Net-phase flow NMR for compact applications

[Display omitted] •A compact low-cost flowmeter capable of working in a low field, gap-magnet-based solution, enables non-invasive industrial flow sensors.•A PCB-based second-order shim set was developed to target the desired flow-VOI.•The proposed solution remains compatible with all other NMR techniques.•The near-2D flow profile leads to a significantly higher SNR compared to round tubing. The net phase of the NMR signal is proposed as a robust mechanism for the encoding of fluid flow velocity into phase, showing local bijectivity. While magnitude-based or imaging-based methods suffer from loss of signal, by increasing the flow rate, the present method enables us to maintain the high SNR even for the case of fast flow. In addition, it is shown that a well-engineered flow channel is also necessary, which is not the case for traditional cylindrical flow channels. In this contribution, we report on implementing this approach in a low-cost NMR-based flowmeter for use in a low field (1 T) setting, for example, for monitoring reaction flow industrial processes.