Inductive Coupling Coefficient

See reply to what3rd who did an excellent 'rule-of-thumb' estimate.

I was VERY surprised to see approximately 0.1 coupling!

If you're stuck on using this approach, and need a model; I've already got the .asc running for various positions. However, it's easy to do a curve fit and produce k vs position, too.

Is this for isolation? high voltage separation? Have you thought of using those cheap LED 'handheld remote controllers' They transmit quite a distance, cost nothing and run on nothing, ...well almost. but you get to piggy back on VOLUME production costs. Bunch of chipsets out there.

This is one of those "I wouldn't do it this way", but I'm looking into it at the insistence of the client. ...Jim Thompson

Easily. I assumed mainly that the faces of the send ferrite were point sources, and that the receive winding was at the midpoint of the ferrite (this would be the main error). In a real environment, you can position copper (or brass... anything dielectric) to shape the field and get maybe another factor of two.

Last time I did a finite-element model, I had to write all the code myself...

whew! but still, will have your name on it when finished.

However, I just confirmed that using a rod that is 5mm diameter by 1cm long and the permeability changes from 2000 down to 1000 you only get about 0.3% change in inductance. [remember I said a function of aspect ratio?] which means *if* you tune the inductor, it will stay pretty much in tune. At least for a Q of 100 and that should be good enough for peaking the signal AND getting 1kHz through on a 100kHz carrier. [more possible but allow some sloppiness] and 1kHz sidebands means at least

The answer is yes it can be done that way.

That's OK. If I design it... it _will_ work >:-}

...Jim Thompson

glad to hear that's within error band, didn't want to insult you.

I use femm 4.2, Dr. David Meeker did an incredible job on this piece of software.

Interesting you mention copper to shape the field. Most people only think of ferrous material to shape a field, but conductive can shape also, at frequencies. Remember Ampex and their audio tape recorder which used 1+ Mhz bias and then placed a copper wedge inside the magnetic gap of the record head in order to force the field out more into the tape, accomplishing two things, 6dB increase in S/N AND the fields were more perpendicular to the surface! Only 3 built, I got to hear one back in the days. Ran super HOT. But sounded incredible!

...all the code yourself?! wow NOW I'm impressed!

Wasn't questioning that aspect, just the "why did he do it this way?" aspect. and NOT even use vacuum tubes!

-Lasse

Doing some housekeeping of my PSpice symbol library I noted that, in the past, I created symbols for triode, tetrode, and two pentode symbols, dependent on number of grid pins that come out, so I'm ready

...Jim Thompson

Thanks, Lasse! ...Jim Thompson

How about Interociter parts?

I've done tube designs, back when they were the only devices that could handle 10-20kV

I finally successfully replaced in one location, the high voltage drivers. Using [Delco?] 1200Vceo NPN transistors and a step up transformer ...inside the loop to remove the characteristics of the transformer. All to get accurate 5kVpp audio sawtooth waveforms [better than 0.1% linearity] not bad when you consider those !@#$#! resistors have voltage coefficients that're out of sight!

longer,

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OK fine. Galvanically isolated to very many kilovolts? Why do they want this?

?-)

Doesn't TI make a chip good for the low KV region?

Two separate boards, not just an isolation barrier. ...Jim Thompson

Maybe use a toroid, Teflon winding on the HV side, use left qtr for pri, right qtr for sec, dip in Glyptal?

Customer built a PCB and is getting good data coupling out to 2" spacing.

Both ends are tuned with Q~10, so I'm going to cut it back a bit, I fear cross-talk issues when he implements multi-channels. ...Jim Thompson

Can he put alternate channels on the opposite side of the board? Or maybe a EMI shielding enclosure, might cause a change in the inductance of the coil a bit.

Cheers