SR860 lock-in amplifier

SR860 lock-in amplifier

SR860 lock-in amplifierparameters

• 1 mHz to 500 kHz

• Touch screen data display

• 1 µ s to 30 ks time constant

• Low noise voltage and current input

• High bandwidth output

• HDMI video output

• 10 MHz time base input and output

• GPIB、RS-232、 Ethernet and USB

Excellent performance. They are your expectations for the Stanford Research System lock-in amplifier. They are provided by the new SR860 lock-in amplifier, which is a new product in the SRS innovative lock-in series. SR860 has analog performance, complex new digital signal processing capabilities, intuitive user interface, and a wide range of computer connectivity options, making it an ideal choice for any synchronous detection application.

With over 30 years of experience in lock design, SRS has made every effort to optimize every detail of the SR860. From heavy-duty toroidal transformers that eliminate switch mode noise to iOS connections that lock your phone, to DSPs that eliminate more noise while speeding up experimentsfilteringThe device.

Lock in amplifier signal input

trend chart

Locking performance starts from the front-end. The SR860 front-end provides voltage and current input amplifiers. The voltage input is a switchable single ended/differential JFET pair amplifier with a noise of 2.5 nV/√ Hz at 1 kHz and below 10 nV/√ Hz at 10 Hz. The voltage input has an input impedance of 10 M Ω and can be AC or DC coupled. The input connector shield can be connected to instrument ground through a user selectable 10 Ω (ground) or 10 k Ω (floating) resistor.

The built-in current amplifier of SR860 has made significant improvements compared to previous designs. The current input range can be selected from 1 μ A or 10 nA. The 1 μ A range has a bandwidth of 400 kHz and noise of 130 fA/√ Hz, while the 10 nA range provides a bandwidth of 2 kHz and noise of 13 fA/√ Hz.

Although the built-in voltage and current amplifiers are suitable for most applications, the SR860 is also compatible with the full range of dedicated preamplifiers provided by SRS. SR550 (FET input), SR552 (BJT input), SR554 (transformer input), SR555 (120 kHz current amplifier), and SR556 (low-noise current amplifier) can all be powered directly from the power port of the SR860's rear panel preamplifier.

Sensitivity and input range

Bar chart recording

Like previous instruments, the sensitivity setting of SR860 is to generate a full-scale output voltage (or current). But unlike previous designs, the input range of SR860 can be clearly set from the front panel without reference to the confusing "dynamic reserve" equation. Just select the sensitivity required for your experiment, and then choose the min input range that will not overload. nothing more.

The effective dynamic reserve of SR860 is the ratio of these two settings. For example, for a sensitivity setting of 10 nV and an input range of 300 mV, the effective dynamic reserve of SR860 is 3 × 10 7, or close to 150 dB.

Constant output time of lock-in amplifier

SR860 provides traditional RC response output time constants ranging from 1 µ s to 30 ks, with roll offs of 6, 12, 18, and 24 dB/OCT. But in addition, SR860 also provides digital filters that can significantly shorten measurement time while improving signal-to-noise ratio. Below 3 seconds, the filter is a Gaussian FIR filter, which has significantly better rise time and stopband attenuation at the same noise bandwidth as an RC filter. These filters also have symmetrical rising and falling contours, which can preserve the characteristic shape during frequency scanning. At a time constant exceeding 3 seconds, the filter is a linear phase IIR filter, and under equivalent stopband attenuation, its stable speed is almost twice that of an RC filter.

Synchronous filtering can also be selected at reference frequencies below 4 kHz. The synchronous filter cuts out multiples of the reference frequency and is very useful for low-frequency measurements, otherwise multiples of the reference frequency may appear in the locked output. Unlike previous designs, the synchronous filter in SR860 can be selected without sacrificing output resolution.

Lock in amplifier reference channel

The designated reference frequency range for SR860 is 1 mHz to 500 kHz. The detection can be performed at the fundamental frequency of the reference frequency or up to the 99th harmonic. There are several reference modes available: the internal mode uses the precision internal oscillator of SR860 as a reference. externalMode lockTo external sine signals or TTL signals. In dual-mode, locking detects the difference frequency between the internally set reference frequency and the externally applied synchronization signal, allowing for direct recovery of the dual modulation signal. In chopping mode, the SR860 provides a digital PID (Proportional Integral Derivative) controller signal to synchronize the SR540 chopper with a locked internal oscillator By directly controlling the chopper through locking, frequency drift can be almost eliminated.

Sine output

SR860 provides precise sine wave output, with a frequency resolution of 6 digits and an amplitude range of 1 nV to 2 V. The unique feature of SR860 output is that it can be configured as a single ended or differential (balanced) signal. A DC offset of up to ± 5 V can be applied to sinusoidal output. It also provides a rear panel logic level synchronization signal that is synchronized with the sine output.

time base

Provide 10 MHz input and output on the rear panel, allowing SR860 to lock to external frequency references (such as FS725 10 MHz rubidium frequency standard). Alternatively, the 10 MHz output of SR860 can be used to synchronize multiple locking or other testing devices with a 10 MHz time base input.

FFT display

FFT analysis

Lock in amplifiers are traditionally time-domain instruments, but sometimes it is easier to understand signals in the frequency domain. SR860 is a common occurrence here. FFT displays the frequency spectrum of the front-end input signal, the frequency spectrum of the signal after the mixer, or the frequency spectrum of the signal after the time constant filter. Using FFT display can simplifytrackSneak noise sources, otherwise these noise sources will be lost in the "odd" output of traditional lock-in amplifiers.

Touch screen display

SR860 front panelmiddleIt is a full-color 640 × 480 touch screen that can be set to display up to 4 data channels. When a dark laboratory is needed, the LCD screen can be set to blank from the front panel or remote interface. ）Each data channel can be configured to display X, Y, R, Θ, Aux In (1-4), Aux Out (1-2), X noise, Y noise, sine amplitude, sine output DC level, reference phase or reference frequency. The screen can be set to display data channels as large numbers that are easily visible from the entire room, or as a "bar chart" display that shows the complete history of each channel, with a selectable time range from 0.5 s/div to 2 days/zone. Even if the measurement values are not displayed, SR860 always saves all measurement values to ensure that no data is lost. The touch screen also continuously displays key lock setting parameters, such as phase, reference frequency, and sine amplitude. The rear panel HDMI port allows viewing LCD screens on any HDMI monitor or TV.

digital readout

It should be emphasized that although touch screen displays are used to display data, there is no need to use touch screens to control common instrument functions on the SR860. All commonly used controls, such as time constant, reference frequency, sine amplitude and offset, input configuration, etc., can be controlled through dedicated front panel knobs or buttons. The menu displayed on the touch screen allows access to infrequently accessed configuration settings, such as TCP/IP settings and other communication settings.

computer connection

SR860 comes standard with almost all imaginable remote interfaces. Of course, GPIB (IEEE488.2) and RS-232 are provided, as well as USB (Test and Measurement Class) and Ethernet (VXI-11 and telnet). SR860 has its own network server and can remotely monitor and control instruments with just one browser.

The front panel USB port allows data and screenshots to be transferred to a USB flash drive. Data can be saved as comma separated files or MATLAB compatible MAT file. Merging screenshots and data into reports or spreadsheets has never been so simple.

Specification parameters of lock-in amplifier

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