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*To*: tesla-at-pupman-dot-com*Subject*: Frequency vs temperature*From*: "Tesla list" <tesla-at-pupman-dot-com>*Date*: Thu, 02 May 2002 19:55:30 -0600*Resent-Date*: Thu, 2 May 2002 19:56:05 -0600*Resent-From*: tesla-at-pupman-dot-com*Resent-Message-ID*: <r6G4PD.A.6kC.z4e08-at-poodle>*Resent-Sender*: tesla-request-at-pupman-dot-com

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net> Terry, Looking over your extensive F, R, and Q data... How much would you expect the Fres to change over temperature... You're looking at tiny fractions of a % for frequency, and it seems to me that dimensional changes in your coil and topload will be on that order... Resistance changes over temperature are going to be significant too.. and that slightly changes the apparent resonant frequency (i.e. it's really not =sqrt(1/LC) but a function of LC and R.. although.. your Q of 200 is high enough that this effect might be small... A quick and dirty Wheeler calculation, while not accurate in absolute terms to hundredths of a percent, could probably give you a sensitivity... that is, L goes as some function (x/(x+1)?) of Length.... and so forth...obviously N isn't changing...but length and diameter certainly are... Likewise, C of topload will also change as a function of temperature (CTE of aluminum is what? 23 ppm/degree... so a 30C change will be a dimensional change of about 700 ppm, and, to a first order, capacitance will change the same (that is, about 0.07%), resulting in a 0.03% frequency change, which is of the same magnitude as you are seeing... The elliptical F vs T curves seem to indicate a thermal/mechanical time lag between parts of the system, that is, some things get bigger and smaller at different rates than other things... This is pretty nifty, in that you can actually make reasonably precise measurements (assuming that the error bars are reasonably sized!)

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