> For the complete documentation index, see [llms.txt](https://docs.anthriq.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.anthriq.com/xbud/faq.md). # FAQ ## About the product ### What is xBud? xBud is a multimodal analog front-end for biosignal acquisition. It amplifies and filters EEG, ECG, EMG, and EOG from dry electrodes, then hands conditioned analog voltages to a data-acquisition device (DAQ) that digitises them. BXI Studio drives the acquisition. It is built for teaching labs, coursework, and prototyping. ### What does xBud do that a generic DAQ does not? A DAQ digitises voltages in the volt range. Biopotentials arrive at the skin in microvolts, buried in mains interference. xBud is the stage between: instrumentation amplification, band-limiting, and active common-mode rejection through a driven-right-leg circuit. Without it a DAQ records noise. ### Which channel variants exist? Four, eight, twelve, and sixteen EXG channels, each with dedicated REF, AGND, and DRL. Order any or all of the four subject interfaces with any variant: EEG cap, EEG headband, EMG armband, and ECG chest-strap. ### Which signals can xBud record? EEG, ECG, EMG, and EOG, through one front-end. The fixed 100× gain and 0.5–300 Hz passband cover these ranges without reconfiguration. ## Safety and compliance ### Can xBud be used on human subjects? xBud is a research and education device. It is not a medical device and is not approved for clinical, diagnostic, or therapeutic use. Operate it under the supervision of trained personnel in a teaching or research setting. ### Is xBud electrically isolated? Yes. xBud has a 3 kV isolation barrier in its power supply, and the supplied 2-pin adapter is double-insulated, so it further separates xBud's DC supply from the mains line and lets the low-voltage side float. The design is tested for laboratory use. It is still not a certified medical device. Certification to IEC 60601-1 covers the whole system, including patient leakage current, creepage and clearance, behaviour under fault conditions, and documented testing, rather than the barrier voltage alone, and xBud is not characterised for patient leakage current. The practical consequence: keep the subject clear of other mains-powered equipment while they are connected, such as a laptop charger or a desktop PC. Each additional mains-referenced path through the subject adds a fault route that xBud's own barrier does not cover. Running the host laptop on battery also removes the most common source of mains hum. See [Power & Safety](/xbud/technical-guide.md#power-and-safety). ### Where are the certifications and warranty terms? For certifications, compliance declarations, and warranty terms, contact . ## Hardware and performance ### Can the gain or the filters be changed? No. Gain is fixed at 100× and the low-pass at 300 Hz, with 0.5 Hz AC coupling. There are no switches to set and nothing to configure in software. Change the recorded bandwidth by filtering in BXI Studio, which affects the view rather than the front-end. ### Does the 300 Hz low-pass limit surface EMG? It bounds it. Surface EMG is often quoted as 20–450 Hz, so the band above 300 Hz is not recorded. In practice that content carries poor signal-to-noise at the skin, and the power that drives amplitude, burst detection, and the usual time-domain features sits well below 300 Hz. EMG recordings for teaching and gesture work are unaffected. ### What is the input-referred noise? xBud has a noise floor of < 10 µV (0.5 - 45 Hz). See [Specifications](/xbud/specifications.md). ### Which DAQ does xBud need? xBud is DAQ-agnostic. It currently ships tested with NI USB-600x, NI mioDAQ (USB-6451), and NI cDAQ, all supported in BXI Studio. Resolution, input range, and sampling rate are properties of the DAQ, not of xBud: see [Specifications](/xbud/specifications.md). ### What sampling rate can I record at? The DAQ decides. As a guide: about 1.2 kHz per channel across four channels on a USB-6008, 4–5 kHz per channel on the mioDAQ, and up to 10 kHz per channel on a cDAQ. On multiplexing DAQs the maximum is shared across the channels in the task, so the rate per channel falls as you add channels. EXG signal sampling rates of around 2 kS/s are more than sufficient. This is supported by the LPF cutoff being fixed at 300 Hz, providing ample temporal resolution. See [Specifications](/xbud/specifications.md). ### Wet or dry electrodes? Dry Ag/AgCl coated electrodes, with comb contacts for hair and disc contacts for bare skin. Contact pressure replaces conductive gel, so seat each electrode firmly and evenly. Gelling the AGND and DRL contacts is worthwhile. Neither carries a recorded signal, so gel there lowers the common-mode path impedance and reduces mains hum without affecting the dry recording sites. ## Software and data ### How are experiment events marked? Two ways. A two-button marker box cables to the xBud chassis and drives two digital marker lines into the DAQ; each press records a marker time-aligned with the signal. BXI Studio also records software markers from a keypress. BXI supports both event-type and epoch-type markers, and arbitrary labels can be assigned. ### Can I record without BXI Studio? Yes. The NI-DAQmx Python and C/C++ APIs address the DAQ directly. Divide each reading by the fixed 100× gain to recover electrode volts. See [SDK & Dev Resources](/xbud/technical-guide.md#read-the-daq-programmatically). ### What format is the exported data? CSV, carrying the channel names you set and the marker columns. Any analysis tool reads it: Python, MATLAB, R, or a spreadsheet. See [Exporting a dataset](/bxi-studio/streams/exporting-a-dataset.md). ### Which operating systems are supported? xBud depends on BXI Studio and the NI-DAQmx driver rather than imposing its own requirement. Check the supported versions in the BXI Studio requirements and the NI-DAQmx documentation. ## Teaching use ### Why is nothing visible on the EEG trace? Usually because EEG rhythms are not visible by eye. A 10 µV alpha rhythm sits inside a trace that also carries drift and blinks. Open the **Fast Fourier Transform** instead and compare two conditions, such as eyes open against eyes closed. See [Choose a visualization](/xbud/technical-guide.md#choose-a-visualization). ### What can students measure in one lab session? The eyes-closed alpha rhythm is the usual first result: two 30-second recordings, with the effect visible in the spectrum within seconds. See [Record eyes-closed alpha](/xbud/experiments/eyes-closed-alpha.md). ECG and EMG bursts are visible directly in the time domain and need less setup.