How to Measure Output Impedance with a Multimeter

Measure Output Impedance with a Multimeter

Wondering how to measure output impedance with a multimeter? This guide will help! Impedance has a great deal to do with the amplifiers. The input and output of the impedance are highly related to the performance of the amplifiers, so measuring the output impedance means measuring the amplifier’s output performance. The value of the output impedance changes with the number of devices linked to the amplifier.

Impedance is the amount of resistance that comes against the voltage in the amplifier. That’s why it is measured in ohms, but we cannot call it resistance because resistance is used for the DC current, and impedance resist the AC current. The amplifier has the AC current, so the resistance there will be called the impedance, which is usually represented by the Z symbol.

Importance of measuring the output impedance

The lower will be the output impedance, the higher will be the amplifier’s efficiency. You might understand the importance of output impedance from this line easily.

It is important to calculate the output impedance because it will let you know what kind of resistive effects the sound signals have to face while passing from the amplifier. So when you calculate the output impedance, you realize that the resistor in the circuit is offering what amount of impedance to the sound signals.

If the value of the impedance is zero, then the music signal does not have to come across with that resistance. No resistance will have any impact on the signals.

Still, if the impedance has some other value than zero, then it means that the output signal will face a lot of resistance by the impedance, and as a result, you will get the lower quality sound signals from your speakers.

Higher impedance values can also ruin the quality of your amplifier and speakers. So it is important to perform a test so that you can get to know if there is an impedance that is causing the trouble in the output signals or if some other factor is responsible for this.

How to measure output impedance with a multimeter?

Using a digital multimeter for measuring electric terms like continuity, voltage, resistance, and impedance will always be the best choice because it is the easiest way of doing that so use the digital multimeter and measure the amount of the output impedance of your amplifier by following the given guidelines.

Measure output impedance with a multimeter (Quick steps) :

  • Turn on the digital multimeter
  • Set the digital multimeter to measure the resistance
  • Set the range of the digital multimeter
  • Cut the power supply to the speaker.
  • Connect the leads of the digital multimeter with the speaker.
  • Take the readings of the impedance.
  • Compare the resulting readings with the lowest impedance readings of the speaker.

Here is a step-by-step procedure below for a better understanding.

Turn on the digital multimeter:

The first step is to turn on the multimeter so that you can start measuring the output impedance by using the digital multimeter.

Set the digital multimeter to measure resistance:

The second step of the measuring procedure is to set the digital multimeter to measure the distance. For this, you have to turn the dial of the digital multimeter towards the resistance or ohms symbol.

Set the range of the multimeter:

Setting the range of the multimeter means that you have to set the specific range of resistance on the multimeter, within which any detected resistance cannot harm the multimeter.

If you have an automatic digital multimeter, you don’t have to do this step, but if there are different ranges on your digital multimeter, you must select a specific range. You can choose any resistance range from 20 ohms to 200 ohms.

Cut the power supply to the speaker:

Now you have to disconnect the speaker from any current supply because when you test the output impedance of the speakers, then make sure that no current is passing from here.

Because if it is getting any current, you will not get the correct readings and measurements on your digital multimeter. Cut down any wires from the speaker that provides current to it.

Connect the leads of the digital multimeter with the speaker:

This is the most important part of this measuring procedure. We know that a digital multimeter has two leads, so you have to connect both of the digital multimeter’s leads with the speaker’s terminals.

Connect the black probe of the multimeter with the negative terminal of the speaker and the red probe of the multimeter with the speaker’s positive terminal. Do not change this setting because this is the actual way of connecting the digital multimeter leads with the speaker to calculate the impedance.

Take the readings of the impedance:

This is the final step of this procedure, where you will get the impedance readings on the digital screen of the multimeter after connecting the leads with their speaker terminals.

You have to note down this reading.

Compare the resulting readings with the minimum impedance readings of the speaker:

You have to see the speaker’s minimum impedance readings, which the company labels on the speaker’s side. After taking the output impedance readings by the multimeter, you have to compare both of the readings.

If the output impedance reading is around 15% less than the speaker’s normal minimum impedance readings, then the results are normal. A higher impedance value can also harm your amplifier and give you bad-quality music signals if there is a huge difference between the readings.

Final verdict:

There are many other methods of measuring the output impedance of the speaker. You can also measure this using an oscillator, but the digital multimeter is the easiest and most famous method of calculating the output impedance.

Suppose you see a huge impedance value coming in the result. In that case, you have to check them by a professional electrician so that your other tools, like a speaker, mic, and amplifier, can stay intact because of this high resistance value.

Frequently Asked Questions

What can I do if I am not finding the nominal impedance value on my speaker?

You can search the nominal impedance value of your speaker by using its model name and searching on the internet. There you will get the exact or around the nominal impedance value you can use in the test.

What can I do to measure the output impedance if I do not have a digital multimeter?

You can also measure the output impedance using impedance meters, impedance analyzers, or LCR meters.

What are the normal impedance ratings of most speakers?

The impedance value for most speakers ranges from 4 ohms to 16 ohms depending upon the quality and size of the speaker.

What if the impedance meter shows the impedance value of the speaker larger than 20 ohms?

The normal impedance value of the speaker ranges typically from 4 ohms to 16 ohms. Any readings above this range are not normal, so your amplifier is not in good condition if the impedance meter shows an impedance value of more than 20 ohms.

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