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The Best Ways to Test a Diode in A Circuit

The diodes are highly crucial for the efficient performance of consumer electronics. Your microwaves, ACs, fridge, and washing machines might fail to impress and satisfy you if one of their diodes is not working properly.

Due to this reason, you might sweat without your AC during a hot summer day and might have to stay famished due to a dysfunctioning microwave all day long. Defects in consumer electronics directly impact your life. You can never afford a malfunctioning diode at all since it keeps the electronics on track.

What is a Diode Test?

First, you need to know what a diode is. So a diode is a small part of any circuit that makes the current follow a single direction to flow. With diodes, the current does not follow multiple directions, which can be harmful to the electronic’s performance.

Therefore, a diode has to be in an efficient state to support the electronics. To make sure of this, we do a diode test. Such tests are important and help you identify possible defects in the diodes before you integrate them into the system. You can use multimeters which are a common way to analyze the diode’s performance.

Why is there a failure of the Diode in A Circuit?

Now let’s see why a diode undergoes failure:

  • Open circuits
  • Short circuits
  • Peculiar voltage regulation
  • Unbalanced output
  • Supply voltage touches 0
  • The surge in power supply voltage

Testing Diode with Methods in A Circuit

We have discussed a little bit about using the multimeters for diode testing. You must know that you can rely on a multimeter for the onboard and without board monitoring. You need to know that you can only draw positive results from diode testing on two conditions.

You have a deep understanding of the working of a diode, plus you are good with recording the data since there is no margin of human error when you are doing the measurements. Also, experts believe that an analog multimeter is reliable for giving precise figures to users. The diode tests never work out effectively without a thumb rule. Let’s learn about it below:

Thumb Rule: You will need to record the PN junction’s forward and reverse resistances individually so that you can analyze these figures later during the diode testing. 

Testing Diode in A Circuit Via Analog Multimeter

When you are using analog multimeters, you will be at ease. These don’t have a technical testing mode that will bounce over your head. However, we recommend using it by keeping it on the mode of resistance. Now that you have done these settings, you can use this multimeter for PN junction testing. Don’t worry; the following steps will make it much easier for you:

  • Adjust the multimeter for low resistance.
  • Now its time to join the terminals of the multimeter with the diode
  • Make sure to connect the + terminal to the anode and the – terminal to the cathode when you are assembling the setup for testing.
  • This setup is in the forward-biased state. Remember that
  • Use a reliable diode for testing when you are using a multimeter at low resistance.
  • Now change the connections so that your setup will switch to reverse biased condition.
  • The OL reading will show that your diode is working in high opposition, which means it is in an optimum state.
  • In the absence of the OL reading, your diode is not accurate.


Testing Diode in A Circuit Via Digital Multimeter

A digital multimeter allows you to use it in 2 modes. You can switch the nature of this multimeter into ohmmeter mode and diode mode. It means a digital multimeter has two basic functions to serve. You can use it as an ohmmeter and a diode, as per your case. You should know this because sometimes we need to test multiple devices. In this case, a digital multimeter will come in handy since it will save time and fasten up the testing process. 

Testing Diode in A Circuit Via Diode Mode


The diode mode on the multimeter works by recording the voltage fall throughout the diode. Remember, this only works when your diode is in an onward bias. However, if you do not know how to use the meter on diode mode, we are going to let you know through the following steps:

  • Determine the cathode and anode sides of the diode you are testing.
  • Now adjust the mode of a diode on your digital multimeter.
  • After this, you should know that in diode mode, the meter will give some amount of current to the diode beneath testing.
  • Now join the terminals with the diode to establish the forward bias condition.
  • If you are using a silicon diode, it will give a reading in the middle of 0.6 and 0.7, which is different from Germanium. 
  • Also, check the diode in reversal biased state and note the OL reading; if its OL reading marks 1, it means you are diode is fine.

Testing Diode in A Circuit without Using Multimeter

Sometimes defective diodes get some markings that indicate the state of the diode right from the circuit. You can easily detect the problem in this way, but this is not the case every time. However, you can still detect the defects of a diode without using a multimeter. Don’t know the trick yet? Here’s how:

  • You can rely on continuity circuit tests and component tester techniques instead of using a multimeter.
  • Now you need to learn how these methods work and then fix your diode under testing in a firm position.
  • In the forward-biased condition, the LED present in the circuit will flicker, meaning it is fine when you are doing continuity circuit testing.
  • In the reverse biased state, the LED won’t flicker, meaning the diode is defective.
  • For the component tester method, if the reading marks VF, then consider your diode to be healthy.

Wrap Up!

Diodes are highly inevitable for the fine performance of consumer electronics. Problems with diodes mean your entire electronics are at stake. They would fail to perform naturally and will undergo technical glitches, electrical faults, heat damage, and whatnot! For this reason, diodes have to be in an optimum state, and to ensure this; we use different diode inspection methods.

You can use a multimeter, component tester, and also continuity circuit testing. We have described all the important aspects of diode testing in this detailed guide. You have tons of options available for diode testing, but we recommend relying on these three whenever you need to test your diode. 




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