Re: Random TC Questions- streamer current

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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.