A diode is an electronic device that allows current to pass through it in one direction only and not in the opposite direction. Semiconductor diodes usually have a common structural principle, which is a P-type semiconductor block coupled with an N-type semiconductor block and connected to two output pins, namely: anode and cathode.
A rectifier circuit is an electronic circuit containing electronic components that convert alternating current into direct current. Rectifier circuits are used in DC power supplies or radio signal detectors in radio equipment. The rectifier circuit usually contains semiconductor diodes to control current and mercury rectifier lamps or other components.
In General, the best way to test a diode is to use the “Test Diode” mode on the multimeter because this mode directly pertains to the features of the diode. In this method, the diode is forward biased. A normally working diode will allow current to flow in forwarding bias and must have a voltage drop. If the displayed voltage value is between 0.6 and 0.7 (for Silicon Diode) then the diode is healthy and perfect.
Diode measurement steps by “Test Diode” mode
- Determine the positive and negative poles of the diodes.
- Keep the Digital Multimeter (DMM) in diode test mode. In this mode, the multimeter is capable of providing a current of approximately 2mA between the test leads.(2)
- Connect the black probe to the negative terminal and the red probe of the multimeter to the positive terminal.
- Observe the readings on the multimeter’s display. If the displayed voltage value is between 0.6 and 0.7 (for Silicon Diode) then the diode is healthy and perfect. For Germanium Diodes, this value ranges from 0.25 to 0.3.
- Now, reverse the meter terminals, and connect the black probe to the positive terminal and the red probe to the negative terminal. This is the reverse bias condition of the diode when no current flows through it. Therefore, the meter must read OL or 1 (equivalent to an open circuit) if the diode is healthy.
If the meter shows values unrelated to the above two conditions, then the diode(1) is faulty. Defects in the diode can be open or short.
In this article, we have detailed instructions on the “Test Diode” mode for diode measurement. We hope that the knowledge we provide will help you understand more about power tools.
(1) Diode Info – https://learn.sparkfun.com/tutorials/diodes/all
(2) Multimeter Info – https://www.electrical4u.com/voltage-or-electric-potential-difference/