The dataset ranks 31 assignees, with the leading company holding 25 of the 143 records in scope – more than double the fifth-place holder’s 10. The top 5 assignees together hold 81 records, or 56.6% of all records in scope, meaning over half the documented claim space sits with a small number of long-established flow-instrumentation manufacturers. Below the top 10, which together hold 79.0% of records, the field thins into a long tail of single- or few-filing entrants.

Filings peaked at 10 in 2021 and fell to 3 by 2024, a 70% decline over that three-year span, which points to a cooling rather than a growing field for the current assignee set. That said, publication typically lags filing by around 18 months, so 2025 and 2026 figures in any dataset are necessarily incomplete and should not be read as continued decline. The safest reading is that the field peaked around 2021 and has since returned to a lower, steadier filing rate.

The search scope centres on reliability and accuracy issues rather than the core measurement principle: liner material selection, electrode fouling, behaviour near the fluid’s conductivity limit, empty pipe detection, grounding requirements, and pulsed excitation schemes. Almost all records – 91.6% of the 143 in scope – sit under IPC class G01F, the flow, level and volume measuring class, confirming this is a mature measurement field where the remaining innovation is in engineering robustness rather than a new sensing approach.