LCR meters are frequently used to measure the inductance of inductors. It is also the simplest way. However, you could always use an oscilloscope to measure inductance. But without an oscilloscope LCR meters should be your priority while measuring inductance.
Henries is the unit of inductances. The change in current flowing through a current-carrying coil tends to oppose it. Simply said, inductance opposes any sudden shift in the current. The current waveform of an inductive impedance will lag after the voltage waveform.
Measure Inductance Without Oscilloscope
A coil’s self-inductance is denoted by the symbol L. Coils generate EMF when the current(i) passes through the changes. The induced EMF(V) is proportional to the rate of current change (di/dt). As a result, E ∝ di/dt. Hence, E=L*(di/dt). In this case, L represents inductance.
Inductance is the ratio of induced voltage to the current rate of change. The direction of this induced EMF, according to Lenz’s law, is such that it opposes the change in the current for which the EMF was generated in the first place. The methods to measure inductance without an oscilloscope are illustrated below:
Method-1: Using an LCR meter
LCR meters work by supplying an alternating current voltage to the device under test. They measure the resulting current in terms of amplitude and phase relative to the alternating current voltage signal. Perform the following steps to measure inductance:
Step-1: Turn on the LCR meter and wait for it to light up. A basic LCR meter is similar to a multimeter, which is generally used to measure voltage and current. Most meters are handheld with a readout screen that displays 0 when the power button is pressed. If it does not show 0, hit the reset button to reset the meter to 0.
Step-2: Set the LCR to measure L, also known as inductance. An LCR meter captures multiple measurements, which are displayed on the dial. Because L stands for inductance, it is the one you require. Turn the dial of a portable meter to the L position.
Figure: Dial of an LCR meter.
Step-3: Set the meter to 1 volt and 100 kHz. LCR meters often include a variety of test settings. The lowest inductance test is usually around 200 µH. When calibrating a tabletop meter, 100 kHz at 1 volt is ideal for most devices.
Figure: Setting the voltage and frequency range.
Step-4: Connect the LCR meter to the leads. The meter, like a multimeter, will have a black and red lead. The red lead goes into the positive plug, while the black one goes into the negative plug. To begin transmitting a current through the device, connect the leads to its terminal ends as the following figure.
Step-5: To determine the inductance, look at the display screen. LCR devices do inductance testing almost instantly. You should immediately see a change in the reading on the screen. It will display a number in microhenries (uH). You can turn off the meter and remove the gadget after you have the number.
Method-2: Using a Multimeter
Measuring inductance with a multimeter requires specific and costly circuitry. Because inductance measurements are only required on a few occasions, ordinary multimeters lack this capability, allowing for reduced costs. But a complex process illustrated below can be followed to measure inductances with multimeters.
Step-1: Measure the resistance(r) of your inductor.
Step-2: Connect the circuit like the following figure. Use a resistor(R) of known value.
Step-3: Set the frequency between 2kHz to 10kHz.
Step-4: Note the voltage of the resistor(R) using the multimeter. Mark the voltage as ‘x’.
Step-5: Use the following relation of the figure to find inductance, L:
Method-3: Voltage-Current Slope
The final approach is the most complicated, requiring a pulsed voltage to be applied across the inductor and then monitoring the current. The duty cycle of the pulse should be less than 50%. To avoid saturation, utilize a high frequency as well. This necessitates the use of a current sense resistor or current probe.
On the scope, the current is indicated, and the slope determines the inductance. The slope is calculated by dividing the peak current Ipk by the time Ton. Inductance, L= V*Ton/Ipk.
What Instrument Measures Inductance
There are various instruments out there to measure the inductance of your inductor. The most frequently used ones are given below:
- Oscilloscope.
- LCR meters.
- Frequency counter.
- Inductance meter.
Uses of Inductors
Inductors are commonly used to store energy. These components are frequently utilized in tuning circuits, transformers, inductive sensors, induction motors, and other applications. Given the importance of inductors, inductance measurement is required.
Conclusion
Inductance is often measured in millihenrys or microhenrys. A frequency generator and an oscilloscope or an LCM multimeter are typically used to measure it. A voltage-current slope monitoring the change in the electrical current traveling through the coil can also be used to calculate it.
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