Figure of Merit (FOM): Difference between revisions
imported>Lorenzo (Added a little info about what FOM says (and not says) about tube specs) |
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A FOM number gives an indication of a tubes quality and usefulness but is not to be taken as a tell-all-end-all as a full spec sheet gives far more detailed insight as to a tubes performance albeit it might seem slightly more esoteric to people who are unfamiliar with interpreting a spec-sheet. | A FOM number gives an indication of a tubes quality and usefulness but is not to be taken as a tell-all-end-all as a full spec sheet gives far more detailed insight as to a tubes performance albeit it might seem slightly more esoteric to people who are unfamiliar with interpreting a spec-sheet. | ||
In order to fairly judge a | In order to fairly judge a tubes FOM rating one should have some knowledge of the category to which a tube belongs as well as an average or minimum number for at least one of the factors involved in producing a FOM rating. If one knows that a particular category of tubes has a minimum SNR of 30 with average at 36 then going by FOM alone when considering an individual tube of that category is less arbitrary | ||
=== Mathematic formula === | === Mathematic formula === | ||
Revision as of 09:57, 25 August 2022
FOM (Figure of Merit) is the product of the Resolution and the Signal-to-Noise_Ratio_(SNR). It's dimensionless.
It was introduced as an arbitrary reference and shorthand overall performance grade for classes/groups of tubes and individual specimens to facilitate comparison and what performance can be expected.
A FOM number gives an indication of a tubes quality and usefulness but is not to be taken as a tell-all-end-all as a full spec sheet gives far more detailed insight as to a tubes performance albeit it might seem slightly more esoteric to people who are unfamiliar with interpreting a spec-sheet.
In order to fairly judge a tubes FOM rating one should have some knowledge of the category to which a tube belongs as well as an average or minimum number for at least one of the factors involved in producing a FOM rating. If one knows that a particular category of tubes has a minimum SNR of 30 with average at 36 then going by FOM alone when considering an individual tube of that category is less arbitrary
Mathematic formula
The formula is:
FOM=Resolution*Signal-to-noise ratio
As Resolution and SNR are two important numbers it is fair to say that a higher Figure of Merit is a fair indication of a particular tubes performance in general, but it is not possible to deduce from the number alone the individual number of either factor.
