SSI OE2031 Lock-in Amplifier 10MHz

Input Signal Channel

         The low-noise analog front-end amplifier in the OE2031 lock-in amplifier handles single-ended or differential signals effectively, with an equivalent input noise of 6 nV/√Hz at 100 kHz. The channel offers an input impedance of 50 Ω or 10 MΩ and can detect input signal levels from 1 nV to 1 V at full-scale output. The OE2031 achieves a dynamic range exceeding 120 dB and adjusts its internal programmable gain amplifier according to the input signal amplitude to vary the overall dynamic reserve. A high-precision 14-bit ADC samples at 250 MSPS, and the anti-aliasing filter ahead of the ADC effectively prevents signal aliasing.

Reference Signal Channel

         The reference signal of the OE2031 digital lock-in amplifier can be a sine wave or square wave selected to suit the user's application, or an internally generated digital reference signal. In internal reference mode, the instrument's high-precision oscillator and direct digital synthesis algorithm generate the sine wave multiplied with the input signal, and this internal reference is virtually free of phase noise. Digital phase-shifting technology gives the internal reference a phase resolution of 0.001°. Internal reference mode operates over a frequency range from 1 mHz to 10 MHz. The OE2031 also supports external reference mode, accepting either a sine wave or a TTL logic level. The rising or falling edge of the external reference triggers the internal phase-locked loop (PLL). Based on the reference frequency, the OE2031 can detect signal harmonics up to the 32,767th order of the fundamental, provided the maximum harmonic frequency does not exceed the instrument's maximum measurement frequency of 10 MHz.

Digital Modulator and Output Filters

         The core component of the OE2031 is its modulator. Compared with analog signal multipliers, the instrument's internal digital modulator effectively suppresses potential measurement errors caused by DC offset and drift. In addition, by optimizing the multiplication of the internal coherent signal within the digital modulator, computational error is minimized, ensuring the instrument can accurately detect weak input signals. The time constant of the OE2031 can be set from 10 ns to 4.4 ks. The roll-off rate of the output low-pass filter can be set to 6, 12, 18, 24, 32, 36, 42, and 48 dB/octave. This low-pass digital filter is implemented using an infinite impulse response (IIR) filter structure, with a signal processing sampling rate of 250 MHz. The digital modulation method and filter architecture employed in the OE2031 ensure higher dynamic reserve (>120 dB), accurate phase (absolute phase error <1°), zero DC drift, and excellent quadrature performance compared with analog lock-in amplifiers. In addition, when the input signal frequency is below 200 Hz, the OE2031 can enable a synchronous filter to eliminate harmonic effects from the reference signal, ensuring fast detection of valid low-frequency signals.

Oscillator

         The internal oscillator of the OE2031 lock-in amplifier provides the instrument with a low-distortion (–80 dBc) reference signal. The frequency of the single sine-wave reference signal can be varied from 1 mHz to 10 MHz, with a frequency resolution of 1 mHz. Using the OE2031 front panel or computer communication, the frequency and amplitude of the reference signal generated by the internal oscillator can be set. When the instrument is set to external reference mode, the signal generated by the internal oscillator remains phase-locked to the external reference signal.

Signal Generator

         Based on a 16-bit digital-to-analog converter (DAC), the OE2031 can generate sine-wave signals in the frequency range from 1 mHz to 10 MHz. The signal frequency is referenced to the instrument's internal oscillator, and the amplitude of the generated sine wave can be set through the instrument's control menu. The maximum amplitude of the sine-wave signal that the OE2031 signal generator can produce is 1 Vrms, with a resolution of 1 µVrms.

Display

         The OE2031 uses a 5.6-inch 640×480 TFT color display as its main screen. The lock-in amplifier can simultaneously display measured data—such as the signal's X, Y, R, and θ values—as numeric readouts and bar graphs.

Manual Operation

         In addition to displaying measurement data, the TFT LCD also serves as the instrument's control menu. Using the soft keys around the main screen together with the numeric keypad on the front panel, users can efficiently adjust operating parameters such as the input signal measurement mode, reference mode, internal oscillator frequency, sine output amplitude, and display format.

Auto Functions

         The OE2031 digital lock-in amplifier automatically adjusts its operating parameters to select the optimal measurement mode for different input signals. Using the individual keys in the instrument's control menu, users can conveniently adjust the overall gain, the phase of the internal reference signal, the dynamic reserve, and the display scaling. With these auto-adjustment functions, the instrument can easily measure the input signal under test.

PC Software Control

         The OE2031 features RS232, USB2.0, and Ethernet interfaces, enabling full control of all instrument functions so that users can effectively access every measurement capability of the OE2031 from a host computer, including setting appropriate control parameters and reading measured data. To make these functions even easier to use, the instrument comes with a dedicated LabVIEW program that reads and saves measurement data in real time, making the OE2031 easy to integrate into complex scientific experiments.

Signal channels
    Voltage input mode                Single-ended or differential input
    Full-scale sensitivity                1 nV to 1 V, stepping in 1-2-5 multiples
    Input impedance                    Configurable 50 Ω//5 pF or 10 MΩ//5 pF, AC or DC coupling
    Common-mode rejection ratio                  >70 dB to 100 Hz, >50 dB to 100 kHz
    Dynamic reserve                    >120 dB

    Gain accuracy                    Standard 0.2% (<1MHz), max 3%

    Noise performance

        At 99.99 kHz              3.5 nV/√Hz

    Input shield grounding                BNC (A, B) shield can be directly grounded or connected to floating ground through a 1 kΩ resistor

Reference channel
    Input
        Frequency range                1 mHz to 10 MHz
        Reference input                Square wave or sine wave
        Input impedance                1 MΩ
        Square-wave reference level           

Scanning microscope            AFM, STM, SPM

Materials science                Carrier mobility, carrier density, Hall effect, ultrasonic materials

Transport measurement                Conductance measurement, impedance measurement

Noise characterization                Noise density, cross-correlation measurement

Optical experiments                Spectral analysis, spectral measurement, THz measurement, TDLAS

Sensor measurement            Gyroscopes, photoelectric sensors, resonators, accelerometers

Magnetic Sensing                SQUIDs, NV centers, atomic magnetometers, VSM

Biomedical                Microfluidics