All Sensors Corp Inc v. Honeywell Data Instruments

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: All Sensors Corporation, Inc. (California) and Sensortechnics GmbH (Germany)
  • Defendant: Honeywell Data Instruments, Inc. (Delaware)
  • Plaintiff’s Counsel: Coudert Brothers
• Case Identification: 5:01-cv-20678, N.D. Cal., 07/26/2001
• Venue Allegations: Venue is asserted based on a substantial portion of the alleged activities being conducted or having a substantial impact in the Northern District of California.
• Core Dispute: Plaintiffs seek a declaratory judgment that their pressure sensor products do not infringe Defendant’s patent related to error-compensating pressure transducers, and that the patent-in-suit is invalid.
• Technical Context: The technology concerns silicon-based pressure sensors, used in medical and industrial applications, and methods for improving their accuracy by compensating for measurement errors caused by temperature and other factors.
• Key Procedural History: This is a declaratory judgment action, filed after the Defendant, Honeywell, allegedly accused Plaintiffs of infringing the patent-in-suit and demanded they cease and desist from manufacturing and selling the accused products. The complaint alleges that during patent prosecution, the patentee made specific representations to the U.S. Patent and Trademark Office that narrowed the scope of key claim terms.

Case Timeline

Date	Event
1996-07-10	'978 Patent Priority Date
1999-01-01	Approximate launch of Plaintiffs' product activities
1999-12-01	Approximate date of distribution agreement between Plaintiffs
2000-02-15	U.S. Patent No. 6,023,978 Issues
2001-07-26	Complaint for Declaratory Judgment Filed

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 6,023,978 - Pressure Transducer With Error Compensation From Cross-Coupling Outputs Of Two Sensors

• Issued: February 15, 2000

The Invention Explained

• Problem Addressed: The patent's background describes that pressure transducers, particularly those using silicon strain gauges, are sensitive to environmental factors like temperature, which can introduce errors into pressure readings. Conventional methods for compensating for these errors were described as "costly and time-consuming," often requiring extensive characterization and adjustment for each individual sensor ('978 Patent, col. 1:17-45; col. 2:13-15). Prior art approaches also required pairing sensors with opposite error characteristics, which necessitated a pre-characterization step ('978 Patent, col. 2:31-43).
• The Patented Solution: The invention proposes a pressure transducer that uses at least two sensors with "substantially similar or substantially identical error characteristics" ('978 Patent, Abstract). Instead of pairing opposite-error sensors, this approach pairs similar-error sensors and electrically "cross-couples" their outputs. This arrangement is designed to cause the similar error signals from each sensor to cancel each other out, leaving a signal that represents the actual pressure measurement ('978 Patent, col. 2:57-65). The specification suggests this is best achieved by selecting sensors formed in close proximity on the same silicon wafer, as their process-related errors will tend to be very similar, thus avoiding the need for costly individual characterization ('978 Patent, col. 4:10-28).
• Technical Importance: This approach aimed to provide a lower-cost method for producing accurate pressure transducers by eliminating the need for extensive, individualized error characterization and matching ('978 Patent, col. 10:52-58).

Key Claims at a Glance

• The complaint alleges that every claim of the patent contains the key limitation regarding sensor characteristics (Compl. ¶13). Independent Claim 1 is representative:
  • A pressure transducer comprising: a first sensor; and a second sensor;
  • the first and second sensors having substantially similar error characteristics,
  • each of the first and second sensors being arranged to be subjected to at least one of a first pressure and a second pressure and to provide an output indicative of the pressure exerted thereon,
  • the outputs of the sensors being electrically cross-coupled to each other so that an error in the first sensor is compensated with a substantially similar error in the second sensor.
• The complaint does not specify any dependent claims.

III. The Accused Instrumentality

Product Identification

• The "Disputed Product Design," which includes the Millivolt Output Low Pressure Sensor ("ADCXL Sensor") and the Amplified Output Low Pressure Sensor ("ADCAL Sensor") (Compl. ¶9).

Functionality and Market Context

• The accused products are described as low-pressure sensors for medical and industrial applications (Compl. ¶10). They are comprised of two integrated circuit sensors (chips) made from semiconductor material, arranged to measure pressure with high accuracy and reduced error from temperature and other factors (Compl. ¶9).
• A central allegation in the complaint is that, unlike the preferred embodiment of the '978 Patent, "All Sensors does not use chips from the same wafer to create the two sensors included as part of the Disputed Product Design" (Compl. ¶10).

IV. Analysis of Infringement Allegations

No probative visual evidence provided in complaint.

The complaint seeks a declaratory judgment of non-infringement. The table below summarizes the Plaintiffs' core non-infringement position as alleged in the complaint.

'978 Patent Infringement Allegations

Claim Element (from Independent Claim 1)	Alleged Non-Infringing Functionality	Complaint Citation	Patent Citation
the first and second sensors having substantially similar error characteristics...	Plaintiffs' products are comprised of two sensor chips, but Plaintiffs allege they do not use chips from the same wafer and thus do not rely on the chips being "substantially similar" or "substantially identical" as those terms were allegedly defined by the patentee during prosecution.	¶9, ¶10, ¶13	col. 11:40-42
the outputs of the sensors being electrically cross-coupled to each other so that an error in the first sensor is compensated with a substantially similar error in the second sensor.	By asserting that their sensors do not have "substantially similar" characteristics as required by the preceding limitation, Plaintiffs implicitly deny that their products can achieve the claimed compensation via cross-coupling as recited.	¶18	col. 11:46-49

Identified Points of Contention

• Scope Questions: The central dispute concerns the proper construction of the claim term "substantially similar error characteristics." Does this term, as used in the patent, require the two sensors to be sourced from the same silicon wafer, or even be adjacent on that wafer, as Plaintiffs allege the patentee represented to the PTO? (Compl. ¶13). This raises a question of potential prosecution history disclaimer.
• Technical Questions: A key factual question is whether Plaintiffs' sensors—even if constructed from chips from different wafers—do, in fact, exhibit "substantially similar error characteristics." This would require technical evidence and expert testimony to resolve, regardless of how the term is ultimately construed.

V. Key Claim Terms for Construction

• The Term: "substantially similar error characteristics"
• Context and Importance: This term is the lynchpin of the infringement dispute. Plaintiffs’ non-infringement case hinges on a narrow construction of this term, allegedly based on the patent's prosecution history (Compl. ¶13). Its definition will determine whether the patent covers only devices using sensors from a single wafer or has a broader reach.
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The plain language of Claim 1 does not contain any limitation requiring the sensors to be from the same wafer ('978 Patent, col. 11:40-49). The specification states that the invention "may theoretically be accomplished with any type of sensor," before stating a preference for silicon sensors from the same wafer, which may suggest that the wafer-based method is a preferred embodiment, not a limiting feature of the entire invention ('978 Patent, col. 4:5-9).
  • Evidence for a Narrower Interpretation: The specification repeatedly and strongly emphasizes that the inventive concept is best realized by using sensors from the same silicon wafer, especially adjacent dies, to ensure their characteristics are nearly identical ('978 Patent, col. 4:15-28). The Abstract also highlights using "substantially identical silicon sensors formed in close proximity on the same wafer." Plaintiffs allege that the patentee explicitly limited the term during prosecution to refer to chips from the same wafer, which if proven would create a prosecution history disclaimer that could override the broader claim language (Compl. ¶13).

VI. Other Allegations

• Invalidity: The complaint includes a claim for a declaratory judgment of patent invalidity, alleging the '978 Patent fails to meet the conditions of 35 U.S.C. §§ 101, 102, 103, and/or 112 (Compl. ¶42). The complaint specifically identifies U.S. Patent No. 4,565,097 as prior art that allegedly taught the "use or selection of chips for use in a sensing device from different wafers, yet having 'substantially the same' error characteristics" before the '978 invention was made (Compl. ¶14).
• Related Claims: The complaint also brings claims for defamation, false marking, and unfair competition against Honeywell. These are based on allegations that Honeywell falsely told customers that Plaintiffs were infringing the '978 Patent and that Honeywell falsely marked its own "DUXL" product with the '978 Patent number (Compl. ¶22, ¶29-32). The request for an "exceptional case" finding is for the purpose of seeking attorneys' fees (Compl. ¶20).

VII. Analyst’s Conclusion: Key Questions for the Case

• A core issue will be one of claim construction and estoppel: Is the scope of the term "substantially similar error characteristics" limited by representations made during prosecution to the PTO? The resolution of this question, which centers on whether the patentee disclaimed broader coverage, will likely be dispositive for the non-infringement analysis.
• A central evidentiary question will be one of invalidity: Can Plaintiffs prove by clear and convincing evidence that the asserted claims are anticipated or rendered obvious by prior art, such as the cited '097 patent, which allegedly discloses using sensors from different wafers that have similar error profiles?
• A key factual question for infringement will be technical characterization: Irrespective of the claim construction outcome, do the sensor chips in Plaintiffs' accused products, which are allegedly sourced from different wafers, in fact possess "substantially similar error characteristics" sufficient to meet the claim limitation? This would require a technical deep-dive and a battle of experts.