Overview

The OE2031 is a high-frequency phase-locked amplifier offering exceptional measurement capabilities for both weak signals and wide bandwidths, with a bandwidth measurement range of DC to 10MHz. With the advantage of the latest digital signal processing technology and high-speed 250MSPS 14-bit ADC, OE2031 can easily detect the phase and the magnitude of weak signals overwhelmed by various large noise. The performance of OE2031 is as good as other lock-in amplifiers all over the world, even better than them in some certain parameters, such as measurement accuracy, SNR, dynamic reserve, which meets the needs of scientific research and industrial application well.

Input Channel

OE2031 detects an input signal in a single-ended mode or a differential voltage mode. With an ultra low-noise pre- amplifier, the input noise is as low as 3 nV/Hz@1MHz. The input impedance is 50Ω or 10MΩ and the full-scale input voltage sensitivity ranges from 1nV to 2 Vrms. Besides, designed to eliminate power frequency interference. A programmable gain amplifier is used to adjust the dynamic reserve of the system, so that OE2031 can keep a high dynamic reserve of 120 dB. The high-precision 14-bit ADC has a sampling rate of 250 MSPS, and the excellent anti- aliasing filter (Blocking Attenuation >100dB) in front of the ADC can effectively prevent signal aliasing.

Reference Channel

The reference signal can work in external mode or internal mode. In internal mode, a precise and stable internal oscillator generates sine wave as an internal reference that is multiplied by the input signal. This internal signal is without any phase noise. With the digital phase-shifting technique, the phase resolution of the reference signal is 0.001deg. OE2031 can work at any fixed frequency from DC to 10MHz in this mode.In external mode, the reference signal can be a sine wave or a TTL pulse or square wave. The rising or falling edge of the external reference signal triggers the Phase Lock Loop (PLL) to lock the external signal. Based on the frequency of the reference signal, can demodulate multiple harmonics and arbitrarily frequency input signal. The maximum harmonic signal frequency can reach 10000 times the fundamental frequency, and the maximum harmonic frequency cannot exceed the maximum operating frequency of the instrument by 10MHz.

Digital Demodulator and Output Filter

The key component of the OE2031 is the digital demodulator. Compared to traditional analog lock-in amplifiers, OE2031's internal digital demodulator effectively rejects the measurement errors caused by DC drift and offset. In addition, by optimizing the multiplication of the internal coherent signal of the digital demodulator, the calculation error is minimized so that the instrument can accurately detect the input weak signal. OE2031 features 6 dual-phase demodulators. Time constants of the output low-pass filter from 100ns to 3ks (50μHz to 1.6MHz) can be selected with a choice of 6, 12, 18, 24, 30, 36, 42 and 48 dB/oct rolloff (1st to 8th order). This low-pass digital filter is implemented using a high performance digital filter with a sample rate of 250 MHz . The digital demodulation and the low-pass filter used in OE2031 guarantees a high dynamic reserve (>120dB), accurate phase (absolute phase error < 1deg). Moreover, when the frequency of the input signal is lower than 1MHz, A synchronous filter can be used to eliminate the harmonic influence of the reference signal, ensuring that OE2031 can detect a low- frequency signal quickly and effectively.

Auxiliary IO

The OE2031 features arbitrary auxiliary input and output interfaces. The AUX-IN port can measure voltages below 10V at a sampling rate of 312.5kSPS. The AUX-OUT/CH-OUT port operates at a refresh rate of 1 Msps, capable of outputting X, Y, R and θ-values, and arbitrary DC voltages. Additionally, the OE2031 incorporates CLK-IN, CLK-OUT, TRIG IN, TRIG OUT, and analogue mirror output ports.

Signal Generator

The OE2031 utilises a 16-bit high-precision digital-to-analogue converter (DAC) to output a sinusoidal signal matching the internal reference frequency. This sinusoidal wave features a maximum amplitude of 2Vrms, an accuracy of 0.1μVrms, and a frequency range spanning DC to 10MHz. The amplitude and phase of the output sine wave can be configured via the OE2031 display.

Internal Oscillator

The two internal oscillators of the OE2031 generate low-distortion (-75dBFS) sine reference signals from DC to 10 MHz/80 MHz, with frequency resolution up to 1 nHz. The frequency and amplitude of the reference signal can be set via the OE2031 front panel or communication interface. When the OE2031 is configured in external reference mode, the internal reference signal locks to the external reference signal.

Display

The OE2031 is equipped with a 5.6-inch TFT-LCD colour display serving as the primary interface for the instrument, enabling comprehensive independent control via the keyboard. Data detectable by the instrument, such as signal X, Y, R and θ-values, can be displayed through numerical graphs, bar charts, and full data presentation modes.

Manual Operation

The OE2031 can use the softkeys on the front panel, together with the knobs, to realize convenient and quick parameter adjustments, such as adjusting the frequency and phase of the internal reference signal.

Auto Function

The OE2031 can automatically adjust to different optimal operating states based on the input signal, such as automatic range adjustment, automatic filter parameter setting, automatic phase compensation adjustment, and automatic output bias adjustment.

Communication Interface

The OE2031 has USB2.0, Gigabit Ethernet port and standard 9-pin RS232 serial port. Through these interfaces, users can effectively utilize all testing functions of the OE2031 on a controlling computer, setting reasonable control parameters and reading the data measured by the instrument.