National Instruments NI 9421 Sinking digital input module

1 image: Click to enlarge

National Instruments · CompactDAQ / CompactRIO

NI 9421

The NI 9421 is an eight-channel C Series digital input module for 24 V industrial signals. It provides sinking inputs and individual channel-state LEDs.

ManufacturerNational Instruments

ModelNI 9421

Part Number783734-01 · 779136-01

Product TypeSinking digital input module

● Available to Order

Condition: confirmed per unit

Request current pricing and lead time for this model. Our team will confirm the exact equipment configuration and condition.

Fast RFQ

Quote: NI 9421

Free Shippingfull policy linked

30-Day Warrantystandard coverage

30-Day Returnspolicy applies

Technical Supportmodel & compatibility help

Inputs8 sinking digital inputs

Logic level24 V

Input delay100 µs maximum

PlatformsCompactDAQ and CompactRIO

SOHO Assistant

Ask about this exact model, a replacement, accessory, driver, rental or repair question.

Ask about specifications, compatibility, availability, rental or repair.

Ask SOHO Assistant

Overview

Product overview

Key product information and technical features.

The NI 9421 connects industrial switches, transducers and other digital devices to modular NI systems. Its channels accept industrial logic signals and provide LED state indication.

The model family includes screw-terminal, spring-terminal and DSUB versions. Connector selection matters because channel-to-earth isolation ratings differ between versions.

Eight dedicated sinking digital input channels.
Individual LEDs indicate channel states.
Isolation between the input channels and earth ground.

Verified specifications

Technical data

Verified product specifications.

Digital input channels	8 channels
Input type	Sinking
Nominal logic level	24 V
Maximum input delay	100 µs
ON-state input voltage	11 to 30 V
OFF-state input voltage	≤5 V
Operating temperature	-40 to 70 °C
Channel-to-channel isolation	None
Continuous channel-to-earth isolation	Screw/spring terminal: 250 Vrms, CAT II; DSUB: 60 VDC, CAT I

Condition & included items

What the actual unit includes

Confirm condition, included accessories and revision before ordering.

Condition

Confirmed per unit.

Included

Device / accessories confirmed in quote.

Revision

Exact revision confirmed when relevant.

Compatibility

Complete the measurement chain

Review system components and compatibility requirements.

National Instruments

Manufacturer

C Series

Module interface and family

NI 9421

Digital input module

System platforms

CompactDAQ and CompactRIO

Confirm the unit's connector and part number before selecting wiring or applying isolation ratings.

Manuals & software

Technical resources

Manuals, software and technical resources for this model.

NI-9421 Product PageProduct Page · ni.com

Open →

NI 9421 DatasheetDatasheet · download.ni.com

Open →

NI-9421 Dimensional DrawingsTechnical resource

Open →

Shipping, warranty & returns

Commercial terms

Review shipping, warranty and return terms before ordering.

Shipping

Free Shipping. Full policy terms apply.

Warranty

30-Day Warranty. Standard coverage applies.

Returns

30-Day Returns. Return policy applies.

Price / Availability

Contact SOHO ProLab for current quote and availability.

Lifecycle services

Source, rent or repair the exact model

Choose pricing, rental or repair for this exact model.

Get Price

Current price, availability and exact unit details.

Rent This Model

Request the exact model or a suitable alternative.

Repair This Model

Send the model and failure symptoms for review.

Explore equipment

CompactDAQ

Shipping, warranty and returns

FAQ

Product-specific questions

Product-specific answers based on available technical information.

Does the NI 9421 provide analog I/O or digital outputs?

No. The NI 9421 is an eight-channel sinking digital input module, not a mixed analog/digital I/O module.

Which connector versions are documented?

NI documents 25-pin DSUB, 10-position screw-terminal and 10-position spring-terminal versions. This catalog record does not identify the specific version.