SR850 - Stanford Research Systems Lock-in Amplifiers

Stanford Research Systems SR850 Overview

The SR850 is a digital lock-in amplifier based on an innovative DSP (Digital Signal Processing) architecture. The SR850 boasts a number of significant performance advantages over traditional lock-in amplifiers—higher dynamic reserve, lower drift, lower distortion and dramatically higher phase resolution. In addition, the CRT display and 65,536 point memory make it possible to display and process data in a variety of formats unavailable with conventional lock-ins. At the input of the SR850 is a precision 18-bit A/D converter which digitizes the input signal at 256 kHz. The A/D converter, together with a high-speed DSP chip, replace the analog demodulator (mixer), low pass filters and DC amplifiers found in conventional lock-ins. Instead of using analog components, the SR850 is implemented by a series of precise mathematical calculations which eliminate the drift, offset, nonlinearity and aging inherent in analog components. The same DSP chip digitally synthesizes the reference oscillator providing a source with less than -80 dBc distortion, 100 mHz frequency resolution and 2 mV of amplitude resolution. Features: 1 mHz to 102.4 kHz frequency range >100 dB dynamic reserve 0.001 degree phase resolution Time constants from 10 µs to 30 ks (up to 24 dB/oct rolloff) Auto gain, phase, reserve and offset Data logging (up to 65k samples) Smoothing, curve fitting & statistics GPIB, RS-232 and 3.5" disk drive