1. The multimeter is adjusted to the diode; 2. First measure any two of the four corners to determine which two corners are conductive and which two corners are disconnected; 3. Press the button to measure any two feet. Judging which two corners are conductive, which two corners are open; 4. Starting to disconnect, the two feet of the button pressed can be used as the two corners of the welding. According to experience, generally only the pair Direct welding is possible with the corners. Note: The working principle of the button switch is that when the button is pressed, the two patches are close, that is, the switch is turned on; when released, the patch is separated, that is, disconnected.

The button is usually a switch for a control circuit that turns a small current on or off for a short time. The buttons are various in structure: knob type - operation by hand button rotation; indicator type - button can be installed into the signal display signal; emergency type - with mushroom-shaped button cap to indicate emergency operation. Buttons commonly used in machine tools such as the LA series. Mainly according to the number of contacts required, the type of contact and color selection.

The size of the switch is calculated based on its load capacity. The outlet switch calculates the loop current based on the calculated load of the loop. The total line switch calculates the current based on the total calculated load and selects the switch capacity. Note that the current must be calculated using the calculated load.