(I) Instrument reading part
1 Appearance
1.1 Appearance and structure of the instrument shall be intact. Specific marks for the name, model, specification, measuring range, graduation number, manufacturer's name or brand, delivery number and manufacturing date shall all be indicated.
1.2 Exposed parts (terminal, panel and control gear, etc.) of the instrument shall be free from looseness and rupture; digital indication panel has no defects, which impact reading.
1.3 When the instrument inclines, the internal components shall not make noise for looseness.
1.4 Control gears and turn-buttons shall have corresponding functions and certain adjustment ranges in the prescribed status.
1.5 Values displayed on the instrument shall be clear and have even brightness and shall not overlap with each other, shall be free from un-brightness and lacking strokes; status display of decimal points, polarity and overload shall be correct.
2 Insulation resistances
Insulation resistances between power systems of the instrument, input/output, earthing terminal (or enclosure) (except that the input terminal does not isolate from the output terminal) at an environment temperature of 15~35℃ and a relative humidity of 45%~75% shall not be less than 20MΩ.
3 Insulation strength
At a environment temperature of 15~35℃ and a relative humidity of 45%~75%, test voltage specified in Table 1 shall be applied among instrument power system, input/output and earthing terminal (or enclosure) (except that the input terminal does not isolate from the output terminal) for 1 min and shall be free from voltage breakdown or flashover.
4 Basic errors
Allowable basic errors of the instrument have three express modes for absolute errors.
