Abstract: ：The period measuring method counts the total number of high frequency pulses during certain period of time to obtain the frequency of input signal. The regression method takes into consideration the numbers of pulses counted during each individual short interval. Regression method can improve resolution, but the analysis and conclusions presented by Staffan Johansson are not correct in the world at present. Correct analysis and conclusions are presented in this paper and verified by experiments. Analysis and experiments show that the regression method is superior to the period measuring method when the number of counted input cycles is greater than 36 and the regression method will have better performance as the number of counted input cycles grows larger.

Key words: frequency measurement, linear regression, resolution