During operation, household appliances such as air conditioners, refrigerators, and induction cookers change their operating state frequently, resulting in a wide range of changes in operating current, which can drop from tens of amps to a few milliamps. General power measuring instruments only allow integral measurement at the same range. If the measurement value exceeds the current maximum range, the measurement result is inaccurate, and it is necessary to manually switch the range and then integrate, which is impossible to continuously carry out integration measurement of equipment with large dynamic current changes. The IT9120 series power meter can automatically switch the range in integration mode, which solves the integration measurement error caused by manual range switching and more accurately measures the power consumption of household appliances.