choke, inductor coil, values

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GlassWolf

Copper - Posts: 365

Joined: June 22, 2002

Location: South Carolina, United States

Posted: July 01, 2002 at 2:52 PM / IP Logged

Okay, using my DMM, how can I measure the value of a choke? (in milliHenries)

I have a few here for a low-pass crossover, or second-order low-pass/high-pass, but the values are long-gone.

I can't for the life of me recall how to measure the value on a coil. resistors and caps I can handle heh

thanks

-GlassWolf

Pioneer Stage-4, Orion, DynAudio, Fi

NyxBass

Silver - Posts: 226

Joined: March 14, 2002

Location: United States

Posted: July 01, 2002 at 6:53 PM / IP Logged

Off the top of my head, it's rated by the size of the wire related to the amount if turns and layers.

I'm not sure with a DMM if you can measure it.

I have a book for formulas for air core coils, but you have to know the number of turns, total length of wire and such. I can give thewm to you if they'd be useful...

/NyxBass

GlassWolf

Copper - Posts: 365

Joined: June 22, 2002

Location: South Carolina, United States

Posted: July 01, 2002 at 7:31 PM / IP Logged

yeah I know how a coil is made LOL that came with my EE degree.. what I forgot was a way to measure the value of one sitting in front of me. I've got about 3 small ones sitting downstairs on the bench I need to find values for, although I will most likely just run to rat-shack wed. morning and pick up some new ones with caps etc for the second-order high-pass crossover I need to build (2 pair of them actually)

that way I can cross my mids over at 150Hz with a 12dB roll-off instead of the electronic crossover's built-in 80Hz 18dB/octave set point for high-pass. they'll have a more gentle roll off and stop bottoming out at high volume for me LOL

-GlassWolf

Pioneer Stage-4, Orion, DynAudio, Fi

awd_sr

Copper - Posts: 84

Joined: June 04, 2002

Location: United States

Posted: July 01, 2002 at 8:10 PM / IP Logged

I dont know if a standard multimeter can measure inductance, you can buy a kit to use with a meter, but the readings aren't accurate. If they are air-core, the formulas will let you know based on the thickness/gauge of the wire, the length, and the number of turns.

If I'm wrong, I'd love to find out how to do this. As well as measure cap values with a standard meter. I know Ive seen kits that u can build to do this, maybe like under 10 bucks a piece.

go2pac

Copper - Posts: 179

Joined: May 04, 2002

Location: California, United States

Posted: July 01, 2002 at 8:38 PM / IP Logged

You can't measure it with a DMM alone, to many variables. You either need a signal generator and a known capacitor value or a inductance meter.

Karl

Pacific Accessory Corporation

Mobile Audio Interfacing Equipment

Connecting You to Your Music Since 1976

GlassWolf

Copper - Posts: 365

Joined: June 22, 2002

Location: South Carolina, United States

Posted: July 01, 2002 at 10:51 PM / IP Logged

bah I'll just buy new ones then LOL!

actually regarding capacitors, my DMM measures them. It has two slots for reading the capacitance by inserting the two leads into the meter.

I'll go grab ya a picture of it. hold on.

choke, inductor coil, values - Last Post -- posted image.

I love this meter, the only drawback was that right after I bought it, they came out with a new model with a frequency generator in it LOL

Ah well for $100 I can't complain I suppose. retail was like $150

has a PC-interface and all, and i got some useful adapters for it as well. heavy-duty coiled-cord probes, gator-clip ends, pin-ends, wire-grabbing ends, and insulation-piercing ends.

All have come in great handy at times in car work.

-GlassWolf

Pioneer Stage-4, Orion, DynAudio, Fi

awd_sr

Copper - Posts: 84

Joined: June 04, 2002

Location: United States

Posted: July 02, 2002 at 8:43 AM / IP Logged

thats pretty sweet man, that u can hook it up to the CPU

Now that I think about it, my meter has slots for testing transistors, so maybe I can switch it to test caps too....I hope so

off the subject, have you seen any free software for the CPU that allows u to use your soundcard and displays a spectrum analyzer on the monitor? i found one like this for an o-scope, but no luck on the SpecAn.

GlassWolf

Copper - Posts: 365

Joined: June 22, 2002

Location: South Carolina, United States

Posted: July 02, 2002 at 1:37 PM / IP Logged

I'd love to be able to convert my computer into an RTA! heh damn that'd be sweet.

No I haven't seen or even thought to look for such software.

I'll have to nose around. Then I'd have to find a good mic for it too, with the proper response curve. The best soundcard I know for doing this would be the TerraTec DMX 6Fire 24/96. It's a semi-pro level digital recording card similar to the SB Audigy, but with a brick-wall-flat recording curve. very sweet card for about $260 street.

As for the transistors, yeah mine can do hFE package transistors as well, and has that second port for caps. can even read frequencies up to 200KHz.

no luck on a signal generator for inductance though LOL

-GlassWolf

Pioneer Stage-4, Orion, DynAudio, Fi

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choke, inductor coil, values

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