Keysight / Agilent / HP 3478A 5.5 Digit Digital Multimeter

The Keysight/Agilent/HP 3478A is a 5.5-digit digital multimeter engineered for benchtop and automated test system applications. It delivers DC voltage, true RMS AC voltage, 2-wire and 4-wire resistance, DC current, and true RMS AC current measurements with selectable resolution from 3.5 to 5.5 digits. Five autoranging functions streamline measurement setup, while measurement speeds reach 90 readings/second at 3.5-digit resolution and 35 readings/second at 4.5-digit resolution with 130 dB noise rejection. True RMS AC measurements extend to 300 kHz with up to 4:1 crest factor capability. The instrument integrates into automated test systems via HP-IB (IEEE 488) interface with selectable front/rear inputs and external trigger synchronization.

– Technical Specifications

Measurement Functions & Resolution
• DC Voltage: 30 mV to 300 V with 100 nV sensitivity
• True RMS AC Voltage: 300 mV to 300 V, bandwidth to 300 kHz
• DC Current: 300 mA and 3 A ranges
• True RMS AC Current: 300 mA and 3 A ranges
• 2-Wire and 4-Wire Resistance: 30 Ω to 30 MΩ with 100 µΩ sensitivity
• Display Resolution: Selectable 3.5 to 5.5 digits

Performance Specifications
• Measurement Speed: Up to 90 readings/second (3.5 digits); 35 readings/second (4.5 digits)
• DC Voltage Accuracy: ±(0.0034% of reading + 2 counts) at 5.5 digits with auto zero ON
• Input Resistance: 10 GΩ on ranges to 3 V; 10 MΩ ±1% on 30 V and 300 V
• AC Input Impedance: 1 MΩ shunted by <60 pF
• Noise Rejection: 130 dB at 4.5 digits for 50/60 Hz ±0.1%
• Maximum AC Input: 303 V RMS or 450 V peak (Hi to Lo); ±500 V peak (Hi/Lo to Earth Ground)
• DC Current Burden: 0.1 V (300 mA range); 1 V (3 A range)
• Open-Circuit Voltage (Resistance): 6.5 V

Calibration
• Electronic calibration without internal adjustments
• Accuracy specified at 24-hour intervals
• Recommended calibration environment: 20°C to 30°C

– Key Features

• Autoranging across five functions eliminates manual range selection
• True RMS AC measurements to 300 kHz ensure accuracy on nonsinusoidal signals
• Closed-box electronic calibration reduces downtime
• High measurement throughput at 3.5-digit resolution supports rapid data acquisition
• 130 dB line-frequency rejection minimizes noise in industrial environments

– Typical Applications

• Automated test system integration for production and field service
• Component and circuit characterization requiring precision DC and AC measurements
• Low-current and high-resistance measurements in semiconductor and precision electronics
• General-purpose benchtop troubleshooting and verification

– Compatibility & Integration

• HP-IB (IEEE 488) interface for controller communication
• Voltmeter complete output for scanner synchronization
• External trigger input for coordinated multi-instrument measurement sequences
• Front and rear input selection for flexible test configuration