How a Multimeter Works In Measuring Resistance?

As of the current scenario, we are available with so many gadgets and instruments that aim to provide an easier lifestyle.

A multimeter is one such tool that comes with a lot of benefits and functions. However, everyone can’t understand how an instrument works, especially while using it for the first time.

In this article, we’ll know about how a multimeter works in measuring resistance. So stay tuned.

Knowing about Multimeter:

As the name suggests, a multimeter is a hand-held device that comes with various (“multi”) measurement functions (“meter”). In simple terms, a multimeter is an electronic instrument that can be used for measuring voltage, current, capacitance, resistance, continuity, and others. Thereby, multimeters are also known as volt-ohm-milliammeter or VOM. It’s a common tool to troubleshoot electronic faults and failures. Overall, it’s an all-round tool for different electronics requirement.

Knowing about Resistance:

Resisting(opposing) the flow of electric current is known as ‘Electrical Resistance.’ It is generally measured in ohms and denoted by Ω(omega). Scientifically, various factors affect a device’s resistance, which includes material, length, and thickness.

What is Ohm’s Law:

Ohm’s Law is a formula used to calculate the relationship between voltage, current, and resistance in an electrical circuit. If you know the values of current and voltage, you can easily calculate any circuit’s resistance. However, a compound instrument like a multimeter will do the job.

If you are a new user of multimeter and not aware of how to use a voltmeter you can checkout our detailed guide here.

Multimeters and Resistance:

An important measurement that can be performed using a multimeter is resistance. It allows you to check the functionality or accuracy of a resistor and also measure resistance. Whether you’re using an analog or digital multimeter, every multimeter uses the same principle to measure any device’s resistance.

The two probes of a multimeter set a voltage and allow current to flow in the circuit. At this time, you can measure the amount of resistance build-up in the device. That’s all the main idea behind resistance measurement using a multimeter.

Components of a Multimeter:

Before discussing how a multimeter works in measuring resistance, it’s important to know about the device. A typical multimeter consists of four major components: a display, a selector dial, connection ports, and two probes.

• The display – A multimeter usually has a seven-segment, multi-digit LCD that shows the readings. Some multimeters feature a backlight display that improves visibility in dark conditions. You’ll also come across multimeters with LED displays that are easier to read.

• Rotary Range Selector Dial – A rotary switch or dial allows you to select the function based on the project requirement. In non-auto-ranging multimeters, this switch also allows you to select measurement values.

• Connection Ports – The sockets where you plug probe leads are known as connection ports. The ports and probe lead both are 4 mm.

• Probes – A multimeter comes with two probes: Black and Red. These leads act as a conductor between the device and the multimeter. One end of the probe has a pointed tip that you touch against the device for measurements. Simultaneously, the other end has a plug that needs to be inserted into a socket.

How to Measure Resistance with an Analogue Multimeter?

An Analog multimeter provides an easier way to measure the resistance of any device or circuit. A key point to note while using an analog multimeter is always “zero” the meter before making any measurement. You can do this by connecting both probes and making a short circuit. Following listed are some simple steps for resistance measurement using an analog multimeter:

Step I: Select the device and turn it off:

You can measure the resistance of any circuit or device. Also, try to find an estimated resistance of the same device/circuit. Before bringing the multimeter into the scene, you must turn-off any equipment attached to the circuit. It’s good for you and your safety. If you don’t a turn-off, you are at high risk of damaging the equipment and the multimeter as well.

Step II: Turn on the multimeter and select resistance measurement:

It’s time to bring your analog multimeter into the scene. Turn the power selector switch to the ‘ON’ position to activate your analog multimeter.

Based on your multimeter’s interface, you need to select the ohms measurement or any symbol representing ohms. This symbol is generally omega, which looks like “Ω.” Some multimeters have a clear “resistance” label included in their interface. Conclusively, whatever naming scheme your multimeter uses, choose the setting that allows you to measure resistance.

Step III: Insert the lead probes into correct sockets:

An analog multimeter usually doesn’t have several ports for probe leads. In this step, you’ve to insert the black and red leads into the appropriate socket. Many multimeters have only two sockets, labeled as positive and negative. Now, insert the black probe into the negative slot and the red probe into the positive slot.

Nowadays, there are multimeters available in the market that feature unique slots for measuring resistance. If you aren’t sure about the appropriate slots, we recommend taking help from the manual provided.

Step IV: Test the analog multimeter by zeroing it:

Before moving to our main task (resistance measurement), it’s essential to test the multimeter to check whether we are getting the correct readings or not. How to do this?

Now, you’ve to touch the pointed tip of both the probe leads together. This will create a short circuit and then take the result to zero ohms. In other words, if your multimeter is working fine, then you should expect a result of infinite ohms. Basically, analog multimeters don’t show the “0 ohms” (no resistance) readings while touching the test leads. However, you’ll see the needle jumping on the opposite side towards the infinity mark. You’ve to repeat this step if the range changes.

Step V: Measure the Resistance:

The main step for which we’ve been waiting for is finally here. Place both the probe leads on the device/wire/circuit that you are aiming to measure. Now, you need to show some alertness and calmness. While touching the probes with the equipment, observe the readings in the analog multimeter. To get precise readings, look at the analog graph and needle scale from different angles. You can compare this reading with the specified resistance rating of the equipment.

How to Measure Resistance with a Digital Multimeter?

When compared with an analog multimeter, a digital multimeter makes resistance measurement more manageable and faster. Since there is no need to zero the meter, you are saving time and avoiding inconvenience. Digital multimeters feature a digital display to show measurement readings; there is also no reverse reading scene.

Step I: Select the device and turn it off:

A digital multimeter allows you to measure the resistance of any object. Any object, means, any wire, circuit, device, or equipment. However, if the component you’re going to measure is connected to any power source, turn the power off. Your equipment should remain disconnected from any existing circuit as the multimeter leads apply a voltage across the equipment ends.

Step II: Insert the probes into correct sockets:

Take out the digital multimeter from your toolkit. Now, you’ve to insert both the test leads into appropriate sockets. The red-colored lead will make its way to the positive input jack, while the black colored lead will be inserted into the negative input jack.

Your multimeter may have a COM socket and a resistance socket (with the “Ω” omega symbol). Insert the black lead into the COM socket and the red lead into the V-marked socket (or Ω symbol). Look at the picture below.

Step III: Set-up your digital multimeter:

Based on the digital multimeter you own, you need to select the required range. If you’re using a meter with a manual range selection switch, then turn the dial to AC/DC volts and choose a range for added accuracy. For example, if your equipment measures “12-volt” on the 20-volt range, it’ll give more decimal place accuracy than the 200-volt range.

On the other hand, if you’re using a meter with an auto-ranging function, turn them to the ‘V’ setting with an AC or DC symbol.

Step IV: Make the measurement:

This is the most important step where you need to measure the resistance of your device. Apply the probes across the item that needs to be measured. Once you touch the probes with the equipment, you’ll see a change in the meter’s display. The figure displayed is the resistance of the object. You can wait for a few seconds and allow the readings to settle down.

Step V: Turn-off the multimeter:

We know that a digital multimeter runs on a battery. Once the resistance measurement is over, you can turn-off the multimeter to save the battery. We also suggest selecting the high voltage range using the function switch. Consequently, if you use the meter again for another measurement, then it won’t cause any damage. Your equipment and multimeter will remain safe even if the range and function chosen are inappropriate.

Some Precautions While Measuring Resistance:

Not only resistance measurement, but you must take some precautions while measuring any quantity with a multimeter. A multimeter is a hand-held device that can be easily damaged or breakdown if not handled properly. Additionally, if you don’t approach accordingly, then you may not receive accurate readings.

• Never measure the resistance of connected components – We suggest measuring the resistance of any equipment that is not connected in a circuit. There’s a basic reason behind approaching this practice. When you measure the resistance of any connected item, the other components around will have some effect. Consequently, you’ll measure some incorrect readings.

• Capacitors should remain discharged – You’ve to ensure that all the capacitors in the circuit are discharged. If they are not, the current flow will take place and affect the measurements. It is also possible that capacitors develop a charge due to the current from the multimeter. Consequently, it may take a while for settled down readings.

• Circuit under test should remain turned off – Sometimes, you may have to calculate any circuit’s resistance instead of a device. In such a scenario, it’s essential to ensure that the circuit isn’t turned on. If you do this, you’ll receive improper or inaccurate readings. Additionally, you may also end up damaging your multimeter. So, be careful.

Conclusion:

An instrument like a multimeter is a must-have tool for every home user and electronics professional user. Over many years, whether analog or digital, multimeters have been gaining immense popularity since then. In this article, we had a comprehensive discussion on “How a Multimeter Works In Measuring Resistance.” Hopefully, you are well aware of multimeters and resistance measurement by now.

Measuring resistance with a multimeter (analog or digital) is pretty simple and straightforward. While performing resistance measurement, you’ll hardly face any problem with analog and digital multimeters. However, while reading the measurements, you may face some difficulty with analog meters. Therefore, best digital multimeters for home use and electronics are becoming more popular.