Assuming the sensed current in the coil is reasonably sinusoidal, skin depth at 100KHZ is about half the diameter of AWG 28, (if the winding is only one layer thick). This means that the entire wire cross sectional area will be carrying current. This was my reason for suggestion that particular wire size. Actually, given the very small level of induced current (probably microamps or less), it really makes no difference at all what wire is used. Even AWG 14 will do the job nicely since even though only the skin of the larger size wire will be carrying current, there will still be far more actual effective conducting area than is needed for such a miniscule current. It's not like this is a high power switchmode power supply transformer, or something like that, where current density in the wire is high and minimizing eddy current losses is critical. Bob Wilson TIR Systems Ltd. Vancouver. -----Original Message----- From: Ken Javor [mailto:[email protected]] Sent: June 20, 2002 6:31 PM To: Robert Wilson; [email protected] Subject: Re: magnetic field measuring instruments and probes I was simply reporting the military standard construction. I haven't done the analysis to determine skin effects and whether using Litz wire to counter it is useful.
---------- From: "Robert Wilson" <[email protected]> To: <[email protected]> Subject: RE: magnetic field measuring instruments and probes List-Post: [email protected] Date: Thu, Jun 20, 2002, 5:06 PM Litz wire at 100KHz sounds a little over the top. AWG20 or 30 will do the job nicely. Bob Wilson TIR Systems Ltd. Vancouver. -----Original Message----- From: Ken Javor [mailto:[email protected]] Sent: June 20, 2002 7:11 AM To: Istvan Novak; [email protected] Cc: Istvan Novak - Board Design Technology Subject: Re: magnetic field measuring instruments and probes At the low end you could use a 13 cm loop such as that used for military RE01/ RE101 testing (36 turns of 7-41 Litz wire, electrostatically shielded). That loop can be used from 30 Hz to at least 100 kHz. It is handy because it is small and can be used as a probe. There are numerous loops developed for VDE testing that operate from 10 kHz to 30 MHz. But these loops are physically large and developed for use at 3 meters from the test item. There are also close field probes for diagnostic testing, but these have large antenna factors. So the answer depends on your specific need. ---------- From: "Istvan Novak" <[email protected]> To: <[email protected]> Cc: "Istvan Novak - Board Design Technology" <[email protected]> Subject: magnetic field measuring instruments and probes List-Post: [email protected] Date: Thu, Jun 20, 2002, 7:28 AM Hi list members, Could someone suggest or refer me to pointers/manufacturers of probes and instruments to measure magnetic close field in the 10kHz to 10MHz frequency range? High accuracy is not important, values to be measured would be around 0.5mT and up. Thanks Istvan Novak SUN Microsystems
