HP / Agilent 53181A RF Frequency Counter, 10 digits/s

The HP/Agilent 53181A is a RF frequency counter delivering 10-digit resolution at measurement speeds up to 200 measurements per second. Built for precision RF testing, it measures frequency from DC to 225 MHz on the primary channel, with optional second-channel capability extending to 1.5 GHz, 3 GHz, 5 GHz, or 12.4 GHz. The instrument combines fast acquisition with low sensitivity - 20 mVrms from DC to 100 MHz, scaling to 40 mVrms at 200–225 MHz - making it ideal for weak-signal detection in demanding RF environments.

Technical Specifications Measurement Capabilities

Frequency and period with 10 digits per second resolution

Time interval measurement with 500 ps resolution

Pulse width, rise/fall time, duty cycle, and totalize functions

Phase angle and peak voltage measurements

Ratio measurement when second channel is installed Primary Channel (Channel 1)

Frequency range: DC to 225 MHz

Sensitivity: 20 mVrms (DC to 100 MHz); 30 mVrms (100–200 MHz); 40 mVrms (200–225 MHz)

Input impedance: 50 Ω or 1 MΩ, AC or DC coupled

Peak input voltage: ±5 Vac + dc (DC to 100 MHz) Optional Second Channel (Channel 2)

Selectable bandwidth: 1.5 GHz, 3 GHz, 5 GHz, or 12.4 GHz

Sensitivity: 30 mVrms across rated frequency range Time Base Stability

Standard: <3 × 10⁻⁷/month (10 MHz)

Option 010 (High-stability): <1.55 × 10⁻⁸/month

Option 012 (Ultra-high stability oven): <3 × 10⁻⁹/month; <2 × 10⁻⁹/year Performance & Automation

Built-in statistics: average, min/max, standard deviation

Automated limit testing with pass/fail indication

Digit blanking for streamlined readout

Operating temperature: 0°C to 55°C

Measurement altitude: up to 3000 m

Key Features

Dual-channel configuration with independent frequency ranges

GPIB (IEEE-488) and RS-232 standard interfaces; USB optional

Compact form factor: 89 mm H × 213 mm W × 348 mm D; 7 lb

Multiple input options including rear connectors for instrumentation racks

Typical Applications RF signal characterization, frequency stability monitoring, phase measurement, pulse analysis, and production test automation in RF design and manufacturing environments.

Compatibility & Integration Standard GPIB control supports integration into automated test systems. RS-232 talk-only mode provides legacy instrument communication. Optional USB interface enables modern data acquisition workflows. Configurable input coupling and impedance adapt to diverse signal sources and coupling requirements.