How a MEMS Sensor Uses a Reference to Improve Z-Axis Accuracy
This patent describes a tiny sensor that measures up-and-down motion more accurately by including a special surrounding structure that helps cancel out environmental interference.
Original patent title: “MEMS sensor with movable z-axis sensing element”
This patent describes a tiny sensor that measures up-and-down motion more accurately by including a special surrounding structure that helps cancel out environmental interference. Granted to Analog Devices in 2012 with 21 claims and 22 forward citations, and it is expected to expire in 2028.
Coverage
What does this patent actually cover?
This MEMS (Micro-Electro-Mechanical System) sensor improves accuracy by using a dedicated reference structure. The sensor includes a main MEMS structure with a part that can move, called a movable mass, all built on a substrate. Crucially, a separate reference structure is placed radially outward from the main MEMS structure and is electrically connected to the movable mass (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1). This setup allows the sensor to measure changes in capacitance between the movable part and an electrode on the substrate (Claim 16). By comparing or offsetting measurements using the reference structure, the sensor can become more accurate, especially for detecting motion along the z-axis (up and down). For example, if temperature changes affect the entire chip, the reference structure helps the sensor distinguish actual motion from environmental noise.
The gap
What does this patent NOT cover?
- Does not cover MEMS sensors that do not include a separate reference structure.
- Does not cover reference structures that are not positioned radially outward from the main MEMS structure.
- Does not cover reference structures that are not electrically connected to the movable mass of the MEMS structure.
- Does not cover MEMS sensors that measure motion using methods other than changes in capacitance.
- Does not cover MEMS sensors primarily designed for motion sensing along the x or y axes, as the claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more → focus on z-axis measurement.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The clever part is integrating a dedicated reference structure that is both radially outward from the main sensor and electrically connected to its movable part. This specific arrangement allows the sensor to effectively compensate for environmental changes, ensuring that the measured signal truly reflects motion rather than external noise.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Smartphone accelerometers
Automotive airbag sensors
Industrial vibration monitors
Wearable fitness trackers
Drone flight controllers
Why it matters
The bigger picture
Accurate MEMS sensors are vital for many modern devices, from smartphones to industrial equipment. This patent addresses a fundamental challenge: how to make these tiny sensors more reliable by reducing errors caused by environmental factors like temperature changes. By improving measurement accuracy, this technology allows for more precise control and data collection in a wide range of applications, which is critical for performance and safety.
Filed
September 5, 2008
Granted
April 3, 2012
Market context
Who's building on this
Companies in this space
Analog Devices Inc., the original assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →, remains a leading developer and manufacturer of high-performance MEMS sensors. Other major semiconductor companies like STMicroelectronics, Bosch Sensortec, and NXP Semiconductors also continuously innovate in the MEMS space, often building on foundational concepts like environmental compensation to create more robust and accurate sensors for various applications.
Market impact
The development of more accurate MEMS sensors, like the one described here, has enabled their widespread adoption in critical applications where reliability is paramount. This patent contributes to the ongoing effort to make MEMS technology more robust, expanding its use from consumer gadgets to high-reliability industrial and automotive systems. Improved accuracy reduces false readings and enhances the performance of products relying on motion sensing.
Claim 1 — Plain English
What this patent covers
This MEMS (Micro-Electro-Mechanical System) sensor improves accuracy by using a dedicated reference structure. The sensor includes a main MEMS structure with a part that can move, called a movable mass, all built on a substrate. Crucially, a separate reference structure is placed radially outward from the main MEMS structure and is electrically connected to the movable mass (Claim 1). This setup allows the sensor to measure changes in capacitance between the movable part and an electrode on the substrate (Claim 16). By comparing or offsetting measurements using the reference structure, the sensor can become more accurate, especially for detecting motion along the z-axis (up and down). For example, if temperature changes affect the entire chip, the reference structure helps the sensor distinguish actual motion from environmental noise.
The clever bit
The clever part is integrating a dedicated reference structure that is both radially outward from the main sensor and electrically connected to its movable part. This specific arrangement allows the sensor to effectively compensate for environmental changes, ensuring that the measured signal truly reflects motion rather than external noise.
What it does not cover
- Does not cover MEMS sensors that do not include a separate reference structure.
- Does not cover reference structures that are not positioned radially outward from the main MEMS structure.
- Does not cover reference structures that are not electrically connected to the movable mass of the MEMS structure.
- Does not cover MEMS sensors that measure motion using methods other than changes in capacitance.
- Does not cover MEMS sensors primarily designed for motion sensing along the x or y axes, as the claims focus on z-axis measurement.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
PatentBrief Score
Impact Score
Moderate
Citation count
27/40
Moderately cited
Claim breadth
14/20
Broad claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
5/20
Granted 10–20 years ago
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$59K – $187K
Midpoint $117K · 1.9 yr remaining · industry ×1.5
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Claim text not yet imported for this patent
The original legal language
Original claims
21 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Judy, M. W., & Zhang, X. (2012). How a MEMS Sensor Uses a Reference to Improve Z-Axis Accuracy (U.S. Patent No. 8,146,425). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/8146425/mems-sensor-with-movable-z-axis-sensing-element
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How a MEMS Sensor Uses a Reference to Improve Z-Axis Accuracy cover?
This patent describes a tiny sensor that measures up-and-down motion more accurately by including a special surrounding structure that helps cancel out environmental interference.
Who owns patent US 8146425?
Analog Devices owns this patent, granted in 2012.
When does this patent expire?
This patent is expected to expire on September 5, 2028, when the invention enters the public domain.
What is patent US 8146425 cited by?
This patent has been cited by 22 later patents that build on its ideas.
What problem does this patent solve?
Accurate MEMS sensors are vital for many modern devices, from smartphones to industrial equipment. This patent addresses a fundamental challenge: how to make these tiny sensors more reliable by reducing errors caused by environmental factors like temperature changes. By improving measurement accuracy, this technology allows for more precise control and data collection in a wide range of applications, which is critical for performance and safety.
What does this patent NOT cover?
Does not cover MEMS sensors that do not include a separate reference structure.
Same assignee
More from Analog Devices
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