Electrical performance:Standard test conditions: temperature 20 Celsius, humidity 70%, if there is no difference in the test results, the test can also be performed at normal temperature and humidity.Current sensitivity:Pointer from zero scale to maximum scale (full scale position) Sensitivity 250 uA ± 10 % Internal impedance: 650 ohm ± 10 %.Insulation resistance: 500V DC plus 50M ohm or more compatible with the outer box of the meter and the electrical circuit. The insulation resistance of the meter housing and the electrical circuit is tested by 500V DC voltage.Zero position: the standard position of the meter is used, and the point where the front of the pointer and the centre of the zero scale are unified is the reference pointer and the zero scale overlap. The tolerance is ± 1mm. Balance: The allowable error range of the meter when the standard position is tilted 90 degrees forward and backward is ± 1mm.The pointer sticks: When the full-scale current triples the overcurrent in an instant and slowly reduces to the current sensitivity reading of 1/2, the pointer will return to the scale of 1/3 of the scale.Friction: When the current is added to the meter and slowly increased or decreased to a certain value, the error range of the indicated point is ± 1mm. Braking: instantly add 2/3 of the current value of the scale plate, within one second from the start to the position indicated by the pointer Special Test: Overload test: input ten times the full-scale current every five seconds, the action is repeated nine times. Each time is 0