New data acquisition technologies, such as phasor measurement units (PMU), have been implemented in recent years to operate the power system with more reliability and control by improving the protection schemes like line differential protection or damping the inter-area oscillations. The present standard IEEE C37.118 only provides general information about the testing conditions and requirements, without giving any specifics.. To create the PMU data function for the applications and thereby make the power system more reliable, the appropriate PMU test standards have to be developed and disseminated. Future testing methods should ensure that units from different manufacturers are tested identically and function properly under different repeatable test scenarios and test stand set up conditions. This paper presents experiences from tests of PMU accuracy and calibration conducted in Europe and the USA, which will facilitate the development of future standards. The test stand itself and the test results from the various PMU manufactures are presented, compared and discussed in this paper, taking into account the standardization issues.