Is my meter faulty?

[vlad777]

I just bought DMM(with LCR on it) VC9805, just to be able to measure inductance.
I am getting strange results so I want to ask you could it be correct?

**broken link removed**

For both of these I get less then 100 micro Henry. (87uH and 8uH)

Is this correct or meter is faulty?

Many thanks.

 

[Nigel Goodwin]

They look VERY small value inductors (hardly any turns on them), so quite probably correct.

 

[vlad777]

From number of turns(33), diameter(5mm) and length(24mm) for the second one I get 1uH if it is air coil.
But this coil has ferrite core, and ur should be about 300.

Relative Permeability μ/μ0
Ferrite (nickel zinc) 16–640
Ferrite (manganese zinc) 640 (or more)

 

[colin55]

What you do is read a known small value of inductance - say about 10 or 100 times the value of the unknown inductance. Then connect the unknown and known inductances in series. You will get the addition of the two. This is the way to read inuctances that may be too low for your meter. And also confirms the reading. Two inductances in series ADD together just like resistors.

 

[kinarfi]

This may be a bit of hi jacking, hope not, but my guess is that vlad777 is experimenting with inductors and so am I, so what would a 10uH 10 amp look like, how many turns, what size wire, would you have to have a core or would an air core work? frequency around 500KHZ. --- Never mind, I found some pictures and specs in catalogs.
Thank you,
Kinarfi
Thought I cancelled this post, since I didn't, I'd like to ask a question, 2 inductors in parallel of the same H = 1/2 H, and add if in series, like resistors, correct? When I measure the inductance of toroid inductor that has 3 separate equal winding, I get 10uh each, if I parallel them, I still get 10uh, I assume that parallelling them amounts to the same as one winding with larger wire. I didn't think to series them, but I did earlier on a different inductor and if I remember correctly, the inductance multiplied.
Thanks,
Kinarfi

 

[Nigel Goodwin]

From number of turns(33), diameter(5mm) and length(24mm) for the second one I get 1uH if it is air coil.
But this coil has ferrite core, and ur should be about 300.

I would suggest you're wildly out in your figures!.

Ferrite cores have hugely different characteristics.

 

[vlad777]

Kinarfi , both inductors on the picture where yanked from PC PSU.
They were filters on output voltages. Do you need them for this purpose?
PSU output currents are 10-20A or something like that but I never knew the value
of the chokes, that's why I'm confused here.

To your second question: inductors must not share the same core if you are to treat them as two separate inductors in series or parallel.

If you series two coils on the same core it's like adding some turns to the same inductor, and inductance is square-like dependant on N.