2. Correctly connect the measuring circuit. The direction of the rotating torque of the electric measuring mechanism is related to the direction of the current in the two coils. In order to prevent the pointer of the electric power meter from deviating, the terminal button marked with "·" on the current coil of the power meter is connected. It must be connected to the positive side of the power supply, while the other end of the current coil is connected to the load, and the current coil is connected to the circuit in series.
3. Correct reading. Generally, the installed power meter is a direct-reading single-quantity program, and the number on the meter is the power number. When reading, first calculate the number of watts per grid (also known as the power meter constant) c according to the selected voltage range u, current range i, and the number of divisions at the full scale of the scale, and then multiply it by the pointer deflection The measured power p can be obtained after the number of grids.