Type DDS7172 single phase DIN rail watt-hour meter is a kind of new style single phase electronic watt-hour meter, it adopt micro-electronics technique, and imported large scale integrate circuit, use advanced technique of digital and SMT techniques, etc. The meter completely accord with relevant technical requirements of class 1 and class 2 single phase energy meter stipulated in National standard GB/T17215-2002 and international standard IEC61036. It can accurately and directly measure 50Hz or 60Hz active energy consumption from single phase AC electricity net., it can display total energy consumption by step type impulse register.