b) Several known methods of determining a parameter 

In both T 485/00 and T 225/93, three methods were known in the art for the determination of the specific surface area of a CaCO₃ particle. In neither case did the description or common general knowledge indicate a preference for one of them. In T 485/00, the board held that reproducing an example and measuring the surface area of the resulting product by two or three well-known methods did not represent an undue burden for the skilled person. In T 225/93, however, the board found that, as there were three different measuring methods which did not always lead to the same result, this amounted to an undue burden.

T 473/15 observed that the conclusions of T 225/93 could not be applied since in that case the principles underlying the possible methods of measurement were completely different from each other (permeability, photometry and adsorption), contrary to the case at hand, and in that case the parties agreed that the different methods yielded different results. On the contrary, in case T 473/15 the appellants (opponents) did not provide evidence for the presence of major deviations between the different definitions for fiber diameter.

In T 147/12, the objection of the appellant (opponent) was not that no method of determination of the alkali metal content in polyethers existed. Rather, the gist of its argumentation was that D7 (scientific publication), D8 (a study) and D11 (experimental report provided by the opponent) showed that the value obtained for the alkali metal content in the polyether depended on the analytical method used for its determination. The board stated that even if the conditions of measurement lead to variations of the value of the alkali metal content as argued by the appellant, this alone did not constitute a lack of sufficiency of disclosure regarding the claimed subject-matter as a whole since it had not been shown that the uncertainty concerning the alkali metal content affected the claimed process to such an extent that the skilled person wishing to perform the process would face an undue burden. The appellant had shown that the uncertainty concerning the method of determination of the alkali metal content meant that the skilled person could not ascertain whether the value he would obtain was within or outside the claimed range. It was, however, not shown that as a result of that uncertainty, the skilled person would fundamentally be prevented from obtaining a polyether according to claim 1. The board stated that T 83/01 (skilled person not in a position to perform any measurement of the claimed parameter) and T 815/07 (test method defined in claim 1 resulting in totally arbitrary values) were not applicable to the present case.

In T 345/16 the board considered that measuring a "particle size", a conventional parameter in the technical field concerned, would merely require selecting and applying any of the well-known methods used in the field, for which no undue burden or inventive skill would be required. The appellant (opponent) argued that the patent in suit did not include any information as to how the "particle size" should be measured, and that this would lead to significant inconsistencies in the results. The board was not convinced by this reasoning, since any possible inconsistency resulting from the choice of a particular measuring method (among a number of well-known available alternatives) would only affect the demarcation of the scope of protection and not the ability to carry out the invention. In this respect the board noted that, in line with a number of decisions in the case law (see e.g. T 378/11, dealing precisely with the parameter "particle size"), problems of demarcation had to be dealt with under Art. 84 EPC and not under Art. 83 EPC. Since the feature "particle size" was part of the claims as granted, the board was not competent to assess compliance with Art. 84 EPC (G 3/14). The board also noted that there was no requirement in claim 1 to measure the primary particle size and the agglomerate particle size simultaneously rather than sequentially. Furthermore, a number of well-known optical methods were available which would allow both a simultaneous (e.g. visual analysis of the agglomerated particles to estimate the size of the agglomerates and the primary particles identifiable in these agglomerates) and a sequential measurement to be carried out. In any case, the appellant had not provided any evidence in support of its allegations.

In T 1154/12 the respondent (opponent) contended that the patent lacked sufficient disclosure because it did not define the method which should be used for measuring and calculating the "average particle size" called for in claim 1. The board was not persuaded by this argument. It was undisputed that several methods of measuring or calculating the average particle size were conceivable to the skilled person. Whether or not the use of several kinds of measuring or calculating the average particle size led to different results was, however, a matter of determining the boundaries of the independent claim, i.e. a matter of clarity rather than sufficiency of disclosure (see T 378/11).

In T 2666/17 confirmed and summarised the findings in T 815/17 (problem if the parameter is ill defined) and noted that surface tension was a well-known parameter which could be measured using known methods. That the measuring method would lead to different results would not prevent the skilled person from reproducing the invention but would simply raise doubts as to whether certain embodiments at the margins of the scope of the protection fall within the forbidden area or not (issue of Art. 84 EPC).

In T 1960/14 (parameter – melting point of a palm oil fraction), the board stated that the skilled person (common general knowledge) was aware of three suitable standard methods. The respondent (opponent) asserted that these methods provided significantly different results but did not submit any experimental evidence. In view of tests disclosed in D22, the board concluded in agreement with the patent proprietor that all three methods provided very similar results with uncertainty only at the edges of the claimed ranges. T 1960/14 endorsed the finding in T 608/07 that for an insufficiency arising out of ambiguity it is not enough to show that an ambiguity exists, in this case at the margins of the claimed melting point range due to the lack of any indication of the measuring method. It will normally be necessary to show that this ambiguity deprived the skilled person of the promise of the invention. In the case at issue, the respondent (opponent) had not submitted any technical evidence to that effect. The respondent in T 1960/14 also referred to T 575/05 and argued that in a similar situation a board had decided that although standards were available, the patent did not provide sufficient guidance as to which one should be used (invention insufficiently disclosed). However according to the board in T 1960/14, unlike in T 575/05, where many commonly used but not clearly defined methods of determining a parameter were available and thus led to a high degree of uncertainty for the skilled person trying to carry out the invention, at the priority date of the patent in suit there were only three clearly defined standard methods of determining the melting point of palm oil fractions, which produced very similar results with a fairly minor degree of ambiguity/uncertainty only at the margins of the claimed range. The issue of Art. 84 EPC was also addressed (T 256/87 and T 815/07 not followed).

In T 786/15 numerous methods of measuring the parameter Tg existed and the skilled person was aware of three ways, but the patent did not indicate any method for its measurement. To determine whether the Tg parameter was "so ill defined", it had to be investigated which methods would be considered by the skilled person. Referring to T 608/07 (point 2.5.2 of the Reasons), the board concluded that the alleged ambiguity arose at the edges of the values recited in claim, but this in itself could not lead to a finding of insufficiency of disclosure.

See also in this chapter: T 492/92 (two methods suggested by applicant) and T 1414/08 (parameter tensile strength – paper - not considered unusual – but no specific method of measuring disclosed – several standardised test methods in the art – consequences – end values ambiguous – scope – issue of Art. 84 EPC).