SSI OE2041 Lock-In Amplifier 60MHz

Input Signal Channel

         The low-noise analog front-end amplifier in the OE2041 lock-in amplifier handles single-ended or differential signals with an equivalent input noise of 3.5 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 OE2041 achieves a dynamic range exceeding 120 dB and adjusts its internal programmable gain amplifier according to 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 OE2041 digital lock-in amplifier can be a sine wave or square wave selected according to the user's requirements, or an internally generated digital reference signal. When the OE2041 is set to internal reference mode, the internal high-precision oscillator and direct digital synthesis algorithm generate the sine wave used to multiply the input signal, and the internal reference is virtually immune to phase noise. Digital phase-shifting technology gives the internal reference a phase resolution of 0.001°. The internal reference mode operates over a frequency range from 1 mHz to 60 MHz. The OE2041 also supports an external reference mode, in which a sine wave or TTL logic level serves as the external reference. The rising or falling edge of the external reference triggers the internal phase-locked loop (PLL). Based on the reference frequency, the OE2041 can detect signal harmonics up to the 32,767th harmonic of the fundamental, provided the maximum harmonic frequency does not exceed the instrument's maximum measurement frequency of 60 MHz.

Digital Modulator and Output Filter

         The core component of the OE2041 is its modulator. Unlike 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 coherent signal within the digital modulator, calculation errors are minimized, ensuring the instrument can accurately detect weak input signals. The OE2041's time constant is adjustable from 30 ns to 4.4 ks. The output low-pass filter roll-off rate can be set to 6, 12, 18, 24, 32, 36, 42, or 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 OE2041 deliver higher dynamic reserve (>120 dB), precise phase (absolute phase error <1°), zero DC drift, and excellent quadrature compared with analog lock-in amplifiers. Furthermore, when the input signal frequency is below 200 Hz, the OE2041 can enable a synchronous filter to eliminate harmonic interference from the reference signal, ensuring fast detection of valid low-frequency signals.

Oscillator

         The internal oscillator of the OE2041 lock-in amplifier provides a low-distortion (–80 dBc) reference signal. The frequency of a single sine-wave reference signal can be varied from 1 mHz to 60 MHz, with a frequency resolution of 1 mHz. The frequency and amplitude of the internal oscillator's reference signal can be set via the OE2041 front panel or computer communication. When the instrument is set to external reference mode, the internal oscillator signal remains phase-locked to the external reference signal.

Signal Generator

         Built on a 16-bit digital-to-analog converter (DAC), the OE2041 generates sine waves from 1 mHz to 60 MHz. The output frequency is referenced to the instrument's internal oscillator, and the sine wave amplitude can be set through the instrument's control menu. The signal generator's maximum sine wave output is 1 Vrms with 1 µVrms resolution.

Display

         The OE2041 uses a 5.6-inch 640×480 TFT color display as its main screen. Measured data from the lock-in amplifier—such as X, Y, R, and θ values—can be displayed simultaneously as numeric readouts, bar graphs, and other formats.

Manual Operation

         The TFT LCD screen displays both measurement data and the instrument's control menus. 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 OE2041 digital lock-in amplifier automatically adjusts its operating parameters to achieve the optimal measurement mode for different input signals. Using the individual keys in the 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 functions, the instrument can easily measure the input signal under test.

PC Software Operation

         The OE2041 offers RS232, USB 2.0, and Ethernet interfaces, providing full control of all instrument functions so that users can effectively access every measurement capability from a host computer, including setting operating 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 OE2041 easy to integrate into complex scientific experiments.

Signal channels
    Voltage input mode                Single-ended or differential input
    Full-scale sensitivity度                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 60 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