The Keysight L4421A is a 40-channel armature multiplexer for high-density signal routing and switching applications. Built on LXI Class C architecture with native Ethernet connectivity, it delivers remote control and monitoring via an intuitive web interface. The device employs latching relays with break-before-make logic to eliminate signal cross-talk during scans, supports custom switch sequences, and synchronizes measurements via external triggering. Four additional fused inputs enable direct AC and DC current measurement up to 1 A without external shunt resistors. Low thermal offset characteristics and an integrated thermocouple reference junction on the terminal block make the L4421A suitable for precision temperature acquisition when paired with an external DMM. A relay counter monitors contact wear and predicts end-of-life maintenance.
Technical Specifications
• Channels: 40 × 2-wire latching armature relays
• Maximum Signal Voltage: 300 V
• Maximum Switch Current: 1 A
• Carry Current Rating: 2 A
• Scan Rate: Up to 100 channels per second
• Channel Resistance: Typically < 1.5 Ω (may increase to 50 Ω under light-load conditions or after inactivity)
• Current Measurement Inputs: 4 fused inputs (channels 41–44) for AC/DC measurements up to 1 A
• Thermal Offset: Low characteristics for temperature measurement applications
• Thermocouple Reference: On-terminal-block reference junction
• Instrument States: 5 user-labeled states with non-volatile memory
• Power Supply: Universal 100 V to 240 V ±10%, 50 Hz to 60 Hz ±10% (auto-sensed)
• Power Consumption: 15 VA
• Operating Temperature: 0°C to 55°C (full accuracy)
• Storage Temperature: −40°C to 70°C
• Humidity: Up to 80% RH at 40°C
• Dimensions: 40.9 mm H × 212.3 mm W × 379.3 mm D
• Weight: 3.8 kg
– Key Features
• Break-before-make relay switching eliminates simultaneous signal connections
• External trigger inputs for hardware handshake with external DMMs
• Graphical web interface for setup, troubleshooting, and remote monitoring
• Relay counter with end-of-life prediction
• LXI Class C compliant with standard 10BaseT/100BaseTx LAN
• Optional IEEE 488.2 GPIB support
– Typical Applications
• Multi-channel data acquisition and signal routing
• Automated test systems requiring synchronized measurements
• Temperature measurement via thermocouple integration
• AC/DC current monitoring without external scaling resistors
• Laboratory and production test environments
– Compatibility & Integration
Standard Ethernet connectivity supports distributed architectures. Hardware trigger handshake enables tight synchronization with external measurement instruments. Optional GPIB interface accommodates legacy test system integration.
