Right here a easiest yet quite precise inductance meter is introduced, which is often developed within couple of minutes. Moreover, the circuit may be powered-up with a single 1.5V cell. In spite of this, a frequency meter could well be needed to work-out the inductance.
The circuit is fairly self-explanatory in which, two NPN transistors are cross-coupled to form a flip-flop oscillator. The values of R1 and R2 could possibly be anything between 47 - 100R. The frequency of the oscillation is oppositely proportional to the inductance and it could be measured with the following formula:
Frequency (kHz) = 50 / Inductance (uH)
CALIBRATION:
In the beginning the circuit needs to be calibrated utilizing a known inductor, as identified below:
Think, we certainly have an inductor of 100uH. Putting the value of inductor (100uH) in the above formula, we get 500kHz.
Hook up the inductor cross point A & B and power on the circuit. It is going to begin oscillating.
Attach the frequency meter at point A or B and ground.
Regulate the POT until the meter reads 500kHz. Now the circuit is calibrated.
INDUCTANCE MEASUREMENT:
Hook up an unidentified inductor across A & B.
Power on the circuit and study the frequency at point A or B.
The above formula may also be published as:
Inductance (uH) = 50 / Frequency (kHz)
Placing the value of frequency in this formula, the value of the inductor can be obtained.
Waveform Image:
I don’t understand where that number 50,000 comes from.
Thanks
sorry, it should be actually 50 and not 50,000. It’s probably the oscillating frequency of the transistor multivibrator…
Won’t the winding capacitance of the inductor affect the resonant frequency and so skew the result?
It is amazing, if it is working.
I will try it.
Thank you so much.