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*To*: tesla-at-pupman-dot-com*Subject*: Re: MMC dissipation factor measurement*From*: "Tesla list" <tesla-at-pupman-dot-com>*Date*: Wed, 22 May 2002 07:37:33 -0600*In-Reply-To*: <3CE996CB.9FD73AF4-at-earthlink-dot-net>*References*: <4.1.20020520170523.00a2b3c0-at-pop.dnvr.qwest-dot-net>*Resent-Date*: Wed, 22 May 2002 07:37:42 -0600*Resent-From*: tesla-at-pupman-dot-com*Resent-Message-ID*: <6XkBQC.A.L_C.k8568-at-poodle>*Resent-Sender*: tesla-request-at-pupman-dot-com

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net> Hi Jim, At 05:37 PM 5/20/2002 -0700, you wrote: > >Could one measure dissipation with a calorimeter? > This is how "I" do it. I run 5 amps at 350kHz through it with a thermal couple attached. However, we were wondering if a far more common scope and signal generator could be set up to do it. Thus you would not need the fancy high power signal but just common test equipment. >And, there's a technique where you measure the Q of a tuned circuit with a >swept sine wave... That has possibilities! We are looking for a loss of about 0.05 ohms of resistance in a typical coil MMC. >I think, having looked over the various literature on the RLC meters, that >the best approach will be some form of precision voltage measurement. >Getting 22-24 bit measurements (6-7 digits) is plausible. Using a scope, >with its 10-12 bit A/D, just isn't going to hack it (although, the decrement >measuring approach given in NBS circular is applicable to the scope.. and >there, you are combining 10,000 measurements, so the accuracy should be on >the order of sqrt(10,000)=100 times better than the raw measurement (i.e. 1 >part in 409600... ) Paul's TCMA program's method may overcome this since it calculates Q from all 10000 data points. Small digitizing errors get "cleaned" up by a few orders of magnitude. Paul writes: >Interesting. And you'd want it to be the dissipation at the >TC operating frequency... Yes, dissipation factor varies much with frequency for polypropylene. >Resonate each with a large inductor to the TC frequency >and obtain the two Q values with the pinger and tcma. Use the >difference in Q factor to calculate the extra ESR introduced by the >MMC. This method has two problems: you have to assume the air spaced >cap has negligible loss, and the result depends on measuring the small >difference between two Q factors. This is like measuring Q mentioned above. I wonder if TCMA could measure the Q to a far higher precision than "hand" methods? >And a third method that you could try is to measure that phase angle. >Capture the V and I of the test cap at the TC frequency in some >convenient setup and measure the time delay between the zero crossing >points of the two waveforms. Calibrate out the phase error of the >scope by repeating the measurement again with the roles of the two >Y amplifiers exchanged. This last I think would be the least >accurate with only 10,000 points per sweep. >-- I still have not figured out just how little the phase would be. It is complicated by inductances in the test setup wiring. I note the $10k meters are all four wire probed... That may be a critical thing... Cheers, Terry

**References**:**Re: MMC dissipation factor measurement***From:*"Tesla list" <tesla-at-pupman-dot-com>

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