Agilent/Keysight 34420A

The Keysight 34420A is a 7½ digit nanovolt/micro-ohm meter engineered for precision low-level measurements across voltage, resistance, and temperature applications. It delivers 100 pV sensitivity on DC voltage and 100 nΩ sensitivity on resistance, with exceptional 1.3 nVrms noise performance. The instrument combines a continuously integrating multi-slope III A-D converter with selectable analog and digital filtering to extract signals buried in noise-prone environments.

– Technical Specifications

DC Voltage Measurement:
• Ranges: 1 mV to 100 V
• Basic accuracy: 0.003% over 1 year; 2 ppm over 24 hours
• Input resistance: >10 GΩ (1 mV–10 V ranges); 10 MΩ ±1% (100 V range, Channel 1)
• Input bias current: <50 pA at 25 °C

Resistance Measurement:
• Ranges: 1 Ω to 1 MΩ
• 4-wire and 2-wire selectable configurations
• Low Power Resistance and Voltage-Limited modes available
• Open circuit voltage: <14 V with selectable 20 mV, 100 mV, or 500 mV clamps

Temperature Measurement:
• SPRT (ITS-90): −190 °C to +660 °C
• RTD (Type α = 0.00385/0.00392): R₀ from 4.9 Ω to 2.1 kΩ with IEC-751 conversion
• Thermocouple types B, E, J, K, N, R, S, T with ITS-90 conversion
• Accuracy: 0.003 °C

Noise & Filtering:
• 1.3 nVrms; 8 nVpp performance
• Analog filter: 13 Hz low-pass, 2-pole (1 mV, 10 mV, 100 mV ranges)
• Digital filter: 10, 50, or 100 reading moving average

– Key Features

• Built-in 2-channel low-noise scanner
• Ratio and difference measurement functions
• 1024-reading memory with statistics (Min, Max, Average, Peak-Peak, Standard Deviation)
• GPIB (IEEE-488) and RS-232 interfaces
• SCPI and Keithley 181 command compatibility
• Offset compensation for thermal EMF rejection

– Physical & Electrical

• Dimensions: 104 mm H × 254 mm W × 374 mm D
• Weight: 7 lb
• Supply: 100 V/120 V/220 V/230 V/240 V ±10%; 45–66 Hz and 360–440 Hz auto-sensed
• Front panel: Shielded, low-thermal 99% copper contacts

– Typical Applications

Precision research metrology, device characterization, low-noise bridge balancing, thermal measurements in cryogenic systems, and calibration verification in standards laboratories.