You have a DIY inductor and no LCR-meter at hand? – No problem.
A known resistor in series, and some calculations make the day.
L = R * sqrt(3) / ( 2 * π * f )
Example
Measurements:
* R1 = 99.82 Ω
* Vout = Vin / 2 at 901 khz ( 901,000 Hz )
=>
L = 99.82 * sqrt(3) / ( 2 * π * 901,000 )
=>
L = 99.82 * 1.732 / ( 2 * 3.14159 * 901,000 )
=>
L = 30.54 µH
Btw. – The geometry of the DIY inductor:
* Turns: 43
* Coil diameter: 29 mm
* Coil length: 34 mm
* Wire diameter: 0.71 mm
* Core: Air
Capacitance
If you measure across the resistor, you can swap between an inductor and a capacitor.
The formula for capacitance is only slightly different – R is on the bottom:
C = sqrt(3) / ( 2 * pi * f * R )
Inductance, 2nd method
If you are measuring the peak to peak voltage across the inductor, then use this equation:
L = R / ( 2 * pi * f * sqrt(3) )
Note that the stimulation frequency is 3 times higher when measuring across the resistor, compared to across the inductor.
Depending on the frequency range of your equipment, and the self resonance of the inductor, there may be times when one method is preferred over the other.
