HP / Agilent 34401A Digital Multimeter, 6 Digit

The HP/Agilent 34401A is a 6½ digit digital multimeter delivering DC voltage accuracy of 0.0015% (24-hour) and AC voltage accuracy of 0.06% (1-year). Built for both benchtop and automated test environments, it combines precision measurement with high-speed data acquisition—up to 1,000 readings per second directly to GPIB.

## Technical Specifications

**Measurement Functions**
• DC Voltage: 100 mV to 1000 V
• AC Voltage: 100 mV to 750 V True RMS, 3 Hz to 300 kHz bandwidth
• DC Current: 100 µA to 3 A
• AC Current: 100 µA to 3 A True RMS, 3 Hz to 5 kHz bandwidth
• Resistance: 100 Ω to 100 MΩ (2-wire and 4-wire selectable)
• Frequency: 300 Hz to 1 MHz
• Period measurement with AC voltage input ranges
• Continuity testing with audible alarm
• Diode testing to 1.000 V
• dB and dBm measurements

**Accuracy (selected ranges)**
• DC Voltage: 0.0015% of reading + 0.0004% of range (10 V range, 24-hour)
• AC Voltage: 0.06% of reading + 0.03% of range (750 V range, 1-year)
• Resistance (100 Ω range): 0.0030% of reading + 0.0030% of range
• DC Current (1 A range): 0.050% of reading + 0.006% of range
• AC Current (1 A range): 0.10% of reading + 0.04% of range

## Key Features

• Resolution: 6½ digits
• Reading rate: 1,000 readings/second to GPIB
• Internal memory: 512 readings
• Min/Max/Average statistical functions
• Null feature for offset and lead resistance removal
• Reading Hold and Limit Testing with TTL output
• Input Resistance: 10 MΩ standard (high impedance option >10 GΩ on selected ranges)
• Input Bias Current: <30 pA at 25°C
• AC input impedance: 1 MΩ parallel with 100 pF
• Normal Mode Rejection: 60 dB; Common Mode Rejection Ratio: 60 dB

## Measurement Technology

DC voltage uses Continuously Integrating Multi-slope III A-D conversion. AC voltage employs AC-coupled True RMS measurement with up to 400 Vdc bias capability. Resistance employs selectable 4-wire or 2-wire techniques with current source referenced to LO input. Frequency and period employ reciprocal counting.

## Compatibility & Integration

Standard GPIB and RS-232 interfaces enable integration into automated test systems. The instrument supports SCPI, Agilent 3478A, and Fluke 8840A/42A command languages for legacy and modern test software compatibility.