Measuring inductance

[grrr_arrghh]

Hi.

I have some small inductors lying around, and wondered how I could find out what inductance they are.

I have a multimeter, but obviously not one with inductance measuring.

Any ideas? (I'm hoping there will be some formulas relating to current, voltage etc...?)

Cheers,

Tim

 

[zachtheterrible]

https://www.lalena.com/audio/calculator/inductor/

This calculator will tell you the inductance. I think this one works good, but if it does not suffice, go to google and type in inductance calculator, that's how I found this one. If you want to do the math yourself, type in "Calculating inductance of an inductor" or something like that.

 

[Roff]

Unless you have an oscilloscope or a "grid dip" meter, it's going to be difficult. I'm assuming these are molded inductors, in which case Zach's equations won't help.

 

[chemelec]

There are Much better Calculators for inductance on my site at:
**broken link removed**

They allow for a Much greater wire range as well they take into account the Typical Insulation Thickness. Thats really important on smaller gauges of wire.

Take care....Gary

 

[grrr_arrghh]

thanks guys, but Ron H was right, they are molded. I did try looking at google first, but all the equations were relating to wire thickness and no. of turns etc.

You say it would be difficult Ron, is that difficult or impossible? i'm always up for a challenge!

Cheers,

Tim

 

[Nigel Goodwin]

thanks guys, but Ron H was right, they are molded. I did try looking at google first, but all the equations were relating to wire thickness and no. of turns etc.

You say it would be difficult Ron, is that difficult or impossible? i'm always up for a challenge!

There are a couple of basic methods of doing it:

1) Built an oscillator using the coil, and measure it's frequency.

2) Use a wheatstone bridge to compare it's value to a known inductor.

 

[stevez]

If you had an RF signal generator you might use that and measure the voltage at the terminals with inductor and capacitor of known value across the terminals as well. You'd need to make a simple RF probe from diode, resistor and capacitor so that your meter doesn't see the RF. While far from linear it may show dip/peak suggesting resonance. You'd have to depend on the calibration of the generator dial or do as I do, listen with general coverage receiver. This might take a little work as the inductor could be just about anything.

I mention RF signal generators because they seem to be fairly inexpensive at electronics flea markets.

 

[ante]

Tim,

Here is an easy to build adaptor for your multimeter:

Ante

 

[grrr_arrghh]

oo, thanks.

did that come out of a magazine? which one?

 

[Trini]

the ARRL Amateur Radio Handbook, don't remember which edition, had similar adapters for both Inductance and Capacitance.
If you are a true homebrewer get a February 2004 back issue of EPE magazine in your country and build the LCF meter. But this requires a programmed PIC microcontroller.
I have built a similar LC meter from info on the Internet that works like a charm. It does all the calculations for you and displays the L or C values on an LCD digital display.
The adapter however is simpler and cheaper.

Cheers,
Trini

 

[grrr_arrghh]

i've got the feb issue, i'll have a look. i've been meaning to foray into PICs for a while. And am I right in thinking that EPE have the code to download for free, from their website?

 

[Nigel Goodwin]

i've got the feb issue, i'll have a look. i've been meaning to foray into PICs for a while. And am I right in thinking that EPE have the code to download for free, from their website?

Yes they do, EPE are one of the best magazines for downloadable source code.

 

[ante]

Sorry Tim, I can’t remember where I got it.

Ante :roll:

 

[grrr_arrghh]

Sorry Tim, I can’t remember where I got it.

no worries, I was just interested.

 

[ante]

Tim,

I found the circuits talked about earlier if you havent decided yet!

Ante :roll:

 

[ante]

Tim,

I found the circuits talked about earlier if you havent decided yet!

Ante :roll:

 

[grrr_arrghh]

cheers Ante, I keep thinking I could do with a cap meter...!!

Thanks again everyone

Tim