Coils are used not only for electric generators and motors but also for products in various industries such as IC cards, mobile phone chargers, and antennas. This section introduces examples of observation and measurement of coils using digital microscopes.

Observation and Measurement of Coils Using Digital Microscopes

What is a Coil?

The structure of a coil is basically an electric wire wound around many times. Many products take the shape of a coil, such as springs, and those used in electrical circuits are literally called coils (inductors). Coils can form resistors, capacitors, and inductors, which are all passive elements used in electrical circuits.

Types of Coils

Coils are classified into different types according to the wire winding shape, structure, and function.

Classification by wire winding shape

Solenoid type

This type is easy to wind and is commonly used. There is a large amount of leakage flux.

Toroidal type

This shape reduces the leakage flux.

Spiral type

The wire winding can be planar, which is suitable for inclusion in chips.

  • A: Magnetic flux

Classification by structure

Wound coil
In this structure, a copper wire covered with an insulator is wound in a spiral.
Laminated coil
The coil is formed by laminating multiple conductor layers on a sheet or PCB. This structure is compact and has excellent frequency characteristics.
Thin film coil
The coil is formed with metal film that is thinner than printed conductors by sputtering or using deposition techniques. Compact and highly precise coils can be manufactured.

Classification by function

Choke coil
Coils used in power supply circuits are called choke coils. Chokes smooth out power supply and eliminate noise.
Tuning coil
Signals at specific frequencies can be extracted. Tuning coils are used for wireless circuits and audio circuits.
Antennas are made by wrapping a conducting wire around a ferrite rod and are used for AM radio.
Transformers are also a type of coil that are used to convert AC voltage and voice signals.

Coil Observation and Measurement Examples Using Digital Microscopes

These are the latest examples of observation and measurement of coils using KEYENCE’s VHX Series 4K Digital Microscope.

Observation of wire winding conditions in a motor
50×, ring illumination
3D measurement of scratches on a motor coil
500×, coaxial illumination
Observation of a coil’s fracture surface

700×, ring illumination + Optical Shadow Effect Mode image

Using the Optical Shadow Effect mode reveals fracture and surface irregularities.