How to Use LCR Meter?

In different laboratories and industries where it’s important to determine whether electronic components are suitable or not, LCR meters are widely used. How to Use LCR Meter?

These are electrical devices that allow us to measure the inductance, capacitance, and resistance of an electronic component. There are a variety of LCR meters on the market.

While the more primitive ones operate internally and display the measurements on the digital display, the more advanced options out there will provide you a more accurate measurement.

These modern LCR meters can provide you the Q factor of inductive components as well as the equivalent series resistance. This is why it’s important to know how to use LCR meter. However, we must know more about how it operates before that.

How Does an LCR Meter Operate?

The operation is fairly complex, but we’ll try to simplify it as much as possible. Basically, the electronic component that you want to measure is known as the device under test or DUT. AC voltage is passed through this component at first.

In this state, the best LCR meter measures the voltage of the current that’s being passed through the device. The meter automatically determines a ratio between the voltages at the two ends of the device.

From the ratio of the voltages, the device measures the impedance. Other than this, the phase angle between the current and the voltage is also taken into account. However, this is measured through more advanced instruments.

These two factors merge together to provide accurate readings on the inductance, capacitance, and resistance of the DUT.

Importance of an LCR Meter

You might be thinking about why you need a best LCR meter. The most necessity of an LCR meter appears when you need to measure the purity of any capacitor or similar electronic component.

An ideal capacitor is a capacitor that offers no resistance or inductance, but it’s not possible to get an ideal capacitor, as they don’t exist in real life.

These LCR meters will allow you to understand how much inductance and resistance a specific electronic device has. The more capacitance a capacitor has, the better quality it boasts. In this way, you can determine the quality of a capacitor accurately.

How to Use LCR Meter?

LCR meters are fairly easy to use, but there are certain things that you need to maintain while using them. The first thing that you need to ensure is that you have the proper settings.

If you have improper settings, the measurements will be affected heavily. This will yield inaccurate results. In this article, you’ll find tips on how you can find the right settings for you.

These are the steps that you need to follow to use an LCR meter properly:

Measurement Frequency

Measurement Frequency in LCR Meter

The component you’ll be testing will decide the measurement frequency of choice, as reactance is a function of frequency. If you measure capacitors, you need to work with larger values, as these are used in filtering applications largely.

On the other hand, if you’re working with smaller capacitors, you need to test them at a frequency of 1KHz, as they tend to be at high frequencies.

The same goes for inductors. If you’re testing small inductors that are below 1mH, then you should test them at a frequency of 1KHz or higher. Then again, large inductors need to be tested near the line frequency.

Measurement Level

The measurement level will largely depend on the component as well as the test conditions. Temperature is surely a great factor here, but the readings will depend mostly on the voltage level that’s applied across the component.

Equivalent Circuit Type

Resistances can be measured in two ways. The equivalent resistances found in the components are either in series or in parallel.

If the reactance is considerably large, measuring with the parallel model is a better option. This is because the series model becomes negligible in this case.

Inversely, if you measure a small reactance, then going for a series model is the right choice, and the parallel one becomes negligible.

It’s the exact opposite for inductors. For large inductors, you need to stick to a parallel circuit, and for small inductors, go for the series circuit model.

D & Q

D is the dissipation factor, and it denotes the impedance divided by the reactance. Q is the quality factor, and it’s the inverse of D. A component is purer when the value of D is smaller.

Capacitance accuracy discrepancies

You can get inaccurate readings of capacitance if you choose the wrong settings. For example, if you choose to measure smaller capacitors with a low D value in a series circuit model, then you’re more likely to get inaccurate results.

On the other hand, measuring large electrolytes at a high frequency is likely to yield inaccurate results as well.

Inductance accuracy discrepancies:

Some inductors need to be tested with an added DC bias. You shouldn’t attempt this unless you find that your LCR meter supports this.

Resistance accuracy discrepancies:

Resistance can be measured in two ways, AC and DC measurements. While some meters can measure in both ways, others don’t. So, you need to refer to the manual for this too.

Some Measurement Tips

Here, you’ll find some measurement tips that’ll help you measure more accurately.

Measure the impedance of the application frequency

Not all LCR meters allow measuring the impedance of the application frequency. If your LCR meter allows you to do this, we highly recommend doing it.

The phase angle will help you determine whether the reactance is pure or a combination of reactance and resistance.

Then again, the impedance magnitude will allow you to be intuitive with your decisions.

Use 10nH for every cm for lead inductance

Typically, lead inductance that’s anywhere below 1 MHz isn’t much relevant, in most cases at least. You can measure this easily by using 10nH for every cm of the length of the lead.

Check the accuracy

It’s important to check the accuracy specifications of your LCR meter. Each LCR meter model comes with a different set of ranges and capabilities, and it’s important to know them all before jumping in.

This will also inform you about the maximum capacity of your LCR meter. You must never test any component that’s beyond the capacity of the LCR meter that you’re using.

Plus, you must keep in mind that changes in temperature can greatly affect the specifications provided in the manual. If the temperature of your environment is vastly different than the one mentioned in the manual, then you better contact support for further details and instructions.

Use old components as standard to check the device

Like every other electronic device, an LCR meter can go wrong anytime too. To ensure that you don’t suffer from any confusion or trauma of inaccurate reading, you need to stock some components that you’ve checked before.

Essentially, these components will act as standards for your understanding. Before operating the LCR meter, you need to check these out first to know whether the meter is working properly or not.

Never measure charged capacitors

Always discharge the capacitors completely before you measure them with an LCR meter.

Conclusion

An LCR meter is definitely an important and essential electronic device. However, it’s easy to go wrong with it unless you know how to use LCR meter properly. We highly recommend following our tutorial properly for getting an accurate read.

Resource Link:

  1. http://www.techni-tool.com/site/ARTICLE_LIBRARY/BK%20Precision%20-%20How%20to%20Use%20an%20LCR%20Meter.pdf

Leave a Comment