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Re: Random TC Questions- streamer current

Original poster: "Jim Lux" <jimlux@xxxxxxxxxxxxx>

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx> To: <tesla@xxxxxxxxxx> Sent: Saturday, March 19, 2005 11:01 AM Subject: Re: Random TC Questions- streamer current

> Original poster: Ed Phillips <evp@xxxxxxxxxxx> > > "Is it really valid to assume the current in a light globe is the same > for > 50Hz as 100kHz? I would suspect that the "coiled coil" tungsten > filament > may alter this. It might be interesting to compare this to another > method > of current readings such as with a high speed bridge rectifier feeding a > capacitor and a DC ammeter. > Peter" > > Almost certainly, because the Q of the filament is so low that the > reactance probably doesn't count below 1 MHz or so. There are tubes > specifically made for power measurement which consist of two identical > straight filaments mounted in an evacuated envelope. The power to be > measured is fed to one filament and the current in the other adjusted > from a separate source to give equal brightness (the eye is very > sensitive to small brightness differences), at which point the two > powers can be considered equal. I've used a similar method to measure > powers at frequencies as high as 1200 MHz and the accuracy, compared to > a VHF wattmeter, seemed to be within 10% or better.

And the inaccuracies are probably evenly divided between the lightbulb and
the wattmeter, or due to things like mismatch.