**5.2.1 Digital Voltage Meter**

156 Modern Metrology Concerns

0 100 200 300 400 500

Sampling point

When Eq. (3.1.1) expresses a non-sinusoidal voltage signal and Eq. (3.1.3) denotes the sampling data under the sampling model of Eq. (3.1.2), the DC voltage, fundamental voltage, and harmonic voltage components can be obtained after calculation according to

1 11 arctan( / ) *<sup>V</sup>*

arctan( / ) *Vk k k*

where φ*V*1, φ*Vk* are the phase angles (against a reference time point) of the fundamental and

The experimental determination of the technical specifications of the NIM harmonic power

The frequency characteristic of the standard equipment can be initially determined by adopting the existing National AC Voltage Primary Standard for thermo-converters. In this process, the stable sinusoidal signals are exported at the selected frequency points that correspond to the fundamental, 10th, 20th, 30th, 40th, 50th, and 60th orders. Their amplitudes

standard equipment is discussed next, beginning with harmonic voltage.

*V a* 0 0 , (5.1.1)

2 2 *V ab* 1 11 , (5.1.2)

2 2 *V ab k kk* , (5.1.4)

*b a* , (5.1.3)

*b a* , (5.1.5)

Fig. 4.2.1. Waveform of the characterizing signal.

**5.1 Determination of harmonic voltage** 



0

Voltage/V

5

10

Eq. (3.3.7). These are expressed as follows:

harmonics, respectively, and *k* = 2,3,…*w*.

**5.2 Frequency characteristic** 

**5. Traceability of harmonic voltage and its uncertainty** 

Two DVMs (one for voltage, and another for current) are tested. The input range of 0.8 V is set as the test voltage. The DVMs are self-calibrated in advance through short input operation, and are connected to the reference voltage.

The results indicate that both DVMs have similar characteristics. The relative differences/errors ( *Vk*/*Vk* ) are

less than 1 V/V at the fundamental , less than 10 V/V within the 50th order, less than 20 V/V at the 60th order. Their standard deviations are all less than 3 V/V.
