Thermal Mass & Variable Area Meter Patents: Leaders vs Long Tail 2026
- 51.3% concentration. The top 5 assignees hold 162 of 316 records in scope, with one leader alone accounting for 72 — a field where the top of the table is tight and the rest thins out fast.
- Filings down 46% since 2021. From 13 filings in 2021 to 7 in 2024 (the last complete year), the pace of new activity has cooled well before publication lag makes 2025-26 numbers reliable.
- G01F is a minority class. Only 13.9% of records sit in G01F (flow measuring) itself — most of the corpus arrives from adjacent classes like material analysis (G01N) and separation processes (B01D), meaning core meter claims sit alongside process and biomedical filings.
Filing growth compares 2021 (13 records) with 2024 (7) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 316 records in scope (CR5), not by the ranked leaders only.
What this landscape covers
This dataset tracks patent families addressing thermal mass flow meters, variable area flowmeters and rotameters where the claims engage practical measurement problems: gas composition dependence, calibration gas requirements, low flow sensitivity, condensation risk, float material selection, and viscosity effects. It spans publications from 2015 through the 2026 cut-off, covering 316 records in total.
The search string pairs the meter type with the operating condition that makes it hard to engineer, which is why the technology composition below spreads across process and biomedical classes as well as G01F itself — many of these meters are claimed inside a specific application, not as standalone instruments.
Filing trend and technology composition
Two views of the same 316-record corpus: how filing activity has moved year over year, and which IPC subclasses carry the claims.
Filing trend: a cooling field
Filings peaked at 16 in 2018 and have since drifted down; the 2021-to-2024 span shows a 46% decline (13 to 7), the most recent period the data can support without publication-lag distortion. Treat 2025 and 2026 figures as still filling in rather than as evidence of a further slowdown.
Where the claims sit
G01N (material analysis, 32.3%) and A61F (implants and prostheses, 25.3%) outweigh G01F (flow measuring proper, 13.9%), which tells you a large share of this corpus is meters embedded in medical or analytical apparatus rather than filed as general-purpose flow instruments. B01D (separation, 13.3%) and A61M (body fluid devices, 11.1%) point to the same pattern in industrial gas handling and clinical delivery contexts.
Shares are the percentage of the 316 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Thermal Mass and Variable Area Meters with Eureka
This page is one run against one query. Ask Eureka your own question about thermal mass and variable area meters and every answer comes back with the patent numbers behind it.
Try EurekaMost-cited and representative filings
US10514289B2 — Mass flow rate measurement method and thermal mass flow meter/controller
A capillary heating thermal mass flow meter that detects fluid temperature and pressure and corrects the measured mass flow rate using pre-acquired change rates for temperature and pressure. The correction lets the meter hold accuracy even as the fluid's temperature or pressure shifts during measurement, without added hardware complexity.Filed by Proterial, Ltd. (formerly Hitachi Metals), published 2019-12-24.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US5944048A | Method and apparatus for detecting and controlling mass flow | 195 |
| 2 | US4656865A | System for analyzing permeation of a gas or vapor through a film or membrane | 172 |
| 3 | US6217890B1 | Absorbent article which maintains or improves skin health | 171 |
| 4 | US5975126A | Method and apparatus for detecting and controlling mass flow | 155 |
| 5 | US6610263B2 | System and process for removal of pollutants from a gas stream | 153 |
| 6 | US6152906A | Absorbent article having improved breathability | 120 |
| 7 | US20040109800A1 | System and process for removal of pollutants from a gas stream | 106 |
| 8 | US6296862B1 | Absorbent article which maintains or improves skin health | 104 |
| 9 | US6579507B2 | System and process for removal of pollutants from a gas stream | 103 |
| 10 | US4112737A | Transformer fault detection | 102 |
Citation counts reflect influence inside the searched corpus and skew toward older filings; they are not a measure of current commercial relevance.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Three read-outs from the concentration, trend and classification figures above.
The top of the table is settled, the rest is open
With the top 5 assignees holding 51.3% of all 316 records and the leader alone at 72, a new entrant is not fighting a crowded field of equals — it is filing around one or two dominant portfolios plus a long tail of single- or few-filing entrants below tenth place (6 records).
Activity has cooled from its 2018 peak
The peak year was 2018 at 16 filings; by the last fully-lagged year, 2024, filings had fallen to 7 from 13 in 2021. That is a real decline over a three-year window that avoids the unreliable 2025-26 tail, not a comment on the technology's maturity.
Most claims arrive via an application, not the meter itself
G01N and A61F together outweigh G01F by a wide margin, meaning the practical calibration and material problems this search targets are mostly being solved inside medical devices, absorbent products and gas separation systems — filing a standalone meter claim may face less direct prior art than filing inside those application classes.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to thermal mass and variable area meters, with the prior art for and against each one.
Who is active, and where the gate sits
A small set of assignees hold most of the volume; recent-year momentum among the named entities in this evidence set has largely gone flat.
One assignee sets the floor
The leading assignee holds 72 of the 316 records in scope — roughly 23% on its own before the rest of the top 5 is even counted. Any freedom-to-operate review in this space starts here.
A wide base below the leaders
The ranking runs to 100 assignees total, and the drop from fifth (8 records) to tenth (6 records) is shallow — most of the field below the top 10 is filing in small numbers, which is typical of a mature, application-driven niche rather than a single race to dominance.
Collaboration is narrow and repeated
Ten co-assignee pairs appear in the data, with the strongest trio of inventor-linked pairings each recurring at 6 shared records — a sign of a small internal team filing together repeatedly rather than broad industry collaboration.
| Assignee | Recent year | YoY |
|---|---|---|
| Kimberly-Clark Worldwide, Inc. | 0 | — |
| Third Pole, Inc. | 0 | — |
| EnviroScrub Technologies Corp. | 0 | — |
| LOCI CONTROLS INC | 0 | -100% |
| Midwest Research Institute | 0 | — |
| FISCHER & PORTER CO | 0 | — |
| Praxair Technology, Inc. | 0 | — |
| Procter & Gamble Co. | 0 | — |
Where to take this
The dataset points to a concentrated leadership position and a cooling but still-active filing base. Two directions follow from that.
Map freedom-to-operate around the leader's 72 records
Before filing a new thermal mass or variable area meter claim, a claim-by-claim review of the leading assignee's portfolio is the highest-value first step, given it accounts for nearly a quarter of the entire corpus.
Explore assignee portfolios in EurekaTest white space in under-claimed sub-areas
Condensation-resistant coatings, multi-gas calibration algorithms and float material substitution show thinner direct coverage than the dense G01N/A61F classes — worth a targeted novelty search before committing engineering resources.
Run a white space search in EurekaCommon questions
This dataset shows a single assignee leading with 72 of the 316 records in scope, well ahead of the rest of the field. The top 5 assignees combined hold 162 records, or 51.3% of the total, so filing decisions in this space should start with a review of that leader's claims rather than treating the field as evenly distributed. Below the top 10, which together hold 62.3% of all records, the ranking spreads thinly across 100 companies.
Filings peaked in 2018 at 16 in a single year and have since declined; comparing the last two complete years available, 2021 (13 filings) to 2024 (7 filings), shows a 46% drop. Data from 2025 and 2026 is still incomplete because publication typically lags filing by around 18 months, so those years should not yet be read as confirming or reversing that trend. On the evidence available, the field has cooled from its 2018 high point rather than accelerated.
The largest classes in this corpus are G01N (material analysis and testing, 32.3% of records) and A61F (implants and prostheses, 25.3%), both ahead of G01F (flow, level and volume measuring, 13.9%), the class most directly associated with meters themselves. This reflects how many of these patents claim a meter as part of a medical device, gas separation system, or analytical instrument rather than as a freestanding flow meter. B01D (separation processes) and A61M (body fluid devices) also carry meaningful shares, pointing to industrial gas and clinical delivery applications.
US10514289B2 covers a capillary heating thermal mass flow meter that corrects its output using pre-acquired change rates of mass flow with respect to temperature and pressure, measured by an onboard sensor. The mechanism is specific to that correction approach, so it primarily constrains designs that use the same temperature-and-pressure change-rate correction method inside a capillary-type sensor, rather than thermal mass flow measurement generally. Designs using different correction inputs, different sensor geometries, or non-capillary heating approaches sit outside its most direct claim scope, though a full freedom-to-operate check should compare claim language line by line.
Relative to the dense G01N and A61F classes, this corpus shows thinner direct coverage in areas like condensation-resistant sensor coatings, multi-gas calibration algorithms, and float material substitution for variable area meters. These sit adjacent to well-covered ground rather than in an unclaimed vacuum, so a new filing there should still expect to design around the leading assignee's core patents. Low-flow float geometry and viscosity-compensated capillary sensing are worth checking specifically, since neither dominates the classification data the way G01N-driven material analysis claims do.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.