Transformer is very useful device which is used in both electrical and electronics circuit.In this article we will describe how to test transformer with multimeter.
Checking of transformers can be done in the following 2 types.
1) Transformer voltage testing: Testing of transformers by measuring volts
We had told in the post What is transformer that the job of transformer is to increase or decrease the AC voltage only. This means that if the transformer is correct, after supplying it in the primary coil, the output from the secondary coil must also be found.Therefore, if the transformer is not supplied after supplying the input to the transformer, then the transformer can be considered bad. Voltage testing of transformers can be done with a multimeter or AC voltmeter.
2) Transformer coil testing: Testing of transformers by resistance method
In the post with the transformer, we had said that only the coil is fitted in any transformer. Also any coil can be checked by measuring resistance. Therefore, it is obvious that the whole transformer can be checked by alternating testing of the coil of the transformer. The transformer can be checked by resistance method using DC tester, resistance meter and any type of multimeter. In this method, the transformer is not supplied.
1) Multimeter: Multimeter to transformer testing
In repairing, almost all electrical goods are tested with a multimeter. Therefore, almost all electrical mechanics use multimeters to do transformer testing. Checking the transformer with a multimeter is called a transformer multimeter test. The transformer can be checked with both digital multimeter and analog multimeter type meters. The transformer can be tested by both the volt and resistance method from the multimeter.
2) AC Voltmeter: Testing of transformer with AC voltmeter
Testing of transformers can be done using AC voltmeter by volt method. If you do not have a multimeter, you can test the transformer with a voltmeter. The result of both will be same.
3) Resistance Meter: Testing of transformer with resistance meter.Testing of transformers can be done by resistance meter with resistance meter. If you do not have a multimeter, you can test the transformer with a resistance meter. The result of both will be same.
4) DC tester: testing of transformer with DC tester
A DC tester is a type of electric tester with the help of estimating the resistance between a particular point of any circuit without power flowing. Simply put, a DC tester is used to perform an approximate continuity check. The DC tester consists of a small DC LED bulb. The DC tester's LED bulb will burn in as little light as the resistance value when checking resistance.
Since any transformer has only a coil and the coil can be easily tested by a DC tester. Therefore testing of any transformer can be done easily with DC tester. But one thing should be kept in mind that this tester can only be estimated, the fact that the transformer is defective or correct cannot be said anywhere. This means to say that the DC tester does not get the transformer test report correctly.
How to check transformer primary and secondary: Any transformer has 2 types of coils - primary coil and secondary coil. However, different colored wires are pulled out from both the coil of transformer of good company so that both can be easily identified. But in many transformers, the coil cannot be identified in this way.
If you do not know which coil of transformer is primary and which is secondary, in such a situation, if you supply power to it, then you may have supplied it on the secondary coil itself. In such a situation, the transformer can also be burnt. So below, we are going to tell you some tricks, so that you can easily identify the primary and secondary coil of any transformer.
The coil of the transformer which is thin will be the primary coil and the coil which is thick will be the secondary coil.
The coil which has higher resistance between the two ends will be the primary coil and the coil which has less resistance between the two ends will be the secondary coil.
If any of these topics goes wrong during checking, the transformer will be considered bad.
The primary coil of the transformer is correct.
Secondary coil of transformer is correct.
Primary coils and secondary coils should not be short.
Core and primary coils should not be short.
Do not shortcode the core and secondary coil.
Testing with Voltmeter
First, separate the transformer from all connected circuits after this you should know which coil of the transformer is the primary coil and which coil is the secondary coil. If you do not know this, then first of all, find out this way by the way mentioned above. Now suppose that you have come to know about primary and secondary coils.
After this you should know how many volts your transformer is. This means how much voltage does the transformer provide. Suppose the transformer is of 12 volts. Supply 200-220V AC to the primary coil of the transformer. If you supply less voltage than this, then the output of the transformer will also be low voltage, which will affect the test result.
Now bring your multimeter to a range of 200V AC or more volts. Keep in mind that there is only AC volt in the transformer, so there will be no (+) and (-) in the plug of the multimeter. You can use the multimeter plug upside-down in any way.
Testing of Coil
The voltage of the transformer on the primary coil on which you have supplied is satisfied by checking whether the transformer is getting supply or not. Let's say that the correct voltage is telling here, so let's move forward.Now check the voltage on the secondary coil.
Since your transformer is of 12 volts, if you say about 12 volts on this coil, it means both the primary and secondary coil of the transformer is correct and the transformer is also correct.If 0 volts is indicated on the secondary coil, the transformer is bad.
If the voltage on the secondary coil is less than 12 volts, it means that carbon has formed between the coil and the coil of the transformer. Or the transformer is opened for any reason.
If the voltage on the secondary coil is more than 12 volts, it means that the primary coil of the transformer is short.
Checking shorting of transformer
Above you just checked the transformer coil. If everything is correct till the above mentioned then your transformer will work correctly. But the shorting between primary coil and secondary coil and shorting between both coil and core is yet to be checked. So let's do the transformer shorting test now. Keep in mind that during this checking, it is necessary to supply the transformer. And also the multimeter should be on the range of maximum AC volts.
How to test a transformer with an ohmmeter: The trick we had mentioned above to check the transformer was the trick to check with the voltage method. Now we are going to tell you how to check the transformer by resistance method. Even while testing with this trick, your transformer should not be in contact with any circuit.
Also, keep in mind that while checking with the resistance trick, the transformer should not supply. You can also touch the transformer and its bare wire while checking through the resistance method. Also, by checking the transformer with this method, the multimeter's red and black plugs can be inverted in any way.
First, check the resistance of the primary coil.
If the resistance is approximately 0, then the primary coil is short.
If the resistance is not stated at all, then the primary coil is open and is bad.
If the resistance is too much, then the primary coil has carbon applied.
If the resistor is indicated according to the coil of the transformer, then the primary coil is correct.
Check the secondary coil as the primary coil too.
Testing with Dc meter
It should be noted here that the resistance of both the primary coil and secondary coil is not the same and there is a lot of difference between the two. That is, the resistance of the primary coil will be higher than the resistance of the secondary coil.Checking the transformer coil with a DC tester
Connect both plugs of the DC tester to both wires of the primary coil.
If the tester burns with full light, the primary coil is short.
If the tester does not burn at all, the primary coil is open and is bad.If the tester lights less than its actual light, the primary coil is correct.Secondary coil checking will also be same as primary coil.
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