Stanford Research SR2124 Dual Phase Lock-in Amplifier

The Stanford Research SR2124 Dual Phase Lock-in Amplifier is a precision instrument for measuring small AC signals embedded in noise using all-analog design to eliminate digital interference. Operating across 0.2 Hz to 200 kHz, it achieves input sensitivity down to 100 nV full-scale with dynamic reserve to 80 dB - extendable to 100 dB with optional band-pass filtering. The instrument functions as either a lock-in amplifier or frequency-selective AC voltmeter, accepting both voltage and current inputs with selectable coupling modes.

Technical Specifications

• Frequency range: 0.2 Hz to 200 kHz


• Input sensitivity: 100 nV minimum full-scale


• Dynamic reserve: 80 dB (60 dB typical); up to 100 dB with optional input filtering


• Voltage input: Single-ended/differential FET preamplifier, 2.5 nV/√Hz noise floor, 10 MΩ input impedance


• Current input: Preamplifier with gains of 10⁶ V/A and 10⁸ V/A


• Reference output: Sine and square waveforms, amplitude 100 nV to 10 V


• Quadrant outputs: Four 1 Vrms sine waves at 0°, 90°, 180°, 270°


• Signal outputs: 1 µV to 20 Vpp into 10 kΩ load, 50 Ω output impedance


• Output time constants: 1 ms to 300 s, selectable –6 dB or –12 dB/octave rolloff


• Input filters: Flat, band-pass, high-pass, low-pass, notch with Q-factor 1–100


• AC/DC coupling: Both modes supported


• Grounding: Ground and Float modes

Key Features

• All-analog architecture eliminating digital noise sources


• Internal reference with ±0.1% accuracy


• External reference locking at f, 2f, or 3f with 100 mVpp minimum input


• Tunable narrow-band amplifier providing additional 60 dB rejection of out-of-band signals


• Two-stage output low-pass filtering with minimum time constant bypass


• Rear voltage-controlled oscillator (VCO) reference option


• Front and rear panel reference outputs

Typical Applications

• Low-temperature research requiring ultra-low noise performance


• Precision small-signal measurement in noisy environments


• Lock-in detection for phase-sensitive measurements


• AC signal characterization and frequency-selective analysis

Compatibility & Integration The SR2124 provides voltage and current input paths with independent coupling selection, front-panel reference output control, and multiple reference modes for flexible integration into measurement systems. Quadrant outputs enable external phase-shift applications.