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OE2041

30MHz Ultra-high Speed Lock-In Amplifier

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Characteristics


  • 10mHz to 30MHz frequency range
  • A high-performance signal generator
  • 1nV to 1V full-scale sensitivity
  • 3us to 3ks time constants
  • >80 dB dynamic reserve
  • Automatic adjustment
Overview
Now OE2041 DSP Lock-In Amplifier is the newest product of core technology with high performance. Based on the digital demodulation, output filter and high-precision stabilized 14-bit ADC, it is ideal to detect the weak signals,which are overwhelmed by greatly larger noise components. And OE2041 could measure the magnitude and phase of a signal simultaneously. It could be comparable with the international leading technology in some core parameters, like accuracy of measurement, range of operating frequency, SNR, dynamic reserve and so on making this DSP Lock-In Amplifier could meet the needs of scientific research and industrial purposes.
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Input Channel

With the low-noise analog pre-amplifier, the signal input of OE2041 can be switched to operate in the single-ended or differential voltage mode, and the input noise is 6 nV/√Hz@100kHz. The input impedance is 50Ω or 10 MΩ and the full-scale input voltage sensitivity ranges from 1 nV to 1V. Besides, OE2041 can also be used for current measurements with variable current gains of 10 V/A. Two line filters (50/60 Hz and 100/120 Hz) are designed to eliminate line related interference. The programmable gain amplifier is provided to adjust the dynamic reserve of the system according to the magnitude of the input signal, so that OE2041 has inherently large dynamic reserve up to 80dB. The sampling rate of 98.75MSPS is determined by a precision 14-bit A/D converter and a specific filter is designed to avoid aliasing.
Reference Channel

In order to provide the reference signal for OE2041, an external sine or TTL signal, or its own internally synthesized reference source could be used. When the instrument is set to internal reference mode, the internal precision stabilized oscillator and the digital synthesized algorithm are used to generate sinewave output that multiplies the input signal, there is virtually no reference phase noise when choosing internal reference mode. Taking advantage of digital phaseshifting technique, the reference signal phase could be adjusted with 0.01° resolution. The internal reference mode can operate at a fixed frequency from 10 mHz to 30 MHz. In addition, the external reference is also applicable to OE2041, including the sinewave reference signal and TTL logic reference signal. The rising and falling edge of external reference signal are applied to trigger off the internal Phase Locking Loop (PLL). Based on the frequency of reference signal, harmonic detection can be performed by OE2041. The maximum frequency of the measurable harmonics is 32767 times of basic frequency, and it is limited to the maximum operational frequency 30MHz.
Digital Demodulator and Output Filter

The core of Lock-In Amplifier OE2041 is demodulator. This digital demodulator could be effectively immune from the potential errors caused by DC drift and offset found in analog multipliers or switches. The coherent signal multiplication has been optimized for very low calculation error. The time constants of OE2041 could be configured extending from 3 ?s to 3 ks. The roll-offs of the output low-pass filter on OE2041 are 6, 12, 18, 24, 30 and 36 dB/octave. This low-pass filter is carried out by the architecture of digital infinite impulse response (IIR) filters and updated at 98.75MHz signal sampling rate. The advantages of this design over
common analog instruments are higher dynamic reserve (>80dB), accurate phase shifts (absolute phase error <1°), zero drift, and orthogonality. Meanwhile, below 200 Hz, OE2041 can perform synchronous filtering, which is used to notch out multiples of the reference frequency. This function ensures that OE2041 works quickly at low frequency.

Internal Oscillator

The internal oscillator helps to generate a very low distortion (–80 dBc) reference signal. The single frequency of sine waves can be extended from 10 mHz to 30MHz while the resolution generated is 0.1 mHz. Both frequency and amplitude can be set from the front panel or a computer. When choosing external reference mode, the internal oscillator is phase-locked to the external reference signal.

Signal Generator

OE2041 generates one sinusoidal signal in range from 10mHz to 30MHz, using 14-bit D/A converter. The frequency and phase shift of this sinusoidal signal are corresponding to that of the internal reference signal, and its amplitude could be set with control menu. The maximum amplitude provided by signal generator is 1Vrms with 1mVrms accuracy.

Display

OE2041 uses the 5.6 inch 640×480 TFT color display as its screen. Data measured by OE2041, such as, X, Y, R, θ, is stored in up to four traces. Trace values can be displayed as a bar graph or as a strip chart showing the trace values as a function of time.

OE2041 can also show the relationship of time and range in a XY graph and you can check the value of sampling point by using knob control cursor.

Besides, OE2041 can display polar plots, showing phasor composed by in-phase and quadrature components of the signal. All displays can be easily scaled by the manual operation, and the auto-scale feature is available to optimize display quickly. The screen can be configured as a single large display, or two horizontally-split displays.

Manual Operation

In addition to displaying data, the color TFT display panel is also used to display the control menu. In conjunction with keys grouped around the screen and numeric keypad, customers could adjust instrument's parameters effectively, such as oscillator frequency, which can be set to a fixed value and to a high precision.
Auto Function

OE2041 has the ability to adjust measurement parameters to optimum setting for input signal. Gain, phase, dynamic reserve and display scaling could all be set with different independent key presses from the control menu. With this function, the input signals could be measured easily and automatically.
Remote Operation

The built-in RS232 to USB interfaces on OE2041 allow full manual operation from a controlling computer, including setting or interrogating control and reading out data. Free LabVIEW program is provided. It makes it easy to set up and run complex experiments, such as remote control of every instrument function and save the data. The display menu offered by the LabVIEW program allows customers observe all command received and responses generated by instrument.


Signal Channel
Voltage input Mode         Single-ended or Differential
Full-scale Sensitivity             1nV to 1 V in a 1-2-5 sequence
Current input             106 V/A
Impedance
        Voltage      50Ω or 10 MΩ // 25pF, AC or DC coupled
        Current      1kΩ to virtual ground
C.M.R.R           >80 dB to 10 KHz, decreasing by 6 dB/oct
Dynamic reserve              >80 dB
Gain accuracy0.5% typ, 2% max
Noise6nV/√Hz at 100 kHz

0.13pA/√Hz at 1 kHz

0.013pA/√Hz at 100 Hz
Reference Channel   
Input
        Frequency range     10 mHz to 30MHz
        Reference input   TTL or sine
        Input impedance      1 MΩ//25 pF
Phase
        Resolution        0.01° increments
        Absolute phase error    <1°
        Relative phase error   <0.01°
Orthogonality90°±0.001°
        Internal ref.      Synthesized, <0.0001°rms at 1kHz
        External ref.      0.005°rms at 1 kHz (100 ms time constant, 12 dB/oct)
Harmonic detection              2F, 3F, …nF to 100kHz (n<32,767)
Acquisition time
        Internal Ref.  Instantaneous acquisition
        External Ref.      (2 cycles + 5 ms) or 40 ms, whichever is larger
Demodulator
Stability      
        Digital outputs      no zero drift on all setting
        Display         no zero drift on all setting
        Analog outputs      <5 ppm/℃ for all dynamic reserve settings
Harmonic rejection -90 dB
Time constants3us to 3ks (<200Hz)

3us to 30s (>200Hz)  (6, 12, 18, 24 dB/oct rolloff)
Synchronous filtersAvailable below 200 Hz and 18,24 dB/oct
Display
Screen5.6 inch, 640×480 TFT
Screen format                Single or dual display
Display types               Large numeric readout, bar graph, polar plot and strip chart
Internal Oscillator
Frequency
        Range          10 mHz to 30 MHz
        Accuracy           25 ppm + 30 MHz
        Resolution        1 mHz
Distortion-80 dBc (f<10 kHz), -70 dBc (f>10 kHz)
Amplitude                  0.001 to 100 Vrms
Interfaces
RS-232 to USB interfaces           All instrument functions can be controlled and read through USB interfaces.