Good question. I am for a movement that demands that sensor size be described in mm by mm and not by alphabet soup (CMOS, CCT and the like); or fractions (1/1.7"--a half century old method of measuring TV sensors). There must be at least half a dozen ways to state sensor size, all different. Thankfully, there are a few sites that explain all this with graphs, etc. I appreciate those, but do not appreciate the need for those. I suppose also there are cameramen who love to keep the secret of photography as arcane as they can, as it's something to talk about when you're not taking pictures.
But to answer your question as to how big a sensor is 1/2.3", I really don't know.