In the lines of power generation, transformation, transmission, distribution and electricity consumption, the currents vary greatly, ranging from a few amperes to tens of thousands of amperes. In order to facilitate measurement, protection and control, it needs to be converted into a relatively uniform current. In addition, the voltage on the line is generally relatively high, such as direct measurement is very dangerous. Electrical Current Transformer plays the role of current conversion and electrical isolation. The mini-Electrical Current Transformer is also called the "Electrical Current Transformer". The meaning of "Electrical Current Transformer for Instrument" is that the multiple current ratio precision Electrical Current Transformer used in the laboratory is generally used to expand the range of the instrument.