I'm reviewing a set of inductors for the Experimenting with Magnetic Components design challenge. In this post: verifying the datasheet specifications with an LCR meter. The inductor is #7 of the kit: Bourns RF Choke, Molded Choke, 9250A Series, 1.8 mH, 50 mA, 29.9 ohm, ± 10%, 1 MHzBourns RF Choke, Molded Choke, 9250A Series, 1.8 mH, 50 mA, 29.9 ohm, ± 10%, 1 MHz
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An LCR meter is an instrument to measure impedance: how inductors, capacitors, resistors behave at a given frequency.
They are often able to show additional information, such as DC resistance, phase angle, Q factor.
The one that I'm using, a Voltcraft LCR-400, is identical to the GW-INSTEK LCR-916.
It can measure
- L/C/R at 100 Hz, 120 Hz, 1 kHz, 10 kHz, 100 kHz.
- the trio Phase angle (θ), Dissipation factor (D = tanθ) and Quality factor (Q = 1/D)
- Equivalent series resistance
- DCR: Resistance at 0 Hz
If you're interested in probing techniques for LCR meters: fmilburn's DIY 3-D Printed 4-Wire Kelvin LCR Adapter for SMD Components is the place to check.
The Inductor according to the datasheet
L: RF Choke, Molded Choke, 9250A Series, 1.8 mH, 50 mA, 29.9 ohm, ± 10%, 1 MHzRF Choke, Molded Choke, 9250A Series, 1.8 mH, 50 mA, 29.9 ohm, ± 10%, 1 MHz
source: Bourns datasheet
The component is measured at 250 kHz. Bold values are ones I measure later with the LCR meter.
L: 1.8 mH
Q: >= 45
Self resonance frequency >= 1 MHz
DCR: <= 29.9Ω
The Inductor as tested by an LCR meter
image source: the actual component in the kit
I'm measuring at 100 kHz, maximum frequency of my meter.
I'm using the 4-wire probe points on the meter, and have calibrated the instrument for that.
L: 1.7184 mH
Q: 47.7
DCR: 17.88 Ω
R (ACR, Z): 22.63 Ω
ESR: 22.5Ω
θ: 88.7°
D: 0.021
