Understanding Inductance: Converting Units with Confidence

When it comes to any electrical or electronic circuit, one of the main basic parameters that engineers, students and hobbyists need to be aware of, is inductance.

A Quick Introduction to Inductance

An inductor – also sometimes referred to as a “coil” or a “choke” – is a passive electrical component that opposes sudden changes in current. It serves the purpose of slowing down current surges or spikes by temporarily storing energy in an electromagnetic field, prior to releasing this energy back into the circuit.

The ability of an inductor to store energy is known as inductance.

It was the American physicist Joseph Henry (1797-1878) who first recognised the phenomenon of self-induction, whereby a changing current in a coil induces a voltage (electromotive force or EMF) within the same coil.

To this day, the unit of magnetic inductance is the henry, named in his honour.

Why Are Unit Conversion Skills Important When It Comes to Inductance?

In common with resistance and capacitance, inductance is a basic electrical parameter that impacts on all circuits to a degree.

So, with inductance being such a fundamental property of electrical circuits, it is vital for engineers to understand what inductance is, while also having the ability to confidently convert between the various scales of inductance.

After all, in practical circuits, inductors are frequently specified in millihenries, microhenries, or even nanohenries. Being able to convert between such units is particularly crucial when it comes to such applications as filters, transformers, and motors.

What Are the Common Inductance Units?

Bearing in mind how widely inductance values in circuits can vary – from tiny coils in electronics to huge transformers in power systems – here are the primary inductance units to be aware of:

• Henry (H), which is the base SI unit, typically seeing use in large inductors, such as in power electronics
• Millihenry (mH), which is routinely used in audio circuits, filters, and small transformers
• Microhenry (µH), which sees use in high-frequency circuits such as RF applications
• Nanohenry (nH), which is found in microelectronics and PCB traces.

The Conversion Factors for Scales of Inductance

You can apply the following relationships to convert between the aforementioned units of inductance:

• 1 H = 1,000 mH = 1,000,000 µH = 1,000,000,000 nH
• 1 mH = 0.001 H = 1,000 µH = 1,000,000 nH
• 1 µH = 0.000001 H = 0.001 mH = 1,000 nH
• 1 nH = 0.000000001 H = 0.000001 mH = 0.001 µH

A conversion table is provided below:

How, Then, Do You Convert Between Scales of Inductance?

The process can be described as follows:

• First, you identify the starting unit, such as mH, and the unit to which you wish to convert, such as H.
• Then, you apply the conversion factor – multiplying or dividing by the appropriate power of 10, referring to the above table.
• When you carry out the calculation, we suggest that you do so manually in addition to using a reputable calculator to perform the same conversion. This will allow you to verify the accuracy of the result.
• Check the order of magnitude to ensure the result makes sense. µH values, for instance, will be bigger than mH values.
• Record the result using the correct units, so that you don’t get confused when referring to it at a later stage of the circuit design process.

That’s it! While there are inductance unit conversion calculators you can find online that enable you to convert inductance values easily and quickly, you should also make sure you are adept and confident in performing such conversions manually.

This capability and confidence, in turn, will aid you significantly throughout even the most specialised and demanding circuit design projects you take on as an electrical engineer, hobbyist, or student.