridge Connections
RS+ EX+ AI+ AI
EX RS SC SC
NI-9218
· The NI-9218 provides 2 V excitation to loads 120 or 3.3 V excitation to loads 350 .
· The NI-9218 provides optional connections for remote sensing (RS) and shunt calibration (SC). Remote sensing corrects for errors in excitation leads and shunt calibration corrects for errors caused by resistance within one leg of the bridge.
6 ni.com
Related reference: · NI-9982 Full-Bridge Connection Pinout
IEPE Connections
NI-9218 Getting Started
AI+ + –
AINI-9218
· The NI-9218 provides an excitation current for each channel that powers IEPE sensors.
· AI+ provides DC excitation and AI- provides the excitation return path.
Related reference:
· NI-9982 IEPE Connection Pinout
±20 mA Connections
VEX+ VEX-
AI+ AIEX+ EX-
NI-9983
DSUB/LEMO
VSUP+
VSUP-
NI-9218
· Connecting ±20 mA signals requires the NI-9983. · The NI-9218 provides optional 12 V sensor excitation. To use the 12 V excitation,
connect a 9 VDC to 30 VDC power supply to Vsup, connect the excitation terminals on your sensor to EX+/EX-, and enable 12 V excitation in your software.
7 © National Instruments
NI-9218 Getting Started
Connecting a loop-powered 2-wire or 3-wire transducer requires adding a 20 k resistor between AI- and Ex-.
Loop-Powered Transducer
AI+
AI-
EX+ 20 k EX-
NI-9983
Related reference: · NI-9983 Pinout
±60 V Connections
DSUB/LEMO
VSUP+
VSUP-
NI-9218
DSUB/LEMO
AI+ +
–
AI-
NI-9987
NI-9218
Connecting ±60 V signals requires the NI-9987. Related reference:
· NI-9987 Pinout
Half-Bridge Connections
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RS+ EX+
AI+
EXRSSC SC
NI-9986
DSUB/LEMO
NI-9218
NI-9218 Getting Started
· Connecting half bridges requires the NI-9986. · The NI-9218 provides 2 V excitation to half bridges of 240 total or 3.3 V
excitation to half bridges of 700 total. · The NI-9218 provides optional connections for remote sensing (RS) and shunt
calibration (SC). Remote sensing corrects for errors in excitation leads and shunt calibration corrects for errors caused by resistance within one leg of the bridge.
Related reference:
· NI-9986 Pinout
Quarter-Bridge Connections
EXC
DSUB/LEMO
AI
RC NI-9984/9985
NI-9218
· Connecting 120 quarter bridges requires the NI-9984. · Connecting 350 quarter bridges requires the NI-9985.
9 © National Instruments
NI-9218 Getting Started
Tip NI-recommends 2 V excitation when using a NI-9984 with 120 quarter
bridges and 3.3 V excitation when using the NI-9985 with 350 quarter bridges. Related reference: · NI-9984/9985 Pinout
TEDS Connections
Data
TEDS
COM
Enabled Sensor
T+
TNI-9218
For more information about TEDS, visit ni.com/info and enter the Info Code rdteds.
TEDS Support
TEDS Class 1 sensors provide an interface for transferring information from sensors. The NI-9218 with LEMO, NI-9218 with DSUB, NI-9982L, NI-9982D, NI-9982F support TEDS Class 1 sensors.
TEDS Class 2 sensors provide an interface for transferring information from TEDS enabled sensors. The NI-9218 with LEMO, NI-9982L, NI-9983L, NI-9984L, NI-9985L, and NI-9986L support TEDS Class 2 sensors.
Vsup Daisy Chain Topology
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Vsup+ Vsup- Vsup+ Vsup- Vsup+ Vsup- Vsup+ Vsup- Vsup+ Vsup- Vsup+ Vsup-
NI-9218 Getting Started
NI-9218 with LEMO
NI-9218 with LEMO
NI-9218 with LEMO
The NI-9218 with LEMO provides four pins on the Vsup connector for daisy chaining.
NI-9218 Connection Guidelines
Make sure that devices you connect to the NI-9218 are compatible with the module specifications.
Custom Cabling Guidelines
Observe the following guidelines when using the NI-9988 solder cup connector adapter or the LEMO crimp connector (784162-01) to create custom cables.
· Use a shielded cable for all signals. · Connect the cable shield to earth ground. · Use twisted-pair wiring for the AI+/AI- and RS+/RS- signals to achieve specified EMC
performance.
AI+ AIRS+ RS-
Additional Signals
Shield
AI+ AIRS+ RS-
Additional Signals
DSUB/LEMO
Sensor
NI-9988
NI-9218
11 © National Instruments
NI-9218 Getting Started
NI-9218 Block Diagram
Input Connector
CH0 CH1 Vsup
Power Connector
Input Connector
Measurement Type Signal Conditioning
Isolation
ADC
Isolator
12 V Excitation
Measurement Type Signal Conditioning
Isolation
ADC
Isolator
12 V Excitation
External Power Supply
NI-9218
Legend
Hardware Components Software-Selectable Externally Supplied Voltage Data
· Two 24-bit analog-to-digital converters (ADCs) simultaneously sample both AI channels.
· The NI-9218 provides channel-to-channel isolation. · The NI-9218 reconfigures the signal conditioning for each measurement type. · The NI-9218 provides excitation for IEPE and bridge completion measurement
types. · The NI-9218 can provide optional 12 V sensor excitation for ±16 V, ±65 mV, and ±20
mA measurement types.
±16 V and ±65 mV Signal Conditioning
AI+
Overvoltage
AI-
Protection
Amplifier Prefilter
ADC NI-9218
Input signals on each channel are buffered, conditioned, and then sampled by an ADC.
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Full-Bridge Signal Conditioning
NI-9218 Getting Started
RS+
EX+
+
AI+
AI
EX
RS
SC
SC
Reference Input
ADC
NI-9218
· The analog input connections sense then amplify the incoming analog signal. · The excitation connections provide differential bridge-excitation voltage. · Remote sensing continuously and automatically corrects for lead-wire induced
excitation voltage loss when using the RS connections. · Shunt calibration can be used to correct for lead-wire induced desensitization of
the bridge.
IEPE Signal Conditioning
2 mA IEPE
AC Coupling
AI+ +
ADC
AI-
Amplifier and
Prefilter
NI-9218
· The incoming analog signal is referenced to an isolated ground.
13 © National Instruments
NI-9218 Getting Started
· Each channel is configured for AC coupling with an IEPE current. · Each channel provides a TEDS Class 1 interface.
±20 mA Signal Conditioning
DSUB/LEMO
AI+
Current
AI-
Shunt
Overvoltage Protection
Amplifier Prefilter
ADC NI-9218
The NI-9983 provides a current shunt for the incoming analog signal.
±60 V Signal Conditioning
DSUB/LEMO
AI+
Overvoltage
AI-
Protection
ADC
Amplifier Prefilter
NI-9218
The NI-9987 provides an attenuator for the incoming analog signal.
Half-Bridge Signal Conditioning
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NI-9218 Getting Started
RS+ Reference
EX+
+
AI+
Input ADC
DSUB/LEMO
EX RS SC SC
NI-9218
· The NI-9886 provides half bridge completion resistors for the incoming analog signal.
· You must connect AI+, EX+, and EX-. · RS+ and RS- connections are optional. · You do not need to connect the AI- signal because it is connected internally.
Quarter-Bridge Mode Conditioning
EXC
Reference
+ AI+
Input ADC
RC
DSUB/LEMO
NI-9984/9985
NI-9218
The NI-9984 and NI-9985 provide a quarter-bridge completion resistor and half-bridge
15 © National Instruments
NI-9218 Getting Started
completion resistors.
Filtering
The NI-9218 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-9218 represents signals within the passband, as quantified primarily by passband ripple 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-9218 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.
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-9218 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.
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Opening a Measurement Adapter
What to Do
NI-9218 Getting Started
1
2
1. Unlock the measurement adapter housing/cover. 2. Slide the measurement adapter housing/cover to access the screw terminals.
Mounting the NI-998xD/998xL
What to Use
· NI-998xD or NI-998xL Measurement Adapter · M4 or Number 8 Screw · Screwdriver
What to Do
Mount the measurement adapter to a flat surface using the mounting hole on the 17 © National Instruments
NI-9218 Getting Started
measurement adapter and the screw.
Measurement Adapter Grounding
The ground terminals on a measurement adapter are connected to chassis ground when the measurement adapter is connected to the NI-9218 and the NI-9218 is installed in a chassis.
Measurement Adapter Pinouts
The following sections include pinouts for the NI-9218 measurement adapters.
NI-9982 ±16 V Connection Pinout
—
5
—
4
AI-,
3b
EX-
3a
—
2
EX+
1
6
AI+
7
—
8
—
9
—
10
—
4– 5–
1 EX+ 6 AI+ 2 — 7–
3a AI-, 8 — 3b EX- 9 —
NI-9982F
NI-9982D/9982L
Pins 3a and 3b are tied together on the NI-9982. Related reference:
· ±16 V Connections
NI-9982 ±65 mV Connection Pinout
18 ni.com
—
5
—
4
EX-
3b 3a
—
2
EX+
1
6
AI+
7
AI-
8
—
9
—
10
—
4 — 1 EX+ 6 AI+
5 — 2 — 7 AI-
3a 3b
EX-
8 9
— —
NI-9982F
NI-v9982D/9982L
Pins 3a and 3b are tied together on the NI-9982. Related reference:
· ±65 mV Connections
NI-9982 Full-Bridge Connection Pinout
RS-
5
RS+
4
EX-
3b 3a
—
2
EX+
1
6
AI+
7
AI-
8
SC
9
SC
10
—
4 RS+ 1 EX+ 6 AI+
5 RS- 2 — 7 AI-
3a 3b
EX-
8 SC 9 SC
NI-9982F
NI-9982D/9982L
Pins 3a and 3b are tied together on the NI-9982. Related reference:
· Full-Bridge Connections
NI-9982 IEPE Connection Pinout
NI-9218 Getting Started
19 © National Instruments
—
5
—
4
AI-
3b 3a
AI+
2
—
1
6
—
7
—
8
—
9
—
10
—
4– 5–
1 — 6–
2 AI+ 7 —
3a 3b
AI-
8– 9–
NI-9982F
NI-9982D/9982L
Pins 3a and 3b are tied together on the NI-9982. Related reference:
· IEPE Connections
NI-9983 Pinout
—
5
—
4
EX-
3b 3a
—
2
EX+
1
6
AI+
7
AI-
8
—
9
—
10
—
4 — 1 EX+ 6 AI+
5 — 2 — 7 AI-
3a EX- 8 —
3b
9–
NI-9983F
NI-9983D/9983L
Pins 3a and 3b are tied together on the NI-9983. Related reference:
· ±20 mA Connections
NI-9984/9985 Pinout
20 ni.com
NI-9218 Getting Started
—
5
—
4
—
3b
RC
3a
—
2
EXC
1
6
AI
7
—
8
—
9
—
10
—
4 — 1 EXC 6 AI 5– 2– 7–
3a RC 8 — 3b — 9 —
NI-9984F/9985F
NI-9984D/9984L/9985D/9985L
Related reference: · Quarter-Bridge Connections
NI-9986 Pinout
RS-
5
RS+
4
EX-
3b 3a
—
2
EX+
1
6
AI
7
—
8
SC
9
SC
10
—
4 RS+ 1 EX+ 6 AI
5 RS- 2 — 7 —
3a 3b
EX-
8 SC 9 SC
NI-9986F
NI-9986D/9986L
Pins 3a and 3b are tied together on the NI-9986. Related reference:
· Half-Bridge Connections
NI-9987 Pinout
NI-9218 Getting Started
21 © National Instruments
—
5
—
4
AI-
3b 3a
—
2
—
1
6
AI+
7
—
8
—
9
—
10
—
4 — 1 — 6 AI+
5 — 2 — 7–
3a 3b
AI-
8– 9–
NI-9987F
NI-9987D/9987L
Pins 3a and 3b are tied together on the NI-9987. Related reference:
· ±60 V Connections
NI-9218 Getting Started
22 ni.com
© 2025 National Instruments Corporation.
Documents / Resources
 |
National Instruments NI-9218 Channel Analog Input Module [pdf] Instruction Manual NI-9218 with LEMO, NI-9218 with DSUB, NI-9218 Channel Analog Input Module, NI-9218, Channel Analog Input Module, Analog Input Module, Input Module |