SR830 Lock-In Amplifier with 1 mHz to 102.4 kHz Range, 5 ppm/°C Stability, and 0.01 Degree Phase Resolution

The SRS Stanford Research Systems SR830 Lock-In Amplifier delivers high performance at a reasonable cost. This instrument simultaneously displays signal magnitude and phase while utilizing digital signal processing (DSP) to replace conventional lock-in components like demodulators, output filters, and amplifiers. The SR830 offers uncompromised performance with an operating range of 1 mHz to 102 kHz and 100 dB of drift-free dynamic reserve.

• 1 mHz to 102.4 kHz frequency range
• >100 dB dynamic reserve
• 5 ppm/°C stability
• 0.01 degree phase resolution
• Time constants from 10 µs to 3 ks (up to 24 dB/oct rolloff)
• Auto-gain, -phase, -reserve & -offset functions
• Integrated reference source
• GPIB and RS-232 interfaces

The SR830 Lock-In Amplifier features differential inputs with 6 nV/√Hz input noise. With an input impedance of 10 MΩ and minimum full-scale input voltage sensitivity of 2 nV, the input can also be configured for current measurements with selectable current gains of 10⁶ and 10⁸ V/A. Line filters (50 Hz or 60 Hz) and 2× line filters (100 Hz or 120 Hz) eliminate line-related interference. Unlike conventional lock-in amplifiers, no tracking band-pass filter is needed at the input, eliminating noise, amplitude and phase error, and drift.

The SR830 achieves more than 100 dB of true dynamic reserve (without prefiltering) through digital demodulation techniques. This approach samples the input signal with a high-precision A/D converter and multiplies the digitized input by a synthesized reference signal, eliminating errors associated with analog instruments.

Digital signal processing enables time constants from 10 µsec to 30,000 s with rolloff options of 6, 12, 18 and 24 dB/oct. For low frequency measurements (below 200 Hz), synchronous filters notch out multiples of the reference frequency, allowing effective output filtering with shorter time constants.

Analog phase shifting circuits are replaced with DSP calculations, providing phase measurement with 0.01° resolution and orthogonal X and Y outputs to 0.001°.

The built-in direct digital synthesis (DDS) source generates low distortion (-80 dBc) reference signals from 1 mHz to 102 kHz with 4½ digits of resolution. Both frequency and amplitude can be set from the front panel or computer interface.

Auto-functions optimize gain, phase, offset, and dynamic reserve with single key presses. Offset and expand features facilitate examination of small signal fluctuations, while harmonic detection extends to any harmonic (2F, 3F, ... nF) up to 102 kHz without changing reference frequency.

The SR830 includes user-defined outputs for measuring various parameters, X and Y analog outputs updated at 256 kHz, four auxiliary inputs (16-bit ADCs) for general purpose use, and four programmable outputs (16-bit DACs) providing voltages from -10.5 V to +10.5 V.

Two 16,000 point buffers enable simultaneous recording of two measurements, with data transfer via computer interfaces. An external trigger input synchronizes data recording.

All instrument functions are accessible through the front-panel keypad with a spin knob for parameter adjustment. Nine instrument configurations can be stored in non-volatile RAM for quick setup. Standard RS-232 and GPIB interfaces provide comprehensive computer control.