Can you use competent in the context of an inanimate object such as an instruction manual, or a voltmeter?
e.g. "In my opinion Standard 12345 is considered a competent document." or "The potentials can easily be measured using a competent voltmeter."
Thank you.
I would say that competent is primarily associate with acquired skills. For something to be competent, perhaps consider whether it can also be incompetent. I think you would be better off using a more applicable synonym such as "sufficient", "adequate", or "functional". You wouldn't say you had an incompetent voltmeter, instead you would say you have a non-functioning voltmeter. And a set of standards would be adequate to manage a procedure.
However here is an example of how you may be able to use it in terms of the Standards document.
1.3(Chiefly of a court or other body) accepted as having legal authority to deal with a particular matter. Example: the governor was not the competent authority to deal with the matter. Link
You could, but I don't think it would be really correct. While competent can be used with inanimate objects, they're typically bodies made up of people who collectively exhibit that competence, e.g. a competent body, a competent committee, a competent government (no laughing at the back there!).
I think you'd be better off with suitable, appropriate or similar.
Suitable: Right or appropriate for a particular person, purpose, or situation
and
Appropriate: Suitable or proper in the circumstances
