Stanford Research SR865A (available for rent)
The Stanford Research SR865A Lock-In Amplifier redefines precision and performance, making it an invaluable tool for researchers and engineers alike. Known for its impressive capabilities and exceptional value, the SR865A is designed to meet demanding experimental requirements.
The front-end of the SR865A features both voltage and current input amplifiers that provide remarkable sensitivity. The voltage input employs a switchable single-ended/differential JFET-pair amplifier with an outstanding noise floor of 2.5 nV/√Hz at 1 kHz and under 10 nV/√Hz at 10 Hz. With a high 10 MΩ input impedance, it can be configured for AC or DC coupling. Optional user-selectable input connector shields can ground through either a 10 Ω (Ground) or 10 kΩ (Float) resistor.
The integrated current amplifier is a significant enhancement over previous models, offering a selectable input range of either 1 µA or 10 nA. The 1 µA setting boasts a bandwidth of 400 kHz with noise sensitivity at 130 fA/√Hz, while the 10 nA range operates at 2 kHz bandwidth with even lower noise at 13 fA/√Hz.
For advanced applications, the SR865A seamlessly integrates with a complete suite of specialized pre-amplifiers offered by Stanford Research, including the SR550, SR552, SR554, SR555, and SR556, all powered directly through the rear-panel preamp power port.
The simplicity of the SR865A is evident in its user-friendly design. The sensitivity setting determines the voltage (or current) needed for full-scale output without the complexity of a “dynamic reserve” equation. Users can easily select the appropriate sensitivity for their experimental needs, ensuring the smallest input range that avoids overload.
This feature provides an effective dynamic reserve, exemplified by a 10 nV sensitivity and a 300 mV input range, yielding an impressive dynamic reserve of approximately 150 dB.
Time constant options range from 1 µs to 30 ks with customizable roll-off rates of 6, 12, 18, and 24 dB/oct. The advanced digital filters significantly enhance measurement efficiency while also reducing noise. For time constants under 3 seconds, Gaussian FIR filters provide superior rise time and stopband attenuation. For longer time constants, linear phase IIR filters deliver rapid settling times with equivalent attenuation.
Exclusive to the SR865A, synchronous filtering is selectable at reference frequencies below 4 kHz, effectively eliminating undesired harmonics without sacrificing output resolution.
The specified reference frequency range is extensive, spanning from 1 mHz to 4 MHz, with detection capabilities at the fundamental frequency and up to the 99th harmonic. Multiple reference modes are available, including internal mode for utilizing the SR865A’s precision oscillator, external mode for synchronizing with an external sine or TTL signal, and dual mode for detecting differences between internal and external signals. The chop mode facilitates the synchronization of optical choppers through a digital PID controller, minimizing frequency drift.
The SR865A also features a precision sine wave output with six-digit frequency resolution and an amplitude range spanning from 1 nV to 2 V. This output can be configured as a single-ended or differential signal, and accommodates a DC offset of up to ±5 V. A rear-panel logic-level sync signal is also available.
For external synchronization, the SR865A is equipped with 10 MHz input and output connections, allowing the unit to lock onto frequency references or synchronize multiple devices.
Designed for dual-channel analysis, the SR865A is equally adept in time-domain and frequency-domain applications. Its FFT display allows users to visualize the spectrum of input signals, enhancing diagnostic capabilities for detecting elusive noise sources.
The highlights of the SR865A’s interface include a full-color 640 x 480 touchscreen, configurable to display up to four data channels with options for large numeric results, strip-chart views, and real-time measurements, ensuring ease of use even from a distance. Key operational parameters are always visible, and a convenient HDMI port allows the touchscreen to be mirrored on external monitors.
Despite its comprehensive touchscreen interface, the SR865A maintains traditional usability through dedicated front panel knobs for commonly accessed controls, ensuring persistence in productivity across different user preferences.
Connectivity is robust, with GPIB, RS-232, USB, and Ethernet (VXI-11 and telnet) enabling versatile control options. A webserver interface provides seamless remote operation, with compatibility for monitoring and controlling from iOS devices via a dedicated app. Furthermore, the front-panel USB allows users to save data and screenshots directly to flash drives in various formats, accommodating needs for documentation and reporting.
- Frequency Range: 1 mHz to 4 MHz
- Low Noise Voltage and Current Inputs
- Time Constants: 1 µs to 30 ks
- Touchscreen Data Display with Multiple Viewing Options
- 10 MHz Timebase Input and Output
- Multiple Remote Interfaces: GPIB, RS-232, Ethernet, USB
