Work

Characterizing timing parameters in commercial SERF-OPM multichannel systems for biomagnetic field sensing

Year: 2025

Type: article

Abstract: Spin-Exchange Relaxation-Free Optically Pumped Magnetometers (SERF-OPMs) are increasingly used in multichannel biomagnetic sensing, yet their timing performance remains poorly characterized. This contribution presents the first cross-platform study of time delay, group delay, intra-channel variability, and settling time across four commercial SERF-OPM systems: Neuro-1 and QZFM Gen.2 (QuSpin Inc.), and HEDscan and FLv2 (FieldLine Inc.). Measurements were performed inside a magnetically shielded room (BMSR-2.1, PTB, Berlin) using a previously introduced test bench. Results show frequency-dependent delays of 1–10 ms, intra-channel spreads up to ± 1 ms, group delays between 1–15 ms, and settling times of 2–55 ms. Clear differences in manufacturer design strategies were observed: QuSpin minimizes intra-channel variability through digital delay equalization, whereas FieldLine employs per-sensor calibration to optimize bandwidth and phase matching. In all systems, the time delay deviation between channels is in the sub-millisecond range in the 20–140 Hz band, sufficient for magnetoencephalography source localization. However, longer settling times in some platforms limit performance for rapid stimulation protocols. These findings provide the first vendor-comprehensive benchmarks for timing parameters in commercial SERF-OPM systems. They highlight the trade-offs between bandwidth, delay, and calibration strategies, and underscore the need for rigorous timing characterization to ensure waveform fidelity. The results are directly relevant to applications such as stimulation-evoked responses, brain–computer interfaces, and closed-loop neuromodulation.

Source: Measurement

DOI: 10.1016/j.measurement.2025.120140