The HP/Agilent 3581C Selective Level Meter is a portable wave analyzer engineered for precise spectral component measurement across audio and lower radio frequency signals. It separates and quantifies individual frequency components within complex waveforms, delivering both absolute and relative amplitude measurements across an 80 dB dynamic range. The instrument supports multiple input configurations and calibration standards, making it suitable for communications system development, field troubleshooting, and laboratory signal characterization.
Technical Specifications
Frequency Range & Resolution
• Operating range: 15 Hz to 50 kHz
• LED frequency display: 5-digit readout with 1 Hz resolution
• Frequency accuracy: ±3 Hz
• Frequency stability: ±10 Hz/hour typical; ±5 Hz/°C after 1 hour
• Automatic Frequency Control hold-in: ±800 Hz
Input Characteristics
• Selectable input configurations: unbalanced, balanced-bridged, balanced-terminated
• Unbalanced impedance: 1 megohm, 40 pF
• Balanced-bridged impedance: approximately 15 kilohms
• Balanced-terminated impedance: 900 ohms or 600 ohms (front-panel selectable)
• Connector type: Phone-jack input (WECO Type 310 mating plug)
Amplitude Measurement
• Absolute sensitivity: +30 dB/30 V to -70 dB/0.3 mV
• Linear amplitude: 30 V to 100 nV full scale
• Dynamic range (logarithmic): 80 dB
• Calibration modes: dBm/900 ohms, dBm/600 ohms, rms Volts
• Measurement modes: absolute (dBm or dBm/600 ohms), relative (dB or percent of full scale)
• Overload indication: Front-panel LED
Scanning & Signal Processing
• Five selectable bandwidths available
• Scan width: 50 Hz to 50 kHz (adjustable)
• Sweep times: 0.1 S to 2000 S
• Scan modes: single or repetitive
Outputs & Monitoring
• Tracking Oscillator (BFO) output: 600-ohm balanced
• Rear-panel restored output: 600-ohm balanced
• Recorder outputs: X-Y recorder interface for spectral plotting
• Audio monitor: Built-in speaker (3581C)
– Key Features
• Dual power operation: line voltage or battery (Option 001)
• Battery recharge capability via line voltage (Option 901)
• Five independent bandwidth selections for selective measurement
• AFC eliminates manual tuning drift over measurement intervals
– Typical Applications
• Communications system development and validation
• Harmonic and spectral distortion analysis
• Field and laboratory signal characterization
• Frequency response measurement via X-Y recorder output
– Compatibility & Integration
• Phone-jack input accepts WECO Type 310 connectors
• Balanced 600-ohm outputs compatible with standard recorder and audio equipment
• Portable form factor supports laboratory benches and field deployment
