How to Check a Capacitor Value with a Digital Multimeter

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A capacitor that used to be called a condenser is a passive electrical part that is utilized to “store electricity” in the form of electrical charge. You will find numerous types of capacitors accessible, from small capacitor beads utilized in resonance circuits to big power factor correction capacitors. Nonetheless, they all do the same thing: store charge. 

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The simplest and most basic type of capacitor has two parallel conductive plates divided by a good insulating material we call the dielectric. Because of that insulating power, the DC power can’t flow through the capacitor because it stops allowing it. Instead, a voltage to be present across the plates in the form of an electric charge.

Such conductive plates could be either cylindrical, rectangular, and circular in shape, with the dielectric insulating layer being air, plastic, paper, or waxed or some form of a liquid gel as utilized in electrolytic capacitors. 

Different Types of Electrical Charge 

You will find two types of electrical charge: negative charge in the form of electrons and positive charge in the form of protons. The positive charge immediately accumulates on one plate if a voltage is placed across a capacitor. Meanwhile, a corresponding negative charge builds upon the other plate. For each particle of positive charge arriving at one plate, a charge of the same sign will leave from the negative plate. 

The plates then remain charge-neutral as a potential difference, as the charge is created between two plates. The quantity of probable difference present across the capacitor depends upon the amount of charge placed onto the plates by the work being performed by the source voltage and by how much capacitance the capacitor has. 

The Capacitance Value

 Capacitance is the electrical property of a capacitor and the measure of a capacitor’s capability to store an electrical charge into its two plates. When a voltage of volts is attached across the capacitors, two plates of positive electrical charge in coulombs are present on one plate and a negative electrical charge on the other.

The capacitor will have a capacitance value that is equal to the amount of charge divided by the voltage across it, providing you the equation of C = QV along with the value of the capacitance in Farads. Nevertheless, the Farad on its own is a big unit. Hence, sub-units of the Farad are normally utilized to denote a capacitor value such as:

  • pico-farads (pF)
  • nano-farads (nF)
  • micro-farads (uF) 

The capacitance of a capacitor is equivalent to the ratio of charge per plate to the applied voltage. However, it also depends on the distance and physical size between the two conductive plates. For instance, there would be more surface area for the charge to build upon, providing a higher value of capacitance if the two plates were bigger or multiple plates were utilized.

Similarly, when the distance between the two plates is closer or a different type of dielectric is utilized, more charge will result in a higher capacitance. The capacitor’s capacitance can also be stated in terms of its physical size, the type of dielectric utilized, and the distance between the two plates. 

How Do You Check the Value of a Capacitor? 

From giving flexible filter choices to safeguarding delicate microchips from noise to controlling a voltage increase to power shortage, keeping a continuous power supply, to decoupling, you will find various uses for capacitors in a circuit.

Keep in mind that these capacitors could get ruined because of different factors such as:

  • moisture 
  • chemical contamination
  • humidity
  • high voltage
  • heat
  • aging 

Failing capacitors are one of the typical reasons for electronic and electrical malfunctions. Nonetheless, you need to catch a malfunctioning capacitor right away. A simple way to do that is by using a digital multimeter. 

Nonetheless, how do you determine whether a capacitor is defective or just working perfectly? How do you test the capacitor efficiently and smoothly with a digital multimeter? You can determine a capacitor’s value and learn whether it’s faulty or not by just doing a basic visual check. 

One of the signs of a malfunctioning capacitor is a bulging or swollen top or bottom. Make sure you check the capacitor’s casing as well as the printed circuit board to determine whether it’s damaged or discolored. Another sign of a faulty capacitor is the presence of a leaky electrolyte.

Change your capacitor immediately, especially if you encounter any of such noticeable signs. Follow the steps below to check the capacitor’s value with a multimeter.

  • For the first step, ensure your capacitor is properly discharged. One of the key functions of a capacitor is to store power. Hence, it can cause injuries or burns if you don’t discharge its property before dealing it for testing. 

For this step, you’ll need a capacitor discharge tool like a metal object like a screw to discharge a smaller capacitor or a bulb for a high voltage capacitor. 

  • Now, set your multimeter in a high Ohm range. The appropriate meter reading should be more than 1000 ohms = 1K. 
  • For the third step, attach the leads to the terminals of the capacitor. For your polarized connector, attach the black probe to the negative terminal and the red probe to the positive terminal. What about if you have a non-polarized capacitor? You can attach it either way.
  • Now, write down the resistance reading. Your meter will begin showing a reading from 0 and will move towards infinity. Further, it will stop at a digital resistance value and go back to the Open Line. Remember the reading and determine whether its reading is nearer to the resistance value specified on your capacitor. 
  • Repeat the above steps. Your capacitor is a good one if the test shows the same result when repeated. Nonetheless, you have a bad capacitor if the difference between the measured reading and the actual value is substantially big. 

Keep in mind that capacitors serve different functions in electrical systems and electronics, not to mention they are crucial to accomplish dependability in many applications.

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