Practical - 14 :- Identification of Different Types of Inductors and their Specifications

1. Aim / Objective

To visually identify various types of inductors and to experimentally determine their key specifications, including Inductance (), DC Resistance (DCR), and Quality Factor (Q).

2. Apparatus Required

Sr. No.	Component / Equipment	Quantity
1.	Assortment of Inductors (Air-core, Ferrite-core, Iron-core, Axial, SMD)	1 of each
2.	Digital LCR Meter	1
3.	Digital Multimeter (DMM)	1
4.	Connecting Probes	1 set

3. Theory

An inductor is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. It is formed by a coil of wire, often wound around a core. An inductor's primary function is to resist changes in electric current. The relationship between the voltage (), current (), and inductance () is described by the formula:

The main specifications of an inductor are:

• Inductance (L): The measure of an inductor's ability to store magnetic energy for a given current. Its unit is the Henry (H).

• DC Resistance (DCR): The ohmic resistance of the conducting wire that forms the coil. It is measured with a multimeter. For an ideal inductor, DCR would be zero.

• Quality Factor (Q): A dimensionless parameter indicating the efficiency of an inductor. It is the ratio of its inductive reactance () to its resistance (DCR) at a specific frequency (). A higher Q factor signifies lower energy loss.

Inductors are classified based on their core material (Air, Iron, Ferrite) and their physical construction (Toroidal, Axial, SMD). The core material significantly influences the inductor's magnetic properties and its suitable frequency range.

4. Measurement Setup

a) For DCR Measurement:

Air Core Inductors    Ferrite Core    Chip Inductors

                                     Inductors

           

Figure 1: Measuring DCR with a Digital Multimeter

b) For Inductance (L) and Q Factor Measurement:

Ferrite Beads & Cores    Shielded Inductors

          

Figure 2: Measuring L and Q with an LCR Meter

5. Procedure

1. Collect all the inductor samples.

2. Visually inspect each inductor and classify it based on its physical appearance and core material (e.g., Air-core, Ferrite-core, etc.). Note down its appearance in the observation table.

3. To Measure DCR:

   • Set the Digital Multimeter (DMM) to the lowest resistance () range.

   • Connect the DMM probes across the terminals of the first inductor.

   • Record the stable resistance reading as the DCR.

4. To Measure Inductance (L) and Quality Factor (Q):

   • Turn on the LCR meter and set it to measure Inductance ().

   • Set the test frequency to a standard value, such as 1 kHz.

   • Connect the inductor to the LCR meter's test terminals.

   • Record the Inductance () and Quality Factor () values displayed by the meter.

5. Repeat steps 3 and 4 for all the remaining inductor samples.

6. Carefully record all readings in the observation table.

6. Observation Table

Test Frequency for L & Q Measurement = 1 kHz

Sr. No.	Type of Inductor (Visual Identification)	Visual Characteristics (Shape, Core, etc.)	DC Resistance (DCR) ()	Inductance (L) (H, mH, or H)	Quality Factor (Q) (Dimensionless)
1
2
3
4
5

7. Conclusion

The different types of inductors were successfully identified. Their specifications were measured and it was observed that the inductance value is significantly affected by the core material, with _______ core inductors showing higher inductance. The DCR was found to be dependent on the length and thickness of the wire coil. The relationship between an inductor's physical construction and its electrical properties was thus experimentally verified.

8. Precautions

1. Handle all electronic components and instruments with care.

2. Ensure that the DMM and LCR meter are set to the correct measurement mode before connecting a component.

3. Ensure a firm and proper connection between the component leads and the meter probes to avoid errors in readings.

4. For SMD components, use appropriate fine-tipped probes or tweezers to ensure good contact.