A diode blocks the current from flowing in one direction and allows it to pass through when the opposite is true.A digital multimeter with a diode check function will give the best results if you want to test whether it is functional.When exposed to too much power, the design of most modern diodes can break down.
Step 1: Check for a checking mode.
A lot of digital multimeters have a check mode.The symbol for "diode:" is a black arrow pointing to a vertical line.Resistance should be tested if your multimeter doesn't have this mode.
Step 2: The power to the circuit should be turned off.
All power to the circuit should be turned off.To make sure there is no charge, you need to test the voltage.Continue if the voltage reading is zero.Capacitors may need to be discharged in the circuit if the power is off.This should not be attempted by novices.You may need to remove the diode from the circuit completely if it's connected to other components in parallel.Once you're done testing, this usually requires desoldering.
Step 3: The function can be selected.
The dial should be turned back to check mode.Touch the leads together and listen for a tone that indicates continuity.Double check that your multimeter is set up correctly if you don't hear anything.The function is working if you hear a tone.Continue until you reach the next step.The current produced in this mode is too small to damage typical components.
Step 4: The positive and negative sides of the device are identified.
The two ends of the device are not the same.The negative end is usually marked with a stripe.The positive end is usually left out.The manufacturer's guide can be found if you use a different labeling system.You can conduct the tests and look at the results to see which one is the cathode.
Step 5: The forward bias of the device can be tested.
A positive charge is flowing from the anode to the cathode.The red and black leads are on the anode side of the wire.If the result is between 0.25 and 0.8 volts, the diode is working.It is possible for some multimeters to indicate continuity.All current flow is blocked by a result of OL.The next test needs to be looked at first.It's possible that you hooked up your multimeter in the wrong direction.The diode may be shorted if the result is less than 0.4 volts.With the next test, confirm this.
Step 6: The reverse bias must be tested.
There is a positive and a negative charge on the side of the device.Current flowing in this direction is prevented by dios.Change the position of the leads to see if this works.The red and black leads should be next to each other.A result of OL means the diode is blocking the current.It means you've made a mistake.The forward bias is being tested.You should have a result of the previous test.If the test shows the same result as the forward-biased one, the diode needs to be replaced.If the test is successful and the forward-biased result is less than 0.4 volts, you may be working with a germanium diode.
Step 7: This method is used when necessary.
The diode check function is more accurate than this method of testing.If you use a digital multimeter without a diode check function, follow these instructions.
Step 8: The multimeter should be set to resistance mode.
The resistance mode is usually marked with the symbol.This may be labeled R on some older models.Some digital multimeters only have one setting.
Step 9: The leads should be plugged in.
The COM port has a negative lead.The red and black leads are positive on most digital multimeters.The red or black lead can be used as the positive lead.Check your manual for the setup of your multimeter.
Step 10: The device needs to be disconnected.
If the diode is connected to a circuit,resistance tests can give incorrect results.
Step 11: The forward bias can be measured.
The negative lead is marked with a stripe.Touch the positive lead.A low resistance value is what a working diode should have.The resistance range on your multimeter dial should be lowered if the result is zero.If the result is still zero, you may have a problem.The remaining tests can either confirm or deny it.The exact quantity is not useful for circuit design as it is influenced by many factors.You can get a different result on a second multimeter, but it should be in the same range.
Step 12: Take the reverse bias into account.
You can set your multimeter to a high resistance range.If you reverse the position of the leads, the negative lead will touch the anode.The resistance should be very high since diodes block current in this direction.It is too high to measure a resistance in the hundreds of K, or an over limit reading, meaning it is working.A result of zero means the diode needs to be replaced.If you get the same results in both directions, the diode is broken.
Step 13: If you compare it to a working device, you'll see that it's not as good.
If you know the workings of a new Silicon Diode, you should try it.The diode is most likely functional if you get similar results.If you still have issues with your circuit, it's a good idea to buy a multimeter with a diode check function.The digital multimeter most likely isn't producing enough current for an accurate test if your forward-bias result is zero.Try again with a multimeter.
Step 14: The forward voltage should be measured accurately.
The check function doesn't give enough current to find the actual forward voltage in the circuit.If you want to confirm that you have the intended forward voltage of 0.7V, you need to connect the positive terminal of the battery to a Resistor.You need to connect the other end of the resistors.The battery has a negative terminal.The forward voltage is measured.
Step 15: Understand the peak inverse voltages.
The PIV is the maximum reverse voltage that a diode can resist before it breaks.It's not practical to test this quantity because of the breakdown.The exception is designed to regulate the voltage and resist excess current.The PIV of a typical rectifier is around 50V, but there are models that can tolerate hundreds of volts.
Step 16: The zener diode has a PIV.
Zener diodes are not useful if you don't know what the voltage is.Find a variable power supply and confirm that it is turned off by setting up this circuit.The power supply has a positive terminal.You need to connect the other end of the resistors.The power supply has a negative terminal.The multimeter leads should be connected to measure reverse voltage across the diode.To turn on the variable power supply, set it to its lowest setting.While watching the multimeter, gradually increase the power supply.As power increases, you've found the breakdown voltage.If you don't increase the voltage, the diode could be destroyed.