Products » Lock-In Amplifiers

µLIA-320: Standalone Lock-in Amplifier with USB interface

This is a dual-phase USB 2.0 compliant demodulator with streaming analog-to-digital (x, y) samples of the demodulated signal, for use in general applications where the measured signals are weak and noisy. An economical alternative to high-end lock-in amplifiers, specifically designed for high-channel-count OEM applications. The µLIA-320 is also well-suited for undergraduate & graduate physical-science lab experiments.

Our Rev. E µLIA-320 USB lock-in amplifiers are now available! Featuring more dynamic range, improved accuracy, wider operating-temperature range, and analog sinusoidal Reference Output capability. Contact us for further details.

• Dual-phase signal recovery to 400 kHz
• Native full-speed USB 2.0 compliant; multiple µLIA-320 instances supported on bus
• Continuous real-time streaming of demodulated samples, or readings-on-demand
• Flexible 32-bit DDS-based reference channel can act as input or output; can recover signals conventional quadrature lock-in's cannot
• Software-selectable analog monitor output enables standalone mode
• Intuitive uLIA-320 Panel host application (source code provided) for Windows 10 and Windows 7
• uLIA_dd device-driver toolkit (source code provided) for application programming in Visual Studio C/C++
• uLIA_dd device-driver standalone .DLL (source code provided) for application programming in LabVIEW, Python, & other languages
• Lightweight, miniature 5.6 x 7.2 x 1.7 in. form-factor in blue anodized chassis
• Separate international triple power supply

µLIA-320 Specifications
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See our µLIA-320 FAQ section below for frequently-asked questions about this product! All user manuals & downloads are accessible from the Support page of our web site. If you would like to review this material, please contact us and we will provide log-in information.

µLIA-321: Application-specific Lock-in Amplifier

A customized version of the µLIA-320, intended for OEM applications. Please contact us with your exact application needs.

• Single or dual phase
• USB or RS-232 interfaces
• Custom front-end & back-end filtering options available
• Custom monitor output options
• Customized device-driver and application toolkits

µLIA-320 USB Lock-In Frequently Asked Questions

1. What types of input reference signals does the µLIA-320 accept?
2. What is the lowest input reference frequency the µLIA–320 will accept?
3. Does the µLIA-320 support reference output modes?
4. Is the µLIA-320 a single-phase or dual-phase lock-in?
5. Is the µLIA-320 an analog lock-in or a DSP lock-in?
6. What is the minimum time constant available?
7. What is the phase resolution of the µLIA–320?
8. Is there software provided that allows me to integrate the µLIA–320 into my existing application?
9. What is the highest frequency the µLIA–320 can recover?
10. Does the µLIA-320 measure AC current?
11. Is the µLIA–320 a USB bus-powered device?
12. Can I use the µLIA–320 in standalone mode, without a host PC?
13. What is the physical size and weight of the µLIA-320?
14. Does the µLIA–320 come with a display screen?
15. Do you have any drivers/libraries that would allow me to control the µLIA-320 and collect data using a Raspberry Pi (Linux-like) or some other UNIX-based operating system?

1. What types of input reference signals does the µLIA-320 accept?
The reference input accepts logic-level TTL-compatible signals of arbitrary duty cycle. The reference input is opto-isolated from the rest of the instrument.

2. What is the lowest input reference frequency the µLIA–320 will accept?
The µLIA-320 accepts reference frequencies as low as 800 Hz. Many potential customers are interested in the ~1 kHz to 10 kHz frequency range, which the µLIA-320 handles well.

3. Does the µLIA-320 support reference output modes?
Yes. Reference output mode is used in measurement situations where the lock-in amplifier must generate a “master clock” or analog driving signal for the rest of the experimental setup. In this mode, the lock-in is automatically locked to the reference signal it is outputting. For the µLIA-320, an internal relay controls whether the back-panel Reference Input/Output BNC connector is accepting an input or outputting a reference signal. In reference output mode, a jumper internal to the µLIA-320 selects between digital or analog output signals. The digital signal is logic-level TTL-compatible, with 50% duty cycle. The analog signal is bipolar sinusoidal with a fixed Vpeak amplitude. Contact us for your exact application requirements.

4. Is the µLIA-320 a single-phase or dual-phase lock-in?
The µLIA-320 is a dual-phase lock-in amplifier, which means it has two independent analog multiplier channels (X and Y), along with two independent local-oscillator channels that are each fed to one input of these multipliers. The AC-amplified signal is then fed to the other input of the multipliers. For a conventional quadrature recovery scheme, the X and Y local-oscillator channels are always held 90 degrees out of phase from each other. The angle of these XY axes can then be adjusted with respect to the reference input signal. The advantage of a dual-phase lock-in is that it can always recover both the in-phase and quadrature (90 degrees out of phase) components of the signal, giving the vector magnitude (R) and phase angle (θ) with respect to the input reference signal. For many applications, only the magnitude R is required, which a dual-phase lock-in can recover unambiguously.

5. Is the µLIA-320 an analog lock-in or a DSP lock-in?
The µLIA-320 is a modern digitally-controlled mixed-signal approach to an analog sine-wave multiplier lock-in amplifier. This recovery approach is similar to the Stanford Research SR510 & SR530 analog lock-ins. The front-end gain blocks, analog multipliers, and back-end demodulator low-pass filters are pure analog, and are designed to handle the full instrument bandwidth (400 kHz). These analog blocks do the 'heavy lifting' of the instrument, allowing the recovered quasi-DC baseband to be sampled at 1 ksample-pair/sec, digitally low-pass filtered, and (x, y) samples streamed over USB to the host PC.

6. What is the minimum time constant available?
The minimum (“fastest”) time constant is 1 ms, and is determined by the bandwidth of the demodulator analog low-pass anti-aliasing filters. Selecting “0 ms” in uLIA-320 Panel or the uLIA_dd toolkit will return (x, y) samples with this inherent bandwidth only and no additional digital low-pass filtering.

7. What is the phase resolution of the µLIA–320?
The phase resolution or adjustability of the X and Y channels relative to the reference channel is 0.1 degrees. This value is determined by the bit-width of the Direct Digital Synthesis (DDS) phase-tuning registers. The µLIA-320 utilizes DDS’s with 12-bit phase-tuning registers, hence the underlying settability of the reference channel phase is one part in 4096.

8. Is there software provided that allows me to integrate the µLIA–320 into my existing application?
Yes. The uLIA_dd device-driver toolkit (for Visual Studio C/C++) & accompanying standalone .DLL (for LabVIEW, Python, & other languages that can call into an external module) provides an API for the host/µLIA-320 message protocol for users that desire to tie the lock-in functionality into their own software. Source code & technical support for the uLIA_dd toolkit are included with the µLIA-320.

9. What is the highest frequency the µLIA–320 can recover?
The µLIA-320 can recover signals up to 400 kHz.

10. Does the µLIA-320 measure AC current?
Not directly. The µLIA-320 accepts bipolar voltage inputs in the ±10V range on the front-panel Signal Input BNC. This input is AC-coupled to a low-noise JFET input amplifier. Current inputs must first be converted to the voltage domain by an appropriate transimpedance amplifier for the sensor.

11. Is the µLIA–320 a USB bus-powered device?
No. The µLIA-320 has its own separate international power supply and thus draws negligible power from the USB bus.

12. Can I use the µLIA–320 in standalone mode, without a host PC?
Yes. The front-panel Monitor Output BNC outputs one of four internal analog signals. The µLIA-320 must first be configured by the host while attached to USB, and the X or Y DC output selected by software as the Monitor Output. When the µLIA-320 is detached from USB, the lock-in will hold its last-set configuration, and the selected X or Y signal will continue to appear on Monitor Output.

13. What is the physical size and weight of the µLIA-320?
The µLIA-320 consists of a single module of dimensions 5.6 in W x 7.2 in L x 1.7 in H (14.1 cm W x 18.3 cm L x 4.3 cm H) and weight 1.4 lbs (0.6 kg). The supplied standalone international power supply has dimensions 3.0 in W x 5.8 in L x 1.7 in H (7.6 cm W x 14.7 cm L x 4.3 cm H). The power supply attaches to the µLIA-320 module by a DIN-5 male plug on a 48 in L (122 cm L) cord. The µLIA-320 module and power supply together weigh 2.9 lbs (1.3 kg).

14. Does the µLIA–320 come with a display screen?
The µLIA-320 has a ‘virtual’ display screen through the uLIA-320 Panel program, on your desktop PC or laptop. This virtual front-panel is far more versatile and economical than any dedicated display screen we could provide.

15. Do you have any drivers/libraries that would allow me to control the µLIA-320 and collect data using a Raspberry Pi (Linux-like) or some other UNIX-based operating system?
Not directly. The µLIA-320 will work on other operating systems, as it is USB 2.0 compatible, which is a platform-independent standard. However, the underlying host-side USB stack we supply is WinUSB-based, which is specific to MS Windows. The µLIA-320 ships with the uLIA_dd device-driver toolkit, which handles the details of the host/lock-in message protocol. This toolkit calls into the WinUSB & Registry interface module uLIAUsb.dll. Source code (standard C) is provided for the uLIA_dd toolkit, but not for the underlying .DLL. For a different operating environment than Windows (e.g. Raspberry Pi), there are a small number of USB API calls that would have to be implemented in order to port the uLIA_dd toolkit. Contact us for further details.