Using an LCR Meter to Test Inductors
An LCR meter is one of the most useful instruments for testing inductors. Unlike a standard digital multimeter, an LCR meter can accurately measure inductance (L), as well as other important characteristics such as Q factor, DC resistance (DCR) and, on some models, self-resonant frequency (SRF). LCR meters are widely used by electronics technicians, repair engineers, students and circuit designers.
What Does LCR Mean?
The name LCR comes from the three main passive components that the instrument can measure.
| Letter | Component |
|---|---|
| L | Inductance |
| C | Capacitance |
| R | Resistance |
Many modern LCR meters also measure additional parameters such as Q factor, dissipation factor (D), impedance (Z) and phase angle.
Measurements for Inductors
| Measurement | Purpose |
|---|---|
| Inductance (L) | Confirms the inductor value. |
| DC Resistance (DCR) | Checks winding resistance. |
| Q Factor | Indicates efficiency and losses. |
| Impedance (Z) | Measures opposition to AC. |
| Dissipation Factor (D) | Indicates energy losses. |
How an LCR Meter Works
An LCR meter applies a small AC test signal to the component and measures the resulting voltage and current. From these measurements, it calculates the component's electrical characteristics.
Because inductors behave differently at different frequencies, many LCR meters allow the test frequency to be selected.
Typical Test Frequencies
| Frequency | Typical Applications |
|---|---|
| 100 Hz | Large inductors and power components. |
| 120 Hz | Power supply components. |
| 1 kHz | General-purpose inductors. |
| 10 kHz | Small inductors and audio applications. |
| 100 kHz | RF inductors and high-frequency components. |
How to Measure an Inductor
- Disconnect power from the circuit.
- Remove the inductor from the circuit if possible.
- Select the inductance (L) measurement mode.
- Choose the recommended test frequency.
- Connect the test leads securely.
- Allow the reading to stabilise.
- Compare the result with the component value or datasheet.
Understanding the Results
| Reading | Possible Meaning |
|---|---|
| Correct Inductance | Component is probably good. |
| Very Low Inductance | Shorted turns or damaged core. |
| No Reading | Open winding. |
| High DCR | Damaged winding or poor connection. |
| Low Q Factor | Excessive losses. |
Advantages of an LCR Meter
- Measures inductance accurately.
- Provides more information than a standard multimeter.
- Useful for troubleshooting and quality control.
- Suitable for both through-hole and SMD inductors.
- Many models automatically identify component values.
Limitations
- Cannot always detect faults that occur only under high current or high voltage.
- Nearby circuit components may affect in-circuit measurements.
- Different test frequencies may produce different readings.
- Very large inductors may require lower test frequencies.
Common Measurement Errors
| Error | Cause |
|---|---|
| Incorrect Reading | Wrong test frequency. |
| Unstable Measurement | Poor probe contact. |
| Higher Than Expected DCR | Oxidised leads or damaged winding. |
| Incorrect Inductance | Component measured in circuit. |
| Fluctuating Display | Electrical interference or loose connections. |
Applications
- Repairing switch-mode power supplies.
- Testing speaker crossover inductors.
- Checking RF coils.
- Measuring motor and relay coils.
- Laboratory experiments and electronics education.
- Production quality control.
Interesting Facts
- Modern handheld LCR meters can measure components from nanohenries to several henries.
- Many professional LCR meters automatically compensate for the resistance of the test leads.
- Q factor measurements are especially important for RF inductors.
- Different test frequencies can produce noticeably different readings for some inductors.
- An LCR meter is one of the most valuable instruments for electronics repair and design.
Key Points
- An LCR meter measures inductance accurately.
- It can also measure DCR, Q factor and impedance.
- Always use an appropriate test frequency.
- Out-of-circuit measurements are usually the most accurate.
- Compare the measured values with the manufacturer's specifications whenever possible.