Comprehensive Product Summary: ADLINK PXI-7921 Relay Multiplexer Module

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### 1. Product Overview

Product Name: PXI-7921
Model Number: PXI-7921
Series: PXI / CompactPCI 3U Switch Module Series
Article Number: PXI-7921
Manufacturer: ADLINK Technology Inc.
Product Type: PXI cPCI 3U 24-Channel 2 Form C 2A Relay Card (24-CH 2-Wire Multiplexer Module)
Form Factor: 3U Eurocard, CompactPCI (PICMG 2.0 R3.0)
Manufacturer Website: [www.adlinktech.com](http://www.adlinktech.com)
Part Number: 50-17011-100
Manual Revision: 1.00 (July 9, 2004)

The ADLINK PXI-7921 is a high-performance PXI relay multiplexer module designed for automated test, measurement, and control systems. It integrates 24 independent 2-wire relays (DPDT, 2 Form C) and supports multiple multiplexer configurations through software control. The module is fully compliant with PXI and CompactPCI standards, offering hot-swap capability, deterministic scanning, and synchronization features for complex test environments.

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### 2. Key Features

- PXI and CompactPCI Compliance:
- PXI Specification Rev. 2.2 compliant
- CompactPCI (PICMG 2.0 R3.0) and Hot Swap (PICMG 2.1 R2.0) compliant

- Relay Configuration:
- 24-channel DPDT (2 Form C) non-latching relays
- Configurable as 48×1 (1-wire), 24×1 (2-wire), or 12×1 (4-wire) multiplexer
- Software-selectable configuration without hardware jumpers

- Switching Performance:
- 2 A switching and carrying current
- 220 V DC / 125 V AC maximum switching voltage
- 60 W maximum switching power

- Deterministic Scanning:
- Onboard 1 k-sample scan list memory for auto-scan operation
- Supports direct-update and auto-scan modes
- Programmable scan delay and trigger synchronization

- Synchronization and Triggering:
- PXI trigger bus and star trigger support
- Programmable handshaking signals (TRG_IN, S_ADV)
- Multiple module synchronization without external wiring

- Safety and Reliability:
- Programmable emergency shutdown function
- 32-bit watchdog timer (1 ms to 420 s)
- Relay safety status programmable via software

- Software and OS Support:
- Supported OS: Windows 2000, XP, Vista, 2003
- Driver: ADL-SWITCH for Windows
- Recommended software: VB, VC++, BCB, Delphi, DAQBench

- Hot-Swap Capability:
- Fully compliant with CompactPCI Hot Swap specifications
- Supports Microsoft Embedded XP native hot-swap

- Auxiliary Digital I/O:
- Three 3.3 V/TTL (5 V tolerant) digital I/O lines
- Programmable as input/output/tri-state

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### 3. Technical Specifications

Physical Dimensions:
- 160 mm (L) × 100 mm (H) (excluding connectors)
- Form Factor: PXI 3U Eurocard

Weight:
- Approx. 0.5 kg (typical for PXI 3U modules)

Relay Characteristics:
- Type: DPDT (2 Form C), non-latching
- Channels: 24 (2-wire)
- Max. Switching Current: 2 A
- Max. Carrying Current: 2 A
- Max. Switching Voltage: 220 V DC / 125 V AC
- Max. Switching Power: 60 W (50 VA)
- Contact Resistance: ≤100 mΩ
- Operate Time: ≤4 ms
- Release Time: ≤4 ms
- Bounce Time: ≤1 ms
- Mechanical Life: ≥10⁸ operations
- Electrical Life: ≥5×10⁵ operations (1 A @ 30 V DC resistive load)

Power Requirements:
- +5 V @ 1 A
- +3.3 V @ 400 mA

Environmental Conditions:
- Operating Temperature: 0°C to 55°C
- Storage Temperature: -20°C to 70°C
- Relative Humidity: 5% to 85% (non-condensing)

Connector:
- 62-pin D-sub male (front panel I/O)

EMC/EMI Compliance:
- CE, FCC Class A

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### 4. Functionality

The PXI-7921 functions as a flexible relay-based multiplexer for routing analog or digital signals between instruments and multiple test points. It can operate in several configurations:

- 1-Wire Mode: 48×1 multiplexer
- 2-Wire Mode: 24×1 multiplexer
- 4-Wire Mode: 12×1 multiplexer
- Grouped Configurations: Two 12×1 or four 6×1 multiplexers

Operation Modes:
- Direct-Update Mode: Immediate relay switching upon software command.
- Auto-Scan Mode: Sequential relay switching based on a preloaded scan list (up to 1024 entries).

Use Cases:
- Automated test equipment (ATE)
- Industrial and laboratory automation
- Signal routing for DMMs, digitizers, or signal sources
- ON/OFF control and high-power relay driving
- Limit switch monitoring and contact sensing

Compatibility:
- PXI chassis and controllers
- Compatible with ADLINK terminal boards (TB-6221-01) and cables (ACL-10262)
- Integrates with other PXI modules for synchronized data acquisition and control

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### 5. Components & Accessories

Included Items:
- PXI-7921 module
- User’s Manual
- ADLINK Software CD (includes ADL-SWITCH drivers and utilities)
- ADL-SWITCH User’s Guide

Optional Accessories:
- TB-6221-01: Multiplexer Switch Terminal Board with 62-pin D-sub female connector
- ACL-10262: 62-pin D-sub male/female cable, 1 meter length

Connectors:
- Front Panel: 62-pin D-sub male
- Rear: PXI J1/J2 connectors for backplane interface

Pin Assignments (CN1):
- Channels: CH0± to CH23±
- Commons: COM0± to COM3±
- Trigger and Control: TRG_IN, S_ADV, SHDNn
- Power: +5Vout, GND
- Reference: 1WireLoRef

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### 6. Installation & Setup

Requirements:
- PXI or CompactPCI chassis with available 3U slot
- Compatible PXI controller or embedded PC
- Windows OS with ADL-SWITCH driver installed

Installation Steps:
1. Power off the PXI chassis before inserting the module (unless hot-swap supported).
2. Align the PXI-7921 with the chassis card guide and slide it into the slot.
3. Push the ejector handle upward until the module clicks into place.
4. Secure the front panel screws.
5. Connect the terminal board or cable to the front I/O connector.
6. Power on the chassis and verify module recognition via software.

Hot-Swap Procedure:
- Supported under Microsoft Embedded XP.
- For Windows 2000, manual hot-swap driver required.

Configuration:
- Software-based configuration via ADL-SWITCH API.
- No hardware jumpers required for mode selection.

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### 7. Performance & Capabilities

Switching Speed:
- Operate/Release Time: ≤4 ms
- Maximum Switching Rate: 125 operations per second

Capacity:
- 24 independent channels (2-wire)
- Configurable multiplexing up to 48×1 (1-wire)

Efficiency:
- Low contact resistance ensures minimal signal loss.
- Deterministic scanning with 1k-entry onboard memory.

Synchronization:
- PXI trigger bus and star trigger enable multi-module coordination.
- Handshaking signals (TRG_IN, S_ADV) synchronize with external instruments.

Limitations:
- Non-latching relays (requires continuous power for state retention).
- Maximum switching power limited to 60 W.
- Operating temperature limited to 55°C.

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### 8. Standards & Compliance

PXI and CompactPCI Standards:
- PXI Specification Rev. 2.2
- CompactPCI PICMG 2.0 R3.0
- CompactPCI Hot Swap PICMG 2.1 R2.0

Electrical and Safety Standards:
- Logic Level Compatibility: 3.3 V/TTL (5 V tolerant)
- Reverse Input Voltage Protection: -0.5 V to +5.5 V

EMC/EMI Compliance:
- CE Certified
- FCC Class A

Environmental Compliance:
- Designed for industrial environments (0°C–55°C operation)
- Humidity tolerance up to 85% non-condensing

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### 9. Additional Information

Warranty:
- Standard 2-year manufacturer warranty from shipment date.
- Covers defects in materials and workmanship.
- Excludes damage from misuse, improper storage, or unauthorized repair.

Support & Service:
- Technical Support: service@adlinktech.com
- Telephone: +886-2-82265877
- Fax: +886-2-82265717
- Address: 9F, No. 166, Jian Yi Road, Chungho City, Taipei 235, Taiwan

Maintenance:
- Periodic inspection of relay contacts recommended for high-cycle applications.
- Use anti-static precautions during handling.
- Store in dry, temperature-controlled environment.

Software Updates:
- ADL-SWITCH driver updates available via ADLINK website.
- Includes sample code and utilities for Visual Basic, C/C++, Delphi, and DAQBench.

Documentation:
- User’s Manual (Rev. 1.00)
- ADL-SWITCH Software User’s Guide
- Terminal Board (TB-6221) Reference

Regulatory Notes:
- All specifications subject to change without notice.
- Product designed and manufactured in compliance with international PXI standards.

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### Summary

The ADLINK PXI-7921 is a robust, software-programmable 24-channel DPDT relay multiplexer module optimized for PXI-based automated test and measurement systems. It provides flexible signal routing, deterministic scanning, and synchronization capabilities across multiple instruments. With its 2 A switching capacity, multi-mode configuration, and PXI trigger integration, the PXI-7921 is ideal for industrial automation, laboratory testing, and safety-critical applications requiring reliable, high-speed signal switching.

Its hot-swap support, watchdog timer, and emergency shutdown functions enhance operational safety and uptime, while ADLINK’s ADL-SWITCH driver suite ensures seamless integration with Windows-based test software environments.

The PXI-7921 exemplifies ADLINK’s commitment to modular, high-performance PXI instrumentation, offering precision, flexibility, and reliability for demanding test and control applications.