The HP/Agilent 3478A is a 5.5-digit digital multimeter engineered for benchtop and automated test environments. It delivers DC voltage, true RMS AC voltage and current, and 2- and 4-wire resistance measurements through an HP-IB interface. Selectable resolution modes—3.5, 4.5, and 5.5 digits—allow users to trade measurement speed for noise rejection and precision. The 4.5-digit mode achieves 130 dB noise rejection with 35 readings/second; the 5.5-digit mode delivers 100 nV resolution. Closed-box electronic calibration eliminates mechanical adjustments and supports both manual front-panel and automated HP-IB control.
## Technical Specifications
**Measurement Functions:**
• DC Voltage: 30 mV to 300 V (100 nV sensitivity)
• AC Voltage (true RMS): 300 mV to 300 V, up to 300 kHz bandwidth, 4:1 crest factor
• DC Current: 300 mA, 3 A ranges
• AC Current (true RMS): 300 mA, 3 A ranges, up to 20 kHz bandwidth
• Resistance (2- and 4-wire): 30 Ω to 30 MΩ (100 µΩ sensitivity)
**Performance:**
• Basic DC voltage accuracy: ±(0.0034% of reading + 2 counts)
• Measurement rates: up to 90 readings/second (3.5-digit), 35 readings/second (4.5-digit with 130 dB noise rejection)
• AC line rejection: 50, 60 Hz ± 0.1%
• Display: 5.5-digit LED
**Input Specifications:**
• DCV input impedance: 10 GΩ (≤3 V); 10 MΩ ± 1% (30 V, 300 V)
• ACV input impedance: 1 MΩ shunted by < 60 pF
• Overvoltage protection: ±350 V peak (Hi to Lo), ±500 V peak (Hi or Lo to Earth Ground)
• Resistance open-circuit voltage: 6.5 V
• Current burden: 0.1 V (300 mA), 1 V (3 A)
## Key Features
• Closed-box electronic calibration—no internal adjustments required
• Built-in self-test capabilities
• HP-IB programmable interface for system integration
• Voltmeter Complete output for scanner synchronization
• Low cost of ownership through automated calibration
## Typical Applications
• Automated test environments and data acquisition systems
• Precision DC and AC measurements in production test
• High-resolution resistance and current characterization
• Systems requiring noise-rejection and fast measurement cycling
## Compatibility & Integration
HP-IB (IEEE-488) interface enables remote programming and automated measurement sequencing. Voltmeter Complete output synchronizes with multiplexer systems for rapid multi-channel testing.
