Best Power Supply Tester

One of the problems that is least seen today in the world of custom PCs is that of home repairs and tests, since as a rule the quality level of the components is very high. Of the components that most often fail we have motherboards , graphics cards and power supplies , where we will focus on the latter to learn how we can know and test its operation.

How to test a power source with a digital tester?

The most important thing when measuring a pc source is to know how to do it and with what tools.

Although, there are two types of tester , one much simpler than the other, to use either of the two we must know the voltages handled by the power supply of our pc.

But before that, we must also be clear that voltage is a physical magnitude that, in an electrical circuit, drives electrons along a conductor. That is, it conducts electrical energy with greater or lesser power.

It is important that before continuing to know a little the basic principles of electricity before continuing with the post. But if you don’t want to read it, it’s not essential either. since here we explain step by step how to measure the source.

1. Safety Rules for Measuring or Testing a Source

Another great recommendation is that they make sure they are not barefoot when doing the test, much less wet. or in an environment that favors electric shock. and THEY MUST NEVER OPEN THE POWER SOURCE , whether it is on or not, since there is usually electricity stored in it.

If they do, they run at their own risk of electric shock, remember that it goes to the 220v alternating current of their homes.

2. The Tester or Digital Multimeter: what it is and what it is for

The Digital Multimeter or Tester is used to make measurements of voltage, current, resistance, etc. from our pc.

The Multimeter or Tester has a knob that allows you to select values ​​between 5 zones:

  • ACV: alternating voltage
  • DCV: direct voltage
  • DCA: direct current
  • Resistance (symbol)
  • OFF: off

3. How a Multimeter or Pc Tester Works

In each area of ​​the digital tester or multimeter there will be different scales. Observe the area that will allow you to measure direct voltage (DCV).

In it you will find the following scale of values: 1000V, 200V, 20V, 2000mV and 200mV, these are the maximum values ​​that you can measure.

Depending on the voltage to be measured, you must place the selection key on the
corresponding value .

If, for example, you have to measure a common 9V battery, we must choose a scale that is larger and that is as close as possible to this value, the selector switch of the tester must be positioned in the DCV zone at the value 20V.

In the following image, you can see that there are three pins to connect the measuring tips:

  • Plug for current up to 10A: the red tip is connected to it, only to measure
    current up to 10A . This plug will never be used.
  •  V, Ω plug. The red tip is connected here, when you want to measure voltage,
    resistance or current.
  • Earth plug: the black tip is connected to it.

“If we do not know the value to be measured, in order not to run the risk of burning the tester, we must choose the maximum scale and carry out the measurement. Then, if this scale is large or does not allow us to obtain the desired precision, we will choose a smaller one and so on.

In the following table you can see the different reading values ​​of the tester depending on the scale that is selected, to measure a continuous voltage of 12.23V “

The closer the scale is selected to the value to be measured, the more accurate the measurement will be.

The 1 that is read on the 2000mV scale indicates that it was out of range, that is, the value that it would be measuring is greater than the maximum allowed on that scale. You should be very careful not to exceed the maximum value, otherwise you run the risk of ruining the instrument.

4. How to Measure Voltage with the Multimeter or Tester

To perform the measurement, you must subject the tester to the same voltage that you want to measure, then the tester must be in parallel with the element (resistance, battery, etc.).

Steps for the measurement with the Multimeter:

  1.  Place the tips: the black one on the earth plug and the red one on the voltage (V).  
  2.  Select the DCV (direct voltage) or ACV (alternating voltage) zone and the scale with the selector knob. 
  3. Connect the tips in parallel with the element. At this point you must take into account whether the voltage to be measured is direct or alternating.

If it is continuous, you must connect the red tip to the positive terminal and the black tip to the negative, otherwise you will get a negative value.

This negative value indicates that the real poles (+ and -) are opposite to the position of the tips.

The analog testers , have a needle to indicate the measurement, if the tips are invested in these tester, the needle tends to rotate to the opposite side to the clockwise, ruining the instrument.

In the case of alternating voltage, it does not matter how the tips are positioned since their effective value is measured.

5. How to measure resistance and continuity

To measure resistance (resistors) or continuity (circuit), you must place the selector switch of the tester in the ohms position and on the corresponding scale. The tips of the tester are placed at the ends of the element whose resistance value is to be known or, in the case of continuity, in order to determine whether it has it or not.

The graph shows how a resistance is measured.

“The energy delivered by a power supply in one second is called power.”

Power is represented by the symbol P and its unit of measurement is the watt or watt. Analytically, electrical power is the product of voltage and current. This is: P = I x V

As seen above, in the household outlet it will have an alternating voltage of 220 V. One of the cables is called “neutral”, it has no voltage and allows the return of current to your electricity supplier.

The other cable is called “live”, since it is the voltage provider.

“You must be very careful with the live wire, because if you touch it you run the risk of electrocution.”

The ground discharge The ground line is composed of a javelin buried in the ground, to which a cable is connected that will be used for the ground discharge.

The ground discharge has the function of protecting our lives.

Generally, the vast majority of electrical appliances have a third prong in the plug that is connected to the appliance’s housing. If for any reason there is voltage in the case, the generated current will flow directly to the ground and not through your body when you touch the equipment.

6. Norms and electrical safety rules when using the Tester

Any knowledge of an electrical system is incomplete if the physical dangers that it can pose to people and facilities are not known.
Electrical energy is very useful and easy to manipulate, but it is also dangerous and potentially lethal. Most electrical accidents occur due to recklessness or ignorance of basic safety rules.

Never work on energized devices, or assume a priori that they are disconnected. If you need to work on an energized circuit, always use tools with insulated handles, as well as protective equipment appropriate to the electrical environment in which you are working.

  • The footwear that you wear must guarantee that your feet are perfectly isolated from the floor.
  • Do not work in wet areas or while yourself or your clothes are wet.
  • Moisture reduces the resistance of the skin and favors the circulation of current.

Now that we have the theory, let’s get down to business!

Measurement of an Atx source

Very well, we have arrived at the part that interests us! How to measure a power supply with a tester or digital multimeter ! To do this there are two ways to test a power source:

The first and the easiest is to get a tester like the one in the image, and connect the source cables as in the photo, and check the voltage values ​​of a source.

7. Steps for Measurement with a Digital Multimeter

1.Place the power supply on the table to measure it

2. Place the clip by bridging the GREEN connector in the image with ANY BLACK as shown in the image

3. Connect the source to the current in your home, with great care and try NOT TO HAVE THE SOURCE OPEN for your safety, take all the necessary precautions not to link a 220v kick.

When connecting automatically the source will turn on, at that moment we can measure one by one the voltage values ​​that each pin of the board throws, it would be like this.

4. Place the Tester in 20v direct current. The red meter will be placed on each colored wire and the black one that is ground always on any black.

5. If you do not know the values ​​that each colored wire of the connector should show, visit this entry: Colors and voltages of a source.

Thank you very much for following the post! I hope you have learned how to measure the voltages of your power supply with a digital tester, in order to know if they should change it or not.

Power supplies are an extremely complex component

And they are so from an electronic point of view, since their well-known function includes regulating the voltage in the most precise way possible, wasting the least energy in the form of heat that it allows and above all with the greatest stability in voltages and amps. that I manage to achieve.

Although, as we have said previously, they have improved the average quality a lot, reaching in the cases of extreme sources to last decades in many cases (even covered by warranty) they are not components that have a very low failure rate, since they are increasingly demands more from the rest of the components. As you know, we always recommend investing a significant amount of money from each budget in this component, which will avoid problems in the rest of the components in most cases.

But if a source fails, it is best to do a brief manual or automatic seft-test and thus be able to detect where the problem comes from. For this we will have to get a good multimeter or even in the most delicate cases with a complete station. In most cases, a medium multimeter will be more than enough, since by detecting a minimum voltage variation we can be satisfied with the test.

Tester vs multimeter

There are several ways to test the stability of the power supply. The most comfortable one is undoubtedly an exclusive tester for sources, where it acts as a multimeter, except that in many cases it is not as precise and updates the values ​​less frequently than its «rival» gets.


LEAGY 20/24 4/6/8 Pin 1.8 “LCD Computer PC Power Supply Tester for SATA, IDE, HDD, ATX, ITX, BYI connectors
Another problem with this type of tester is that it does not allow testing 8-pin cables for graphics cards, that is, the usual 8-pin PCIe, although it does with the 6-pin one. Recall that the EPS of 12 volts and 8 pins is not the same as that of PCIe 8 pins. Therefore, the multimeter option is more complete, so we are going to know the simple steps we need to be able to measure the voltage.

In the first place, we must have the source outside the PC , for simple safety and to rule out power derivations to the tower or possible short circuits with any component. Obviously we will have to place it on a surface that does not transmit current, not even static electricity. Once this is done and with the rear switch of the same in circulation and not in flow (“off” so that we understand each other), we proceed to bridge pins 15 and 16 such that:


With any cable or clip we can achieve it, as long as it transmits the clear current. They also sell an anchor that comes prefabricated, so you just have to reach out and plug in.

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