**7.4 Conclusion**

The uncertainty evaluation is discussed to measure phase difference by applying DFT to sampling data in NIPS. The step-up procedures are described for the voltage dividers and shunts. The phase shifts and their uncertainties are given. The uncertainty of the phase shift in the fundamental is 13 rad (*k* = 2) for the 120 V divider, and 12 rad (*k* = 2) for the 5 A shunt. These specifications fall under the special frequency characteristic. They are discussed further when the results are applied to harmonic power measurement.
