What Is A Capacitor And How To Test A Capacitor?

What is a capacitor? How to test a capacitor? What are the methods of testing a capacitor? Why is testing a capacitor necessary?

Are some of the questions that always pop up in one’s mind when someone tells that the capacitor is damaged. Capacitors have become a huge part of our lives while being a very small device and it is being heavily used in various power tools like professional chainsaws, corded drills, electric screwdrivers, log splitters, chainsaw mill, tile saw, backpack leaf blowers, etc. make use of them to store energy in a circuit board but being an electronic device are liable to get damaged with time.

To acquire the power of knowledge about a capacitor read on to find out how to test a capacitor? So that the next time when your tools stop working you can easily test for a faulty or malfunctioning capacitor.


What is a capacitor?

A Capacitor is one quiet electrical component that is accustomed to store energy in an electrical charge form. These are utilized in different electrical and electronic circuits to perform different functions. The charging of a capacitor is often done by arranging a capacitor in a lively circuit. Once it’s connected, then the electrical charge will start flowing through the capacitor.

When the first plate of the capacitor doesn’t hold the electrical charge, then it’s released back to the circuit throughout the secondary plate. So this process within the capacitor is understood as charging & discharging. Capacitors are voltage storage devices utilized in electronic circuits, like those found in heating and air-con fan motors and compressors.

Why Test A Capacitor?

Advantages Of Testing A Capacitor.

  • Reduce line current of the system
  • Improves voltage level of the load
  • Reduce system Losses
  • Improves power factor of the source current
  • Reduce load of the alternator
  • Reduce electricity bill

How To Test A Capacitor?

Methods Of Testing A Capacitor

Capacitors are available in 2 main types: electrolytic, which are used with tube and transistor power supplies, and non-electrolytic, which are wont to regulate DC surges. Electrolytic capacitors can fail by discharging an excessive amount of current or by running out of electrolytes and being unable to carry a charge. Non-electrolytic capacitors most frequently fail by leaking their stored charge. There are several ways to check a capacitor to ascertain if it still functions because it should.


Testing A Capacitor With A Simple Voltmeter

Used To Find The Potential Difference Across The Capacitor
how to test a capacitor

The capacitor is first charged with DC voltage which is less than the capacitor rating. The polarity is important here. The longer lead (anode) of the capacitor to be connected to a positive voltage and the shorter lead (cathode) is connected to the ground or negative terminal of voltage. This method is used to find the potential difference across the capacitor as each and every capacitor comes with a maximum voltage capacity which can be used to test the malfunctioning of a capacitor. Moreover, Only the initial reading on the Multimeter must be taken into account as the value will slowly fall down.

Steps To Test A Capacitor With Simple Voltmeter

  • Remove the capacitor from the board OR circuit and properly discharge it. If you would like, you’ll remove just one lead from the circuit.
  • Look for the voltage rating on the capacitor. it’ll be usually mentioned as 16V, 25V, 50V etc. this is often the utmost voltage which the capacitor can tolerate.
  • Now, connect the leads of the capacitor to an influence supply or A battery but the voltage should be but the utmost rating. for instance , on a capacitor with maximum voltage rating as 16V, you’ll use a 9V battery.
  • Charge the capacitor for a brief period, say 4 – 5 seconds and disconnect the facility supply.
  • Set the Digital Multimeter to DC Voltmeter settings and measure the voltage across the capacitor. Connect the right terminals of the voltmeter and capacitor.
  • The initial voltage reading on the Multimeter should be on the brink of the supplied voltage during a good capacitor. If the difference is large, then the capacitor may be a faulty one.

Testing a Capacitor using Multimeter with Capacitance Setting

Easiest, Quickest And Accurate Method of Testing A Capacitor
How To test a capacitor?

If you’ve got a capacitance meter on your multimeter. All you’ve got to try to do is read the capacitance that’s on the outside of the capacitor and take the multimeter probes and place them on the leads of the capacitor.

Polarity doesn’t matter. this is often an equivalent you ought to read a worth near the capacitance rating of the capacitor. thanks to tolerance and therefore the incontrovertible fact that (specifically, electrolytic capacitors) may dry up, you’ll read a touch less in value than the capacitance of the rating. this is often fine. If it’s a touch lower, it’s still an honest capacitor.

Steps To Test A Capacitor Using Multimeter With Capacitance Setting

  • If the capacitor ratings are visible on its body, make a note of it. Usually, the capacitance in Farads (often micro Farads) is printed on the body alongside the voltage ratings.
  • In the Digital Multimeter, set the knob to capacitance settings.
  • Connect the multimeter probes to the terminals of the capacitor, just in case of a polarized capacitor, connect the red probe with the positive terminal of the capacitor (generally, the longer lead) and therefore the black probe to the negative terminal. just in case of non – polarized capacitor, connect it either way as they are doing not have polarity.
  • check the readings on the Digital Multimeter. If the multimeter readings are closer to the particular values (mentioned on the capacitor), then the capacitor are often considered as an honest capacitor.
  • If the difference between the particular value and therefore the measured reading is significantly large (or sometimes zero), then you ought to replace the capacitor because it may be a dead one.
  • However, if you read a significantly lower capacitance or none in the least, this is often a sure sign that the capacitor is flawed and wishes to get replaced. Checking the capacitance of a capacitor may be a great test for determining whether a capacitor is sweet or not.

Testing A Capacitor Using Multimeter Without Capacitance Setting

Can Be Accomplished With Low end And Cheap Multimeters
How To Test A Capacitor?

There are various low end and cheap multimeters that don’t come with the capacitance setting or capacitance meter but can be easily brought in use to check the capacitor. This method of testing the capacitor might not be accurate but can differentiate between a good and bad capacitors. This method also doesn’t give the capacitance of the capacitor.

Steps To Test A Capacitor Using Multimeter Without Capacitance Setting

  • Remove the capacitor from the circuit or board and confirm it’s completely discharged.
  • Set the Multimeter to live resistance i.e. set the knob to Ohm or Resistance Settings. If there are multiple ranges of resistance measurement, select a better range (often 20 KΩ to 200 KΩ).
  • Connect the multimeter probes to the leads of the capacitor (red to positive and black to negative just in case of polarized capacitors).
  • The Digital Multimeter will show a reading of resistance on the display and shortly will display the resistance of an circuit (infinity). write the reading that was displayed for that short period.
  • Disconnect the capacitor from the multimeter and repeat the test several times.
  • Every attempt of the test should show similar result on the display for an honest capacitor.
  • If there’s no change within the resistance within the further tests, the capacitor is dead.

Testing A Capacitor Using Analog Multimeter (AVO Meter)

Using The Ohmmeter Functionality
How To Test A Capacitor

Another way of testing the capacitor is by using the analog multimeter that shows the measure of various parameters like Current (A), Voltage (V), and Resistance (Ohm). But to measure the capacitance of the capacitor the functionality of the Ohmmeter is used. This method provides an approx. value of the capacitor’s goodwill thus helping us understand whether it is working properly or not. Furthermore, This test can be applied to both through-hole and surface mount capacitors.

Steps To Test A Capacitor Using Analog Multimeter

  • As usual, disconnect the capacitor and discharge it. you’ll discharge a capacitor just by shorting the leads (very dangerous – be careful) but a simple way is to use a load sort of a high wattage resistor or an LED.
  • Put the Analog Multimeter in Ohmmeter position and if there are multiple ranges, choose a better range.
  • Connect the leads of the capacitor to the multimeter probes and observe the readings on the multimeter.
  • For an honest capacitor, the resistance are going to be low within the beginning and can gradually increase.
  • If the resistance is low in the least times, the capacitor may be a Shorted Capacitor and that we need to replace it.
  • If there’s no movement of the needle or the resistance always shows a better value, the capacitor is an Open Capacitor.

Testing A Capacitor By Measuring The Time Constant

Can Only Be Applied If The Capacitance Is Known.
How To Test A Capacitor?

This method makes use of Time and Resistance, where after you have acquired the values of time and resistance the capacitance must be measured and it should be compared with the value printed on the Capacitor. If they are similar or nearly equal, then the Capacitor can be considered as operational. On the contrary, if the difference is significantly large; then the Capacitor should be replaced as it is a dead one.

Time Constant of a Capacitor is that the time taken by a Capacitor to charge to 63.2% of the applied voltage when charged through a known resistor. If C is Capacitance, R may be a known Resistor, then Time Constant TC (or Greek alphabet Tau – τ) is given by τ = RxC.

Steps To Test A Capacitor By Measuring The Time Constant

  • First, confirm that the capacitor is disconnected from the board and is correctly discharged.
  • Connect a known resistor (typically a ten KΩ Resistor) serial with the capacitor.
  • Complete the circuit by connecting an influence supply of known voltage.
  • Turn on the facility supply and measure the time taken for the capacitor to charge to 63.2% of the availability voltage. For example, if the availability voltage is 12V, then 63.2% of this is often around 7.6V.
  • From this point and Resistance, measure the Capacitance and compare it with the worth printed on the capacitor.
  • If they’re similar or nearly equal, the capacitor is functioning properly. If the difference is large , we’d like to exchange the capacitor.

Testing A Capacitor Using Continuity Test

Shows Whether It Is Short, Opened Or Good
How To Test A Capacitor

The Continuity test is another method by which you can easily check whether the capacitor is short, opened or good, or malfunctioning. This method is one o the simplest method to know whether the working of the capacitor.

  • Remove the suspicious capacitor from its circuit.
  • Discharge it employing a resistor.
  • Set the multimeter in continuity mode.
  • Place the multimeter’s red probe on Anode and black (common) probe on Cathode of the capacitor.
  • If the multimeter show sign of continuity (beep or LED) then it stops (shows OL). It means the capacitor is sweet .
  • If the capacitor doesn’t show any sign of continuity, the capacitor is open.
  • If the multimeter beeps continuously, the capacitor is brief and wishes a replacement.

Testing A Capacitor Using Resistance Test

A Multimeter Can Be Used For Testing The Resistance
How To Test A Capacitor?

The resistance can also be another method by which you can easily test a capacitor. To perform this you can make use of an analog multimeter or a digital multimeter but the process of testing will be same or both. This method can also provide a great amount of accurate results about the functioning of the capacitor.

  • Remove the capacitor from its circuit and discharge the capacitor employing a resistor.
  • Set the multimeter knob in high resistance mode(above 10kohm).
  • Place the red probe on Anode & black probe on Cathode terminal of the capacitor.
  • The resistance reading should start from some point within the middle & start increasing all the values to infinite. It shows the capacitor is working fine.
  • If the capacitor shows high resistance even after discharge, the capacitor is open.
  • If the capacitor show 0 or very low resistance, it’s short.
  • The reason for increasing resistance is that originally , the capacitor was charging from the multimeter. So it allows the present to flow through(in which case the ohmmeter measures a resistance).
  • When the capacitor got fully charged, it didn’t allow anymore current. thanks to which, it appears as an open path (infinite resistance)
how to test a capacitor

Not Recommended for everybody but professionals only. Please take care to try to do this practice because it is dangerous. Confirm that you simply are knowledgeable engineer / electrician (you really know that what are you doing or check the warnings before applying this method) and there are not any other options to see the capacitor because serious damages may occur during this practice) as capacitors are known to store energy in an electrical charge form.

If you’re sure, go ahead. For better safety, use 24V DC rather than 230V AC. just in case of the absence of the specified DC 24V system, you’ll use 220-224V AC, but you’ve got to form a serial of resistors (say 1kΩ~10kΩ, 5~50Watts) to attach between the capacitor and 230V AC supply. So that, it’ll reduce the charging and discharging current. Here is that the step-by-step tutorial that how may you check a capacitor by this method.

Steps To Test A Capacitor By Shorting The Leads

  • The capacitor under test must be disconnected from its circuit and must be properly discharged.
  • Connect the leads of the capacitor to the availability terminal. For 230V AC, only non – polarized capacitors must be used. For 24V DC, both polarized and non – polarized capacitors are often used but with proper connection for polarized capacitors.
  • Short the terminals of the capacitor employing a metal contact. Make sure, you’re insulated properly.
  • The spark from the capacitor is often wont to determine the condition of the capacitor. If the spark is large and powerful, then the capacitor is in fitness.
  • If the spark is little and weak, you would like to exchange the capacitor.

Final Verdict

The Conclusion

From providing flexible filter options to protecting sensitive microchips from noise to limiting a voltage spike to power storage, decoupling, and more importantly, keeping a continuous power supply, there are different uses for capacitors during a circuit. Capacitors can get damaged thanks to aging, heat, high voltage, humidity, chemical contamination, and moisture. As failing capacitors are one of the common reasons for electrical and electronic malfunctions, as a business owner, you would like to catch a failing capacitor in time by testing it with various methods of your wish as shown above.

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