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Drafting a strong patent specification requires navigating a familiar set of competing concerns. The disclosure must be detailed enough to satisfy the statutory requirement that the invention be described in a manner that enables a person of ordinary skill in the art to make and use it, while still preserving flexibility in claim scope. Too little detail invites enablement, possession, or indefiniteness challenges; too much detail can unnecessarily cabin the invention or hand examiners and potential infringers unintended hooks for narrowing interpretation. The balance can be hard to strike when the invention operates using parameters that, in practice, are selected or adjusted through calibration.

That tension frequently surfaces in the question of numerical disclosure. When an invention relies on values that are empirically determined, environment-dependent, or tuned during operation, applicants naturally ask whether the specification must spell out specific numbers. U.S. patent law does not impose a categorical requirement to do so. The touchstone remains whether the disclosure provides sufficient guidance for a person of ordinary skill in the art to determine appropriate values without undue experimentation. Problems arise, however, when examiners treat the absence of numerical values not as a question of breadth or enablement, but as a basis for asserting indefiniteness—particularly in method and device claims that incorporate calibration constants or coefficients.

A recent PTAB decision illustrates how this issue plays out in real-world prosecution, and how mischaracterizing calibration as indefiniteness can lead to improper rejections.

In Ex parte Kawamoto et al., Appeal No. 2025-002549, the claims were directed to a gas concentration measuring device that computed a gas concentration using a defined equation incorporating constants identified as “A” and “β.” The examiner rejected the claims under § 112(b), asserting that the claims were indefinite because the specification did not provide numerical values for those constants.

Claim 1:

1. A gas concentration measuring device, comprising:
   a gas sensor configured to measure a concentration CNOX of specific gas contained in measured gas;
   an oxygen concentration measuring unit configured to measure a concentration CO2 of oxygen in the measured gas;
   and
   a computation unit configured to compute the concentration CNOX of the specific gas, wherein the gas sensor includes:
   a measured gas chamber into which the measured gas is to be introduced,
   a reference gas chamber into which reference gas is to be introduced,
   a diffusion resistance unit configured to regulate a flow velocity of the measured gas to be introduced into the measured gas chamber,
   a pump cell configured to move oxygen from the measured gas chamber into the reference gas chamber, and
   a sensor cell configured to cause a sensor current I to flow therethrough correspondingly to the concentration CNOX of the specific gas in the measured gas chamber, wherein the computation unit is configured to compute the concentration CNOX of the specific gas by using a measured
   value of the concentration CO2 of oxygen with the oxygen concentration measuring unit and a measured value of the sensor current I, the gas concentration measuring device is configured for mounting on a vehicle, the gas sensor is configured to be operatively coupled to an exhaust pipe, the gas sensor is configured to measure the concentration CNOX contained in
   exhaust gas emitted from the exhaust pipe, and the computed concentration CNOX of the specific gas is used in association with the gas sensor, an area of the diffusion resistance unit on a plane orthogonal to an introduction direction of the measured gas is S, a length of the diffusion resistance unit in the introduction direction is L, pressure of the measured gas outside the gas sensor is P, temperature of the diffusion resistance unit is T, a diffusion coefficient of the measured gas is D, and A and β are constants, wherein the computation unit is configured to compute the
   concentration CNOX of the specific gas by using the measured value of the concentration CO2 of oxygen and the measured value of the sensor current I and by using the equation (1) [full equation not reproduced here]
   

Specifically, the examiner’s position was that the pending claim was unclear because “A and β are constants” and using A and β in equation (1) makes the scope of the claims indefinite under § 112(b) as any value could be used and the specification gave no specific values. The Appellant argued that “A” and “β” are defined as constants in the Specification, with β “determined in dependence upon the material of the diffusion resistance portion.”

The PTAB determined that the Office’s framing was incorrect. They explained that the specification did describe the nature of the constants and how they are determined, including that β is determined in dependence upon the material of the diffusion resistance portion. The absence of explicit numerical values did not render the claims unclear. Rather, the disclosure provided sufficient information such that a person of ordinary skill in the art could empirically determine appropriate values for a given sensor configuration. The Board held that to the extent the claims encompass any value of each recited constant, that is an issue of breadth rather than indefiniteness, and reversed the § 112(b) rejection on that basis.

This reasoning is consistent with long-standing examination guidance. Indefiniteness turns on whether claim boundaries are reasonably clear, not on whether the specification itemizes every possible instantiation. Enablement similarly tolerates calibration and empirical determination where the art permits it without undue experimentation, as reflected in MPEP § 2164 and its discussion of routine experimentation. When a skilled artisan can determine workable values through ordinary testing, the absence of numbers should not doom the claim.

There are several practical takeaways from this decision. First, when drafting specifications for inventions that rely on calibratable parameters, it is often sufficient—and strategically preferable—to explain how values are determined rather than to lock the invention into specific numbers. Second, when facing an indefiniteness rejection premised on missing numerical values, it may be helpful reframe the issue as one of breadth, not clarity, and to anchor the argument in what a skilled artisan can determine based on the disclosure. Third, expert declaration evidence may be helpful to confirm that a person skilled in the art could properly calibrate the values based on the teachings in the specification and their general knowledge.

Calibration is not indefiniteness, breadth is not ambiguity, and guidance in the specification matters. For patent professionals, the case provides both drafting insights and appellate ammunition when examination veers off course.

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