On this tutorial, we are going to see methods to check a Capacitor and discover out whether or not the capacitor is working correctly or it’s a faulty one. A Capacitor is an Electronics/Electrical part that shops vitality within the type of Electrical Cost. Capacitors are sometimes utilized in electronics circuit boards or few electrical home equipment and carry out a wide range of features.
Why do we have to Take a look at a Capacitor?
When a capacitor is positioned in an lively circuit (a circuit with lively present flowing), cost begins to construct up within the capacitor (on one in every of its plate) and as soon as the plate of the capacitor can now not settle for any extra cost, this implies the capacitor is totally charged.
Now, if the circuit calls for this cost (like a bypass capacitor, for instance), the capacitor releases the cost again in to the circuit and it continues till the cost is totally launched or the circuit stops demanding. These motion are known as as Charging and Discharging of Capacitor.
Principally, capacitors will be categorised in to Electrolytic and Non – Electrolytic Capacitors. Like all electrical and electronics elements, a capacitor can also be delicate to spikes and such voltage swings can harm the capacitors completely.
Electrolytic Capacitor typically fail because of discharging extra present in a brief time frame or can not maintain cost because of drying out over time. Non – Electrolytic Capacitors then again fail because of leakages.
There are totally different strategies to check whether or not a Capacitor is functioning correctly or not. Allow us to see a number of the strategies to check a capacitor.
NOTE: Among the strategies talked about right here will not be one of the best methods to check a capacitor. However we included these strategies simply to specify the chances. Be very cautious.
The best way to Discharge a Capacitor?
Earlier than continuing additional and taking a look at totally different strategies of testing a capacitor, allow us to perceive methods to correctly discharge a capacitor. This is essential as a result of capacitors can maintain the cost even when the ability provide is disconnected. If the capacitor is just not discharged correctly and when you accidently contact the leads of the capacitor, it should discharge by way of your physique and trigger an electrical shock.
There are a few methods in which you’ll be able to discharge a capacitor. There will probably be a devoted tutorial on methods to discharge a capacitor however in the meanwhile, allow us to undergo each these strategies very briefly.
Utilizing a Screwdriver
WARNING: This technique is just not most well-liked (particularly in case you are newbie) as there will probably be sparks generated whereas discharging, which could trigger burns or different harm. Use this technique as a final resort.
If the capacitor is within the circuit (on the PCB), then correctly de-solder it and ensure to not contact the terminals of the capacitor. Now, take an insulated screwdriver (with an extended deal with) and maintain it in a single hand. Take the capacitor within the different hand and contact the steel a part of the screwdriver to each the terminals of the capacitor.
You will note sparks and listen to some crackling sound as a sign of electrical discharge. Repeat a few time to be sure that the capacitor is totally discharge.
Utilizing a Discharge Resistor (Bleeder Resistor)
Now, we are going to see a secure approach to discharge the capacitor. This technique is usually utilized in energy provides and different related circuits the place a Resistor, often called a Bleeder Resistor, is positioned in parallel to the output capacitor in order that when the ability is turned off, the remaining cost within the capacitor is discharged by way of this resistor.
Take a big worth resistor (normally, few kilo Ohms) with a excessive energy score (like 5W) and join it throughout the terminals of the capacitor. As an alternative of immediately connecting, you can also make use of wires with crocodile clips on each the ends. The capacitor will slowly discharge and you may monitor the voltage throughout the terminals of the capacitor with a multimeter.
There may be a straightforward to make use of “Capacitor Security Discharge Calculator” from Digi-Key. Use this instrument as a place to begin.
For instance, assume we’ve got a 1000µF Capacitor rated for 50V and we need to discharge this capacitor all the way down to 1V. Utilizing a 1KΩ Resistor, it should take nearly 4 seconds to discharge the capacitor. Additionally, the ability score of the resistor must be a minimum of 2.5W.
NOTE: Excessive Energy Rated Resistors are normally costly when in comparison with regular resistors (1/4 Watt or 1/2 Watt).
Technique 1 Checking a Capacitor utilizing Multimeter with Capacitance Setting
This is likely one of the best, quickest and correct approach to check a capacitor. For this, we want a Digital Multimeter with Capacitance Meter function. A lot of the mid and excessive finish Digital Multimeters embody this performance.
The capacitance meter on the digital multimeters typically show the capacitance of the Capacitor however few meters show different parameters like ESR, leakage, and many others.
- In an effort to check a capacitor utilizing Digital Multimeter with Capacitance Meter, the next steps will be adopted.
- Disconnect the Capacitor from the circuit board and discharge it utterly.
- If the capacitor scores are seen on its physique, make an observation of it. Normally, the capacitance in Farads (typically micro Farads) is printed on the physique together with the voltage scores.
- Within the Digital Multimeter, set the knob for capacitance measurement.
- Join the multimeter probes to the terminals of the capacitor. In case of a polarized capacitor, join the pink probe to the optimistic terminal of the capacitor (typically, the longer lead) and the black probe to the damaging terminal (normally, there will probably be a marking on the facet). In case of non – polarized capacitor, join it both method as they don’t have polarity.
- Now, verify the readings on the Digital Multimeter. If the multimeter readings are nearer to the precise values (talked about on the capacitor), then the capacitor will be thought-about as a superb capacitor.
- If the distinction between the precise worth and the measured studying is considerably massive (or typically zero), then you must change the capacitor as it’s a useless one.
Utilizing this technique, capacitors starting from few nano Farads to few lots of of micro Farads of Capacitances will be measured.
Technique 2 Checking a Capacitor utilizing Multimeter with out Capacitance Setting
A lot of the low finish and low cost Digital Multimeters don’t embody Capacitance Meter or Capacitance Settings. Even with these Multimeters, we will check a Capacitor.
- Take away the Capacitor from the circuit or board and ensure it’s utterly discharged.
- Set the Multimeter to measure resistance i.e., set the knob to Ohm or Resistance Settings. If there are a number of ranges of resistance measurement (on a guide multimeter), choose a better vary (typically 20 KΩ to 200 KΩ).
- Join the multimeter probes to the leads of the capacitor (pink to optimistic and black to damaging in case of polarized capacitors).
- The Digital Multimeter will present a studying of resistance on the show and shortly it should show the resistance of an open circuit (infinity). Be aware down the studying that was displayed for that quick interval.
- Disconnect the capacitor from the multimeter and repeat the check a number of occasions.
- Each try of the check ought to present related outcome on the show for a superb capacitor.
- If there isn’t a change within the resistance within the additional assessments, the capacitor is useless.
This technique of testing the capacitor may not be correct however can differentiate between a superb and dangerous capacitors. This technique additionally doesn’t give the capacitance of the capacitor.
Technique 3 Testing a Capacitor by measuring the Time Fixed
This technique is relevant provided that the capacitance worth is thought and if we need to check whether or not a capacitor is nice or useless. On this technique, we measure the Time Fixed of the Capacitor and derive the capacitance from the measured time. If the measured capacitance and the precise capacitance are related, then the capacitor is an effective one.
NOTE: An oscilloscope will probably be a greater instrument for this technique than a multimeter.
Time Fixed of a Capacitor is the time taken by a Capacitor to cost to 63.2% of the utilized voltage when charged by way of a identified resistor. If C is Capacitance, R is a identified Resistor, then Time Fixed TC (or Greek Alphabet Tau – τ) is given by τ = RC.
- First, be sure that the capacitor is disconnected from the board and is correctly discharged.
- Join a identified resistor (usually a ten KΩ Resistor) in collection with the capacitor.
- Full the circuit by connecting an influence provide of identified voltage.
- Activate the ability provide and measure the time taken for the capacitor to cost to 63.2% of the provision voltage. For instance, if the provision voltage is 12V, then 63.2% of that is round 7.6V.
- From this Time and Resistance, measure the Capacitance and evaluate it with the worth printed on the capacitor.
- If they’re related or almost equal, the capacitor is functioning correctly. If the distinction is big, we have to change the capacitor.
The discharge time may also be calculated. On this case, the time take by the capacitor to discharge to 36.8% of the height voltage will be measured.
Technique 4 Take a look at a Capacitor with a easy Voltmeter
All capacitors are rated with a most voltage that they are often utilized with. For this technique of testing a capacitor, we are going to use the voltage score of a capacitor.
- Take away the capacitor from the board or circuit and correctly discharge it. If you’d like, you possibly can take away just one lead from the circuit.
- Search for the voltage score on the capacitor. It is going to be normally talked about as 16V, 25V, 50V and many others. That is the utmost voltage which the capacitor can tolerate.
- Now, join the leads of the capacitor to an influence provide or a battery however the voltage must be lower than the utmost score. For instance, on a capacitor with most voltage score as 16V, you should utilize a 9V battery.
- When you have a bench energy provide, then you possibly can set a voltage which is lower than the rated voltage of the capacitor.
- Cost the capacitor for a brief interval, say 4 – 5 seconds and disconnect the ability provide.
- Set the Digital Multimeter to DC Voltmeter settings and measure the voltage throughout the capacitor. Join the right terminals of the voltmeter and capacitor.
- The preliminary voltage studying on the Multimeter must be near the equipped voltage in a superb capacitor. If the distinction is massive, then the capacitor is a defective one.
Solely the preliminary studying on the Multimeter should be taken in to account as the worth will slowly fall down. That is regular.
Analog Multimeters, like Digital Multimeters, can measure totally different portions like Present (A), Voltage (V) and Resistance (O). In an effort to Take a look at a Capacitor utilizing Analog Multimeter, we’re going to use its Ohmmeter performance.
- As regular, disconnect the capacitor and discharge it. You’ll be able to discharge a capacitor simply by shorting the leads (very harmful – watch out) however a straightforward method is to make use of a load like a excessive wattage resistor or an LED.
- Put the Analog Multimeter in Ohmmeter place and if there are a number of ranges, select a better vary.
- Join the leads of the capacitor to the multimeter probes and observe the readings on the multimeter.
- For a superb capacitor, the resistance will probably be low at first and can steadily improve.
- If the resistance is low always, the capacitor is a Shorted Capacitor and we’ve got to switch it.
- If there isn’t a motion of the needle or the resistance at all times reveals a better worth, the capacitor is an Open Capacitor.
This check will be utilized to each by way of gap and floor mount capacitors.
Technique 6 Shorting the Leads of Capacitor (Conventional Technique – just for Professionals)
The strategy described right here is likely one of the oldest strategies to check a capacitor and verify whether or not it’s a good one or a foul one.
Warning: This technique could be very harmful and it’s for Professionals solely. It should be used as a final choice to check the capacitor.
Security: The strategy is described with respect to 230V AC Provide. However for security causes, a 24V DC provide can be utilized. Even with 230V AC, we have to use a collection resistor (excessive wattage rated) to restrict the present.
- The capacitor beneath check should be disconnected from its circuit and should be correctly discharged.
- Join the leads of the capacitor to the provision terminal. For 230V AC, solely non – polarized capacitors should be used. For 24V DC, each polarized and non – polarized capacitors can be utilized however with correct connection for polarized capacitors.
- Swap on the ability provide for a really quick period (usually 1 second to five seconds) after which change it off. Disconnect the capacitor leads from the ability provide.
- Brief the terminals of the capacitor utilizing a steel contact. Be certain that, you’re insulated correctly.
- The spark from the capacitor can be utilized to find out the situation of the capacitor. If the spark is massive and powerful, then the capacitor is in good situation.
- If the spark is small and weak, you might want to change the capacitor.
This technique can be utilized for capacitors with smaller capacitances. This technique can solely decide if the capacitor can maintain cost or not.
A whole newbie’s information on alternative ways to check a capacitor. Discover ways to check a capacitor, methods to correctly discharge a capacitor earlier than testing, what strategies are secure to make use of by rookies.