Most medical X-ray machines are controlled by foot switch. The foot switch is made of a shell made of iron, aluminum alloy or non-metallic insulation, and is composed of one or two sets of contacts. The insulating pressure rod presses the contacts together. After the foot is lifted, the pressure rod reset contact is disconnected due to the force of the spring. The following are common faults of the foot switch.
1. Poor contact or no contact
1. See through the high-voltage primary relay not working or trembling when working;
2. A small number of X-ray machine foot switches have two sets of contacts, one is for connecting high-voltage primary circuits; the other is connected with anti-surge resistors. If the former is in poor contact, in addition to no X-rays, a surge resistor will be inserted into the circuit, which will not only reduce the high-voltage primary voltage and weaken the X-rays, but also the resistance will heat up abnormally, and it will be burned soon;
(2) Cause analysis
1. The contact reed is disassembled, deformed or loses elasticity, or the reed fixing screw is loose, making its position incorrect;
2. The spring force is too large, and the pressure rod cannot be pressed or the contact is not tightly pressed;
1. Open the shell, replace the disassembled reed, rebuild the deformed reed, tighten the loose screw, and adjust the position of the reed;
2. Extend the spring forcefully to reduce the elastic force.
2. Leakage of foot switch
1. The foot switch with a metal shell will feel numb or electric shock when the human body touches the shell of the foot switch;
2. When the foot is not stepped on the foot switch, X-rays will be generated when the switch is turned on, and the two leads of the foot switch with a multimeter in the ohm position are indicated.
(2) Cause analysis
1. The fixing screw of the contact reed is loosened, so that the contact or the reed can touch the shell;
2. Because the temperature of the arc extinguishing resistance is too high, the material insulated from the ground will be burned, causing electric leakage;
3. Moisture or water has entered the foot switch.