Common formulas for measuring diodes and capacitors with multimeters
1. Measure the polarity and quality of the crystal diode
To determine the polarity of the diode, turn the multimeter to the thousand-ohm range. The measured resistance value is small thousand ohms, the diode forward resistance. The black pen touches the positive pole of the tube, and the red pen touches the negative pole of the tube.
The measured resistance is tens of thousands of ohms, and the diode reverse resistance. The red pen touches the positive pole and the black pen touches the negative pole.
To judge whether the diode is good or bad, turn the multimeter to the thousand ohm gear. The difference between positive and negative resistance values is large, and the larger the value, the better. The positive and negative resistance values are close, and the tested tube has failed.
The positive and negative resistance values are both zero, and the two poles of the tube are short-circuited. The positive and negative resistance values are infinite, and the inside of the tube has been opened.
2. Check whether the capacitor is good or bad
Microfarad capacitors are easy to measure. Dial the multimeter to the thousand-ohm range, and connect the red and black test pens to the two poles. The needle swings left and right once, and the larger the amplitude, the better.
The needle does not swing at all, and there is an open circuit in the capacitor under test. The needle does not return to zero, and the capacitor under test has broken down.
3. Digital multimeter buzzer block to detect the quality of electrolytic capacitors
The quality of electrolytic capacitors is detected by a digital multimeter. Turn the switch to the buzzer, and the red and black brushes touch the positive and negative poles. A short beep sounded, then the overflow symbol was displayed.
The buzzer sounds for a long time and the capacitor capacity is large. If the buzzer keeps ringing, the capacitor under test is short-circuited. If the buzzer does not sound, the capacitor is internally disconnected.
4. Detect the quality of high-voltage silicon stack
Check the quality of the silicon stack, and turn the multimeter to the voltage level. Silicon stack multimeters are connected in series, across AC two hundred and two. The range is DC 250, and the silicon stack is connected in the forward direction.
More than 30 volts are qualified, and the needle does not move and there is a fault. The range is AC 250, and the reading is 222 short circuit. The needle does not move and reads zero, and the silicon stack has an open circuit.
