This regulation is applicable to initial verification, subsequent verification and in-service inspection of direct acting indicating analogue DC and AC (with frequency of 40 Hz~10 kHz) amperemeters, voltmeters, wattmeters and ohmmeters (with resistance of 1 Ω~1 MΩ), as well as multimeter for measuring current, voltage and resistance (hereinafter referred to as instrument).
This regulation is not applicable to verification of automatic recording instrument, digital instrument, electronic instrument, mean voltmeter, peak voltmeter, leakage current meter, three-phase wattmeter and electrostatic voltmeter with voltage above 600 V.
2 Normative References
JJF 1001-1998 General Terms in Metrology and Their Definitions
JJF 1059-1999 Evaluation and Expression of Uncertainty in Measurement
GB/T 7676.1~7676.9-1998 Direct Acting Indicating Analogue Electrical Measuring Instruments and Their Accessories
While applying this regulation, attention shall be paid to that the currently valid versions of the above references are applied.
3 Overview
An instrument is composed of measuring circuit and measuring mechanism. When the measurand becomes acceptable by the measuring mechanism via the measuring circuit, it will actuate the measuring mechanism, thus indicating the magnitude of the measurand.
The commonly used instruments may be classified, by the driving mode, into permanent-magnet moving-coil instrument, moving-iron instrument, electrodynamic instrument, electrostatic instrument and rectifier instrument, etc.
4 Metrological Performance Requirements
4.1 Accuracy Class
The accuracy class and maximum permissible error (i.e. fiducial error) of instrument shall be in accordance with those specified in Table 1.
Table 1 Accuracy Class and Maximum Permissible Error
Accuracy class 0.1 0.2 0.5 1.0 1.5
Maximum permissible error (%) ±0.1 ±0.2 ±0.5 ±1.0 ±1.5
Accuracy class 2.0 2.5 5.0 10 20
Maximum permissible error (%) ±2.0 ±2.5 ±5.0 ±10 ±20
4.2 Basic Error
4.2.1 The basic error of the instrument, on all scale marks within the measuring range (effective range) of the scale, shall not exceed the maximum permissible error specified in Table 1.
The basic error of instrument is expressed by fiducial error and calculated according to Formula (1).
