HOW TO TEST ELECTRICAL COMPONENTS WITH A MULTIMETER
What Is a Multimeter?
A multimeter is a tool used to measure several functions of an electrical component to assess its condition. Multimeters are used to troubleshoot electronics by detecting where connectivity problems may lie within a given electronic, and by diagnosing the type of issue – or at least indicating to the technician what their next step should be.
Among various functions, multimeters are most commonly used to test continuity, resistance, and voltage:
Continuity
A continuity test is performed to determine whether two items are electrically connected, allowing an electric current to flow from one to the other. When testing for continuity, you place the probes of the multimeter on either side of the component. If the resulting reading is at or around ‘0’, the component is continuous. A reading of ‘1’ or ‘open loop’ indicates that the component is non-continuous, and does not allow electricity to flow through it.
Resistance
A resistance test is performed to determine how much current is lost during its journey through an electrical component. Various parts and components have different strengths, so before you test a part, you need to know how much resistance it should have. Always disconnect any device or component from an energy source before testing for resistance. Like when you measure for continuity, a resistance test involves placing the probes of the multimeter on either side of the component to get a reading.
Voltage
A voltage test is performed to assess the force of an electric current. Like when testing resistance, voltage testing requires you to know the expected voltage range beforehand to appropriately set your multimeter and to know whether the reading indicates an issue or not. The testing process for voltage is similar to other multimeter tests, but individual multimeters may come with specific instructions.
Using a Multimeter
Multimeters make it easy to automatically check the condition of various electrical components, but you will need to learn to properly set up and use a multimeter for the most accurate readings. First, determine what type of test you are performing, and select the appropriate setting. If you are checking for resistance, you will need to choose the Ohms setting, whereas you will need to choose either AC or DC if you are measuring voltage.
When using a multimeter, the most important step to remember is to select a voltage or range that will be higher than the expected value of the component you plan to test. Always disconnect any device you plan to test or troubleshoot from its power source before disassembly.
Checking Electrical Components
Electrical devices can malfunction or become damaged in a huge number of places, which is why it can sometimes be difficult to find the source of the problem. With tools like a multimeter, you can test the individual components of a device, helping you to pinpoint the issue, test components before use, perform routine testing and repairs, and more.
Battery
Before replacing components or making major repairs on a device, the first step most technicians take is to test a device’s battery. Using a multimeter to test a battery’s voltage, you can determine whether a battery is fully charged, in need of charge, burnt out, about to burn out, and so on. By testing a battery for its voltage, you can rule out certain electrical issues, keep track of when batteries need replacing, and ensure your devices are being powered properly.
Cables & Wires
Cables and wires should be tested before being used or added to a device, but can also be tested once they have already been installed. Cables are tested for continuity, assessing their ability to channel electrical charge and transport it from one place to another.
Capacitors & Inductors
The first step in testing a capacitor or inductor is to ensure the unit is discharged. Set the multimeter to measure Ohms, and connect the probes to the terminals. If the meter reads ‘open line’, the unit is in good condition. If there is no change, and no reading appears on the meter, the unit is dead.
Diodes
Disconnect the diode from its power supply
and ensure that it is discharged. Set the multimeter to ‘diode test’, and
connect the meter probes to the diode leads. Test, and note the reading. Next,
reverse the test probes and test again, also noting this reading.
If the first reading shows 0.5V – 0.8V (silicon) or 0.2V – 0.3V (germanium), the
diode is in good condition. If the reversed test reads OL (open line), the diode
is confirmed to be in good condition. If the reading shows OL in both
directions, the diode is dead. If the meter shows a reading of around 0.4V in
both directions, the diode is short and needs to be replaced.
Fuse
Connect the probes of the multimeter with the fuse, and set the meter to ‘resistance’ mode. If the reading shows 0, the fuse is in good condition. If the reading shows ‘infinite’, it is an indication of a problem and the fuse may need to be replaced.
LEDs
First, disconnect the LED from its power source. Set the multimeter to ‘diode test’, and connect the probes to the LED terminal. If the LED glows, it is in good condition – any other result shows a defect or lack of charge.
Relays
Set the multimeter to ‘continuity’, then attach the probes of the meter to the coil terminals of the relay. If the multimeter makes a sound or shows any reading of continuity, the coil is in good condition. If the meter shows no change or gives no indication of continuity, the relay is damaged and needs replacing.
Resistors
Set the multimeter to ‘resistance’, then attach the probes of the meter to both ends of the resistor. If the meter reads with an exact value of resistance with a percentage tolerance, the resistor is in good condition. If the meter shows a reading of ‘infinite’, there may be a defect or the resistor may be broken and needs to be replaced.
Switches & Push Buttons
Place the switch or push button in the ON position. Set the multimeter to ‘resistance’, then attach the probes of the meter to both terminals of the switch or push button. This test should produce a reading of ‘0’. Next, push the button or flip the switch to put it into the OFF position, then perform the test again. This test should produce a reading of ‘infinite’.
If both tests produce a reading of 0, or both tests produce a reading of infinite, the switch or button has malfunctioned and needs to be replaced.
Transistors
Using a multimeter, you can test the Base, Collector, and Emitter of a transistor.
Check out this guide for a full description of each of these tests.
Resistor & Burnt Resistors
To check if the Resistor is in good condition or broken, we use a multimeter. For this purpose, take AVO meter (or Digital Multimeter) and select “Resistance” (in AVO meter…Rotate the knob to the “Ω” or Resistance). Now connect both ends of the resistor with the AVO or Digital Multimeter Terminals. If the meter reading shows the exact value of resistance or with a percentage tolerance, it means Resistor in “Good Condition”.
For Example, 1kΩ = 1000Ω with a 5% tolerance will show the reading near about 950Ω to 1050Ω. On the other hand, if meter reading is “Infinite”, it shows the Resistor may be defective or broken and open. So you need to replace it with a new one (exact value).
You can also check the value of a burnt resistor using a digital or analog multimeter by the following three handy methods.
Related Post: How to find The value of Burnt Resistor ( By three handy Methods )
Relay Coils & SSR Relay
To test an SSR (Solid state relay) and electromechanical relay coils by using a multimeter, You will have to follow the detailed and step by step guide about “How to Test a Relay? Checking SSR & Coil Relays“.
Measuring Electrical Quantities Using Multimeter
General Precaution
- Disconnect the power source before checking, servicing, repairing or installing electrical equipment and devices.
- Always, Select the higher value in Digital or analog Multimeter, and then, gradually reduce it to the proper valve.
- Never try to work on electricity without proper guidance and care
- Read all the instructions and cautions and follow them strictly.
- The author will not be liable for any losses, injuries, or damages from the display or use of this information or try any circuit in the wrong format so please! Be careful because it’s all about electricity and electricity is too dangerous
How to Test Electronic Components
While people recommend removing the component from the appliance it is being used on, prior to testing it. Many components already installed on a circuit board can, however, be tested while still on the circuit board. These circuit board components can be tested where they are, capacitors, resistors, transistors and integrated circuits are such components. Obviously, start by looking at the components on the board to see if they are in good condition - a broken component stops the appliance from working or builds up to a bigger problem.
There are three major things to test.
1. Continuity is the first thing to check. This tests if electricity can flow through the component.
2. Resistance is the next thing to test for. Here you are checking to see if there is current loss when electricity is flowing through the component. Ohms are the measurement here and this can become a complicated test. You need to manually set the expected range of loss, while making sure the expected voltage can be handled by the multimeter you are using.
3. Like the test for resistance, checking Voltage and the force of electric pressure requires a multimeter. Here you need to know if it is AC or DC current - a voltmeter can also be used here.
Continuity should be first, as it gives you the required baseline for testing resistance and voltage. Testing diodes can be done without the continuity, as they are one directional - thus “by measuring the resistance in both directions, it is possible to ascertain whether the diode is working, and also which connections are the anode and cathode,” Electronics Notes explains.
If you plan on testing numerous components, Instructables provides a build for a tester that can be used on virtually all non power components - the Component Tester.
How-to-test-electronic-components/
How to Test Electronic Components on Finished Boards
Although testing can involve many complex procedures, particularly with ICs, there are some simple steps a designer can take to ensure their board was fabricated correctly and there are no component defects:
- Visual inspection: Look over the entire board for any signs of damaged components. Also, watch for any ICs with discolored or melted packaging. This may require a magnifying glass or microscope.
- Component power test: Power up the board and use a voltmeter to measure the voltage reaching the components. Sometimes, an apparent component failure is a simple matter of poor power distribution. You might need to look up PCB footprints for your components to ensure you’re checking the right pins.
- Power distribution test: In addition to measuring the power reaching components, you can check the voltage at various points in your power tree with a multimeter. Make sure you measure with respect to the correct ground point to ensure safety and accuracy.
- Bipolar transistor measurements: You can use a voltmeter to measure the built-in voltage of BJTs on the board by connecting the meter to the collector and emitter. This is usually ~100 mV for small transistors.
Points 2 and 3 in the above list are normally checked during in-circuit testing, which can be requested from a manufacturer. It carries some programming costs, so it might be better to do this in-house if you’re only producing a small run or you’re building prototypes. More specialized tests, such as signal integrity tests or logic tests, may require specialized equipment not used by all PCB manufacturers. If you’re scaling from a prototype to full-scale production, keep testing requirements in mind as you work with your manufacturer to start production.
In-circuit testing is known to identify over 95% of defects requiring rework during manufacturing
Use Verified Component Data for Testing
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Electrostatic-Dissipative Workbenches
Static electricity – which is electricity that can jump between objects/surfaces, collect, and produce a static shock – can be highly disruptive when working with electrical components. Static electricity can be both disruptive and dangerous to both electrical components and sensitive electronic devices and may throw off or create false results when taking measurements with a multimeter. To ensure that your results are accurate, and to protect sensitive electronics from sudden static shock, outfit your lab, research center, or manufacturing facility with electrostatic-dissipative workbenches.
Electrostatic-dissipative materials are specifically designed to create a safe, controlled environment in which static electricity can be grounded and neutralized, preventing them from transferring to other objects like sensitive electronics. Electrostatic-dissipative materials act to reduce the risks associated with static electricity in three simple ways.
1. First, these materials are classified as ‘anti-static’, meaning they reduce the occurrence of static electricity, and are semi-resistant to its accumulation.
2. Next, electrostatic-dissipative materials create a pathway through which static energy can travel slowly, and in a controlled manner.
3. Finally, electrostatic-dissipative materials ground the energy, neutralizing it.
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