SR830 Digital Lock-in Amplifier

Stanford SR830 Digital Lock-in Amplifier Frequency range 1 mHz to 102.4 kHz

Frequency range 1 mHz to 102.4 kHz
>100 dB dynamic reserve
Stability of 5 ppm/°C analog
Phase resolution of 0.01 degrees
Time constants from 10 μs to 30 s (up to 24 dB/octave rolloff) with auto gain, auto phase, auto reserve, and auto offset functions Synthesized reference source
GPIB and RS-232 interfaces

Overview of Features:
Input Channel
The SR810 and SR830 have a differential input noise of 6 nV/√Hz, an input impedance of 10 MΩ, and the minimum full-scale input can also be configured for current measurement with optional current gains of 10⁶ V/A and 10⁸ V/A. Single-line filters (50 Hz or 60 Hz) and double-line filters (100 Hz or 120 Hz) are used to eliminate line-related interference. Unlike traditional lock-in amplifiers, the SR810 and SR830 do not have tracking bandpass filters at the input. In conventional lock-in amplifiers, bandpass filters are used to improve dynamic reserve, but they also introduce noise, amplitude and phase errors, and drift. The SR810 and SR830 do not require bandpass filters due to their digital signal processing design, which inherently provides a large dynamic reserve.

High Dynamic Reserve
The dynamic reserve of a lock-in amplifier is defined as the ratio of the maximum noise signal to the full-scale input voltage range for a given input voltage range. The maximum noise signal refers to the amplitude of the largest signal across all frequencies that can overwhelm the input signal, making it impossible for the lock-in amplifier to measure the signal within the specified accuracy. Traditional lock-in amplifiers use analog demodulators to mix the input signal with the reference signal, limiting the dynamic reserve to around 60 dB and suffering from poor stability, output drift, excessive gain, and phase errors. In the SR810 and SR830, demodulation is achieved by sampling the input signal with a high-precision ADC and then multiplying the digitized input signal by a synthesized reference signal. This digital demodulation technique enables a dynamic reserve greater than 100 dB (without pre-filters) and avoids the errors associated with analog demodulation.