# inductance measurement

Discussion in 'The Projects Forum' started by antony.prathiban, Jun 18, 2008.

1. ### antony.prathiban Thread Starter Member

May 14, 2008
24
0
i have an induction heating coil.
now, i need to measure the inductance(L) of the coil.how should we measure the coil inductance?is it possible using multimeter.
could you please anyone explain me.

2. ### antony.prathiban Thread Starter Member

May 14, 2008
24
0
is it possible without LCR meter.?
and how ?

3. ### thingmaker3 Retired Moderator

May 16, 2005
5,073
8
There are a couple circuits on the web for making an inductance meter. They are basically oscillators allowing us to measure the inductive reactance. At least two of them make use of an ordinary multimeter to make readings.

Note that if the workpiece is martensitic or ferritic steel or iron, the inductance of an induction heater coil will change as the work-piece heats up.

4. ### mik3 Senior Member

Feb 4, 2008
4,846
70
Apply a low AC voltage across the coil and measure the current through it. Then divide the AC voltage by the current to find the coil's reluctance.
Then the reluctance of the coil equals 2*3.14*f*L

where f is the frequency of the AC voltage
L is the inductance

Solve for L to find the inductance.

It would be safer to include a resistor in series with the inductor as not to burn the inductor if it has low inductance and draws exessive current but you will need a bit more complicated calculations.
Also, note that you wont find the exact value of the inductor because the wire itself has resistance, so if you want exact calculations measure this resistance with a multimeter and include it in your calculations.

5. ### Wendy Moderator

Mar 24, 2008
21,698
3,000
I vaguely remember circuits that will convert a capacitance to a virtual inductance. If we could reverse the process, convert an inductance to a virtual capacitance, then we would have an inductance meter using the capacitance meter on most DVMs.

I'd be interested in a piece of equipment like myself. The memory is vague for the conversion though, it had to do with active filters, I remember that much. If I come across it or remember it I'll put it up.

6. ### Wendy Moderator

Mar 24, 2008
21,698
3,000
Found it. It's called a Gyrator.

I'm not sure what would happen if we substituted a coil for the cap, but the circuit points the way. Any ideas?

I think it might work well with a straight substitution of the coil for measurement within a DVM.