Agilent/Keysight L4421A

The Agilent/Keysight L4421A is an LXI Class C compliant 40-channel armature multiplexer engineered for signal switching in data acquisition, design verification, and functional test environments. Compact and network-connected via Ethernet, it enables distributed measurement systems with flexible channel configurations - supporting general-purpose scanning or simultaneous multi-channel closure. The module excels in temperature measurement applications through its integrated thermocouple reference junction and low thermal offset characteristics when paired with an external DMM.

Four additional fused inputs route up to 1 A of current to external meters, eliminating the need for external shunt resistors in AC and DC current measurements.

Technical Specifications

• Channel Configuration: 40 switching channels, 2-wire latching armature relays


• Switching Ratings: Signals up to 300 V and 1 A; 2 A carry current


• Scan Rate: Up to 100 channels per second


• Current Inputs: Four fused channels (41–44) rated 1 A maximum for external DMM routing


• Connectors: Standard 50-pin D-sub


• LXI Compliance: Class C


• Interfaces: 10BaseT/100BaseTx Ethernet; optional IEEE 488.2 GPIB


• Web Interface: Java-enabled graphical setup and remote monitoring


• Relay Diagnostics: Counter tracks relay cycle life and predicts end-of-life conditions


• Power Supply: 100 V to 240 V ±10% input; 50 Hz to 60 Hz ±10%; 15 VA consumption


• Operating Temperature: 0°C to 55°C (full accuracy)


• Operating Humidity: Up to 80% RH at 40°C (full accuracy)

Key Features

• Break-before-make relay sequencing prevents signal shorts during multiplexer scans


• Customizable switch sequences for complex measurement routines


• External trigger synchronization for coordinated test events


• Integrated thermocouple reference junction for temperature measurement


• Built-in relay condition monitoring to optimize maintenance scheduling

Typical Applications

• Multi-channel temperature and thermocouple data logging


• AC/DC current measurement without external shunt resistors


• Design verification and functional test signal routing


• Distributed data acquisition over Ethernet networks

Compatibility & Integration Keysight E2094N I/O Libraries Suite included. Supported programming interfaces: IVI-C, IVI-COM, LabVIEW, VEE Pro, TestStand, Measurement Studio, LabWindows/CVI, Switch Executive, Visual Studio .NET, C/C++, and Visual Basic 6.