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@100 kHz. The input impedance is 50 Ω or 10 MΩ and the full-scale input voltage sensitivity ranges from 1 nV to 1V. 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 120dB. The sampling rate of 250MSPS 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 externally applied sine wave or square wave, or its owninternally 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 phase-shifting technique, the reference signal phase could be adjusted with 0.001° resolution. The internal reference mode can operate at a fixed frequency from 1 mHz to 60 MHz. In addition, the external reference is also applicable to OE2041, including the sinewave reference signal and TTL logic reference signal. The rising and trailing 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 also less than the maximum operational frequency 60 MHz.
Digital Demodulator and Output Filter
The key component of the OE2041 is the digital demodulator. Compared to traditional analog lock-in amplifiers, the OE2041'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. Time constants of the output low-pass filter from 30 ns to 4.4 ks can be selected with a choice of 6,12, 18, 24, 30, 36, 42 and 48 dB/oct rolloff. This low-pass digital filter is implemented using a high performance digital filter with a sample rate of 250 MHz. The digitaldemodulation and the low-pass filter used in OE2041 guarantees a high dynamic reserve (>120dB), accurate phase (absolute phase error <1 deg). Moreover, when the frequency of the input signal is lower than 200 Hz, A synchronous filter can be used to eliminate the harmonic influence of the reference signal, ensuring that OE2041 can detect a lowfrequency signal quickly and effectively.
Display
OE2041 has a 5.6-inch 640 x 480 color TFT-LCD. The measurement results of OE2041, such as X, Y, R, and θ, are shown in numerical form and bar graph on the display.In X-Y chart, OE2041 shows the trend of measurement results over time, and check the value by using knob control cursor.
Remote Operation
Users can use PC to control OE2041 through communication interfaces, including setting the parameters and reading the measurement data. OE2042 is equipped with a freeLabVIEW program, which makes it easy to use in complex scientific experiments.
Lock-in Amplifier
Parametric Sweeper
PID Controllers
FFT Spectrum Analyzer
Oscilloscope
