In order to solve the problem that the performance of the grating card in the active volume tube flow standard device is not stable and sometimes the data cannot be locked, a method of measuring the standard volume value by using a counter instead of the grating card is proposed. The active volume tube uses grating ruler as the measurement standard. According to the characteristics of grating ruler signal, double timing method is adopted to realize grating ruler signal acquisition. The problem of missing pulse in signal acquisition is solved by using the self-made synchronous circuit and ADAM4080 counter, which ensures the accuracy of flow measurement. The experimental results show that the difference between the developed system and the original system in standard flow collection is less than 0.005%, which verifies the feasibility of the scheme.