The Keysight (Agilent) 400FL AC Voltmeter is a precision instrument for accurate AC voltage and decibel measurements across a broad frequency spectrum from 20 Hz to 4 MHz. This analog meter delivers high input impedance and reliable performance in laboratory and field environments, with the unique ability to function as a wideband amplifier.
Technical Specifications
Measurement Ranges & Accuracy
• Voltage measurement: 100 µV to 300 V full scale across 14 ranges (1, 3, 10 sequence)
• Responds to absolute average value, calibrated in RMS Volts
• Decibel measurement with linear dB scale and logarithmic AC scale
• Accuracy: ±4% (20–40 Hz), ±2% (40–100 Hz), ±1% (100 Hz–1 MHz), ±2% (1–2 MHz), ±4% (2–4 MHz)
Frequency & Input Characteristics
• Frequency response: 20 Hz to 4 MHz (1 mV to 300 V ranges); 30 Hz to 100 kHz (100 µV and 300 µV ranges)
• Selectable 100 kHz filter available on lowest ranges
• Input impedance: 10 MΩ shunted by 25 pF (100 µV–300 mV ranges) or 10 pF (1 V–300 V ranges)
Amplifier & Output
• AC amplifier output: 1 V RMS open circuit at full-scale meter indication
• Output impedance: 600 Ω
• Meter response: Approximately 0.7 seconds; recovery from 80 dB overload in less than 2 seconds
Power & Physical
• AC supply: 115 or 230 VAC ±10%, 50–1000 Hz, ~5 watts
• External battery operation: ±35 V to ±55 V, ~45 mA per supply
• Dimensions: 6.5″ H × 5.125″ W × 11″ D (165.1 × 130.2 × 279.4 mm)
• Weight: 6 lbs net (2.7 kg); 9 lbs shipping (4 kg)
• Operating temperature: 0 to +55°C
• Display: Analog meter with mirror-backed taut-band galvanometer
– Key Features
• Dual-scale display: linear dB with logarithmic AC scale
• High input impedance minimizes loading effects
• Wideband amplifier functionality for signal analysis
• Fast meter response and rapid overload recovery
• Flexible power options for portable and bench-top use
– Typical Applications
• AC voltage measurements in audio and RF circuits
• Decibel measurements across telecommunications frequencies
• Amplified signal measurement and analysis
• Field service and laboratory testing to 4 MHz
– Compatibility & Integration
The 400FL accepts standard AC signals and integrates with external amplification or measurement systems via its 600 Ω output impedance.
