DXA-001 102kHz Digital Lock-in Amplifier

Input Channel

 

With the low-noise analog pre-amplifier, the signal input of DXA-001 can be switched to operate in the single-ended or differential voltage mode, and the input noise is 10 nV/√Hz. The input impedance is 10 MΩ and the full-scale input voltage sensitivity ranges from 1 nV to 1V. Besides, DXA-001 can also be used for current measurements with variable current gains of 10^6 or 10^8 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 DXA-001 has an inherently large dynamic reserve up to 100dB. The sampling rate of 312.5KSPS is determined by a precision 24-bit A/D converter and a specific filter is designed to avoid aliasing.

 

Reference Channel

In order to provide the reference signal for DXA-001, an externally applied sine wave or square wave, 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 the digital phase-shifting technique, the reference signal phase could be adjusted with 0.01° resolution. The internal reference mode can operate at a fixed frequency from 1 MHz to 100 kHz. In addition, the external reference is also applicable to DXA-001, including the sinewave reference signal and TTL logic reference signal. The rising and trailing edge of the external reference signal are applied to trigger off the internal Phase Locking Loop (PLL). Based on the frequency of the reference signal, harmonic detection can be performed by DXA-001. The maximum frequency of the measurable harmonics is 32767 times of basic frequency, and it is also less than the maximum operational frequency of 100 kHz.

 

Display

DXA-001 uses the 5.6 inch 640×480 TFT color display as its screen. Data measured by DXA-001, 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.

 

 

Besides, DXA-001 can display polar plots, showing phasor composed of in-phase and quadrature components of the signal. All displays can be easily scaled by 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.

 

 

 

Simultaneous Multiple-harmonic Measurement

 

The traditional phase-locked amplifier can only measure fundamental frequency signal or one certain harmonic ware at the same time, so it can not meet the requirement in some occasions when measuring multiple frequency components simultaneously is needed. On the digital end, DXA-001 combined FPGA and ARM technology, which has wider processing bandwidth and a more flexible digital framework. The digital processing precision could reach 48 bits and could measure 3-channel harmonic components simultaneously, which makes one DXA-001 is equal to three traditional phase-locked amplifiers.

 

Remote Operation

 

The built-in RS232 to USB interfaces on DXA-001 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. The display menu offered by the LabVIEW program allows customers to observe all commands received and responses generated by the instrument.

 

Signal Channel

        Voltage input Mode                   Single-ended or Differential

        Full-scale Sensitivity                  1 nV to 1 V in a 1-2-5 sequence

                                                           1 fA to 1 µA

        Current input                             106 or 108 V/A
        Impedance
                Voltage                              10 MΩ
                Current                              1 kΩ to virtual ground
        C.M.R.R                                     >100 dB to 10 kHz, decreasing
        Dynamic reserve                        >120 dB
        Gain accuracy                            0.2% typ, 1% max
        Voltage Noise
                                                           5 nV/√Hz at 997 Hz
        Current Noise
                                                           5 fA/√Hz at 97 Hz
                                                           13 fA/√Hz at 997 Hz
        Line filters                                   50/60 Hz and 100/120 Hz
        Grounding                                     BNC shield can be grounded or floated via 10 kΩ to ground

 

Reference Channel

        Input
                Frequency range                1 mHz to 102 kHz
                Reference input                  TTL or Sine
                Input impedance                 1 MΩ
                Square reference level        V_IH>3V， V_IL<0.5V
                Sine reference signal          >1 Hz
                                                            > 400 mVpp
        Phase
                 Resolution                          0.001°
                 Absolute phase error          <1°
                 Relative phase error           <1 mdeg
                 Phase noise
                                                            Internal ref. Synthesized, <0.0001 deg at1 kHz
                                                            External ref. 0.001 deg at 1 kHz (100 ms time constant, 12 dB/oct)
                 Drift
                                                            <0.01 deg/℃ below 10 kHz
                                                            <0.1 deg/℃ above 10 kHz

        Harmonic detection                     2F, 3F, …nF to 102 kHz (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 sets

                Display                                 no zero drift on all sets

                Analog outputs                     <5 ppm/℃ for all dynamic reserve settings

        Harmonic rejection                     -90 dB

        Time constants                           10 µs to 3 ks (<200 Hz)

                                                           10 µs to 30 s (>200 Hz)

        Synchronous filters                     Available below 200 Hz(18, 24 dB/oct rolloff)

 

Internal Oscillator  

        Frequency                                 Range 1 mHz to 102 kHz

         Accuracy                                   2 ppm + 10 µHz

                Resolution                         1 mHz

        Distortion                                   -80 dBc (f<10 kHz)，-70 dBc (f>10 kHz)

        Amplitude                                   0.001Vrms to 5 Vrms ( Resolution:1 mVrms)

                Accuracy                            1%

                Stability                               50 ppm/℃

        Sine Outputs

                                                           Sine signal， output impedance 50 Ω

        TTL Outputs                               5V TTL/CMOS level， output impedance 200Ω

 

Display

        Screen                                       5.6 inch, 640×480 TFT

        Screen format                            Single or dual display

        Display quantities                       Each display shows one trace,

                                                            traces can be defined as X,Y,R,θ

        Display types                              Numerical form, bar graph, polar plot and strip chart

        

 

 

AUX Inputs and Outputs  

        CH1 and CH2 Outputs

                Function                             Output X, Y, R, θ

                Output Voltage                    ±10 V full scale.

                                                            30 mA max output current

                Update Rate                        312.5kHz

        AUX Inputs

                Function                             4 Channel Inputs

                Amplitude                           ±10 V，1 mV resolution ratio

                Impedance                         1 MΩ

        AUX Outputs

                Function                             4 Channel Outputs

                Amplitude                           ±10 V，1 mV resolution ratio

                Drive current                      ±25mA max

        Trigger Input

                Function                             TTL external trigger is used for data storage

        Monitor Output

                Function                             Analog output of a signal-amplifier

                Drive current                      ±40mA max

 

Interfaces

        RS-232 to USB interface,

        IEEE-488 interface(optional).

 

 

General

        Power requirements

                Voltage                                220~240 V AC

                                                            100~120 VAC(optional)

                Frequency                           50/60 Hz
                Power                                  30 W

        Power supply rejection                70dB@1MHz

        Weight                                         11 KG      

        Dimensions

                Width                                  448 mm

                Depth                                  513 mm

                      

                Height

                        With feet                     148 mm