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Step 2Ferrous Core Materials
On further investigation, an aluminum carabiner does not encourage inductance. A ferrous material is needed. According to this inductor manufacturer, a "core material with a higher permeability than air confines the magnetic field closely to the inductor, thereby increasing the inductance." Classically described, iron has unpaired electrons in its orbital shells that create a polarized atom and these atoms easily arrange and encourage inductance whereas aluminum's electrons are not organized to create a polarized atom and hence the atoms do not arrange about a magnetic field.
Steel alloys are mostly iron. The results were outstanding.
Starting with the highest resolution:
1-1/2" C-Clamp ~$1.00
0.45 AAC/mVAC consistent within 0.21 amps between 5 to 12 amps
5/16" steel/zinc U-Lock ~$1.00
1.0 AAC/mVAC consistent within 0.50 amps between 5 to 12 amps
1/4" x 2" zinc U-bolt with nuts $0.75
1.70 AAC/mVAC consistent within 0.65 amps between 5 to 12 amps
1.5" Key Ring ~$0.70
5.9 AAC/mVAC
Lastly, results may improve with tighter wrapping of the wire to the core material.
Steel alloys are mostly iron. The results were outstanding.
Starting with the highest resolution:
1-1/2" C-Clamp ~$1.00
0.45 AAC/mVAC consistent within 0.21 amps between 5 to 12 amps
5/16" steel/zinc U-Lock ~$1.00
1.0 AAC/mVAC consistent within 0.50 amps between 5 to 12 amps
1/4" x 2" zinc U-bolt with nuts $0.75
1.70 AAC/mVAC consistent within 0.65 amps between 5 to 12 amps
1.5" Key Ring ~$0.70
5.9 AAC/mVAC
Lastly, results may improve with tighter wrapping of the wire to the core material.
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the digikey looks like ~$11 for a 1" diameter ring. I couldn't see the dimensions on the radio shack item but half the price. I'd really like to see how the performance matches up so I'll probably try one out eventually.... so you say there's ferrous in a monitor cable too? can you add to that, cause I didn't see any last time I checked.
You should get better results with iron than steel. whats the difference? from what I can remember, iron has more iron in it. Impurities are added to steel to make it stronger (~ 1% carbon for instance). Iron often appears rougher, darker, and rusts a lot easier.
regardless, I think you should get good results with the steel. what kind of AAC/mVAC are you getting?
1" is probably bigger than necessary for most applications. I was thinking about 495-3856-ND which has a inner diameter just under 1cm, which should be plenty to go around most any power cable I would measure, even with the thickness of the windings.
Ferrite is very brittle, so it is probably not feasible to cut it to make something that snaps together. However, for my application it is probably okay to have a solid ring (I would have to break the circuit to put the ring around one wire.
The Radio Scrap snap together choke would be a pain to wrap, because of its length. But, it does snap together - and is easily available. (Hard to justify a $1 digikey order).
I saw no deflection on my analog voltmeter set to a 300 mA range. I may not have given it enough load, though - I think I was drawing less than an amp.
At ~1/2 amp you would only see 1 mVAC on your voltmeter using an arrangement similar to the C-clamp. As you play around with materials you may also want to try more windings. Also, I tried once with uninsulated wires and it didn't work so don't go that route.
thanks for the lead on the monitor cables.... Sense I've been looking for ferrite it is kind of hilarious that it turned out to be so close.
By the way, Radio Shack has some toroids too, along with a different snap-together choke that might be much better for this application, although at $8, it alone breaks the $5 price point. www.radioshack.com/family/index.jsp?categoryId=2032273 at the bottom of the page.