Victor, The dissipater surface has to be metallic, likewise the heatsink. Without compression, the capacitance between the two metal surfaces is measured. Compressed, the measurement is repeated. C is proportional to A/D, with dielectric constants unaltered. A (interface area) is unchanged, and the uncompressed thickness D is known. Usually, the distance isn't a critical feature. There are mechanical issues, though, and in one case I ran up against - the capacitance, itself. RL On Mon, 19 Apr 2010 08:03:10 -0500, Victor Hernandez <[log in to unmask]> wrote: >RXhwbGFpbiBmdXJ0aGVyICBvbiB0aGlzIG1ldGhvZC90ZWNobmlxdWUuCgpWaWN0b3IsCgotLS0t >LU9yaWdpbmFsIE1lc3NhZ2UtLS0tLQpGcm9tOiBUZWNoTmV0IFttYWlsdG86VGVjaE5ldEBpcGMu >b3JnXSBPbiBCZWhhbGYgT2YgVGVjaG5ldCBMZWdnClNlbnQ6IE1vbmRheSwgQXByaWwgMTksIDIw >MTAgNzo1OCBBTQpUbzogVGVjaE5ldEBJUEMuT1JHClN1YmplY3Q6IFJlOiBbVE5dIEJlc3Qgd2F5 >IHRvIG1lYXN1cmUgImFjdHVhbCIgdGhlbWFsIHBhZCBjb21wcmVzc2lvbgoKUHJvYmFibHkgdG9v >IGxhdGUgdG8gYmUgcmVsZXZhbnQgdG8gdGhlIG9yaWdpbmFsIHBvc3RlciwgYnV0OwoKSWYgdGhl >IGlzc3VlIGlzIGRpc3RhbmNlIGJldHdlZW4gc3VyZmFjZXMgb2YgdGhlIHRoZXJtYWwgaW50ZXJm >YWNlLCB0aGVuIGEKY2FwYWNpdGl2ZSBtZWFzdXJlbWVudCBpcyBwcm9iYWJseSB0aGUgc2ltcGxl >c3QgbWV0aG9kLiBUaGlzIG9mdGVuIGF2b2lkcwp0aGUgcXVlc3Rpb24gb2YgcmVhbCBkaXNzaXBh >dG9yIHN1cmZhY2UgYXJlYSBhcyB3ZWxsLgoKUkwgCgotLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0t >LS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0KVGVjaG5ldCBNYWlsIExpc3QgcHJvdmlkZWQgYXMg >YSBzZXJ2aWNlIGJ5IElQQyB1c2luZyBMSVNUU0VSViAxNS4wClRvIHVuc3Vic2NyaWJlLCBzZW5k >IGEgbWVzc2FnZSB0byBMSVNUU0VSVkBJUEMuT1JHIHdpdGggZm9sbG93aW5nIHRleHQgaW4KdGhl >IEJPRFkgKE5PVCB0aGUgc3ViamVjdCBmaWVsZCk6IFNJR05PRkYgVGVjaG5ldApUbyB0ZW1wb3Jh >cmlseSBoYWx0IG9yIChyZS1zdGFydCkgZGVsaXZlcnkgb2YgVGVjaG5ldCBzZW5kIGUtbWFpbCB0 >byBMaXN0c2VydkBpcGMub3JnOiBTRVQgVGVjaG5ldCBOT01BSUwgb3IgKE1BSUwpClRvIHJlY2Vp >dmUgT05FIG1haWxpbmcgcGVyIGRheSBvZiBhbGwgdGhlIHBvc3RzOiBzZW5kIGUtbWFpbCB0byBM >aXN0c2VydkBpcGMub3JnOiBTRVQgVGVjaG5ldCBEaWdlc3QKU2VhcmNoIHRoZSBhcmNoaXZlcyBv >ZiBwcmV2aW91cyBwb3N0cyBhdDogaHR0cDovL2xpc3RzZXJ2LmlwYy5vcmcvYXJjaGl2ZXMKUGxl >YXNlIHZpc2l0IElQQyB3ZWIgc2l0ZSBodHRwOi8vd3d3LmlwYy5vcmcvY29udGVudHBhZ2UuYXNw >P1BhZ2VpZD00LjMuMTYgZm9yIGFkZGl0aW9uYWwgaW5mb3JtYXRpb24sIG9yIGNvbnRhY3QgS2Vh >Y2ggU2FzYW1vcmkgYXQgc2FzYWtvQGlwYy5vcmcgb3IgODQ3LTYxNS03MTAwIGV4dC4yODE1Ci0t >LS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tCgpfX19f >X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f >X19fX19fX19fClRoaXMgZW1haWwgaGFzIGJlZW4gc2Nhbm5lZCBieSB0aGUgTWVzc2FnZUxhYnMg >RW1haWwgU2VjdXJpdHkgU3lzdGVtLgpGb3IgbW9yZSBpbmZvcm1hdGlvbiBwbGVhc2UgY29udGFj >dCBoZWxwZGVzayBhdCB4Mjk2MCBvciBoZWxwZGVza0BpcGMub3JnIApfX19fX19fX19fX19fX19f >X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fCg== --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------