A diode is an electronic device with two terminals that conducts electric current in one direction and blocks it in the opposite. Sometimes it can also be called a rectifier and converts alternating electricity into DC. Since the diode is essentially "unidirectional", it is important to distinguish the two ends. You can understand the orientation of this device by looking at the marks on the diode itself, but if these are worn or not present, you can use a multimeter.
Steps
Method 1 of 2: Check the Signs
Step 1. Understand how a diode works
This is composed of a P-type semiconductor combined with a N-type semiconductor. The second represents the negative end of the diode and is called the "cathode". The P-type semiconductor is the positive end of the diode and is called the "anode".
- If the positive side of the electrical voltage source is connected to the positive end (anode) of the diode and the negative side of the source is connected to the cathode of the diode, then the latter will conduct electricity.
- If the diode is upside down, the current is blocked (up to the limit).
Step 2. Learn the meaning of the diode schematic symbols
This device is indicated, in the wiring diagrams, with the symbol (- ▷ | -) which shows how the diode itself must be installed. The symbol consists of an arrow indicating a vertical bar beyond which a horizontal segment continues.
The arrow indicates the positive end of the diode, while the vertical bar represents its negative side. You can imagine how the current flows from the positive side to the negative and the arrow indicates the direction of this flow
Step 3. Look for a larger band
If there is no schematic symbol printed on the diode, look for a ring, band, or line stamped on the body of the device. Most diodes have a large colored band near the negative end (cathode). The band runs the entire circumference of the diode.
Step 4. Identify the anode of an LED
The LED is nothing more than a diode that emits light and you can identify the positive end by looking at the two "legs". The longest is the positive pole, the anode.
If these two tips have been cut, check the outer casing of the LED. The tip closest to the flat edge is the negative pole, the cathode
Method 2 of 2: Using a Multimeter
Step 1. Set the multimeter to the "Diode" function
It is usually indicated by the schematic symbol of the diode (- ▷ | -). This mode allows the multimeter to send current through the diode making it easier to verify.
You can still test the diode even without the specific setting. In this case you have to use the resistance function (Ω)
Step 2. Connect the multimeter to the diode
Join the positive clamp to one end of the diode and the negative one to the other. You should be able to read values on the meter display.
- If you have set the multimeter to “Diode”, you will be able to read the voltage, if the terminals of the instrument are connected in a manner consistent with the diode; otherwise, you will not get any reading.
- If your instrument does not have the "Diode" function, then you will read a low resistance when the positive terminal is connected to the anode of the diode and the negative terminal to the cathode. If the connection is "incorrect" then you will read a very high resistance value which is sometimes expressed as "OL" (overload, overload).
Step 3. Check an LED
This is a diode capable of emitting light. Set up the multimeter with the “Diode” function. Connect the positive terminal to one of the "legs" of the LED and the negative one to the other. If the LED lights up, then the connection is consistent (positive terminal on the anode and negative terminal on the cathode). If the light does not come on, the terminals are reversed.
