Devices (e.g. measuring instrument or measuring devices) on which the error and also the effects in defined test conditions are within defined limits; they can have a class identifier that mostly corresponds to a the value in % of the actual value or of the end value.
Example for electrical measuring instruments: 0.1 — 0.2 — 0.5 — 1 — 1.5 — 2 (VDI 2600).