CISPR has published the limits on the noises emitting from power lines and signal lines. But different measurement environment and measurement methods are used in every countries. This difference causes much confusion in understanding the results measured by different test laboratories. In this paper, we measure EMI noise using the absorbing clamp method that takes short measurement time and is described in CISPR 13, 14-1, 16-2. We analyze the cause of the difference of measurement results and propose the method for improving the uncertainty