[TCML] The Hammertone Predikter
tcml88 at abelian.org
Wed Jul 1 00:15:44 MDT 2009
> I wanted to check into this...:
> I checked the numbers on all the Pearson current monitors I have
> The numbers don't seem right so either the meter is too weak
> or the internal 50 ohm resistance of the monitors is messing
> everything up.
Yes, the monitor with have a 50 ohm resistor internally across
the output. Makes a mess of any attempt to measure Ls by this
method and you're guaranteed get a low Q.
The Pearson data doesn't give Ls, but we can work it out from
the specified low frequency 3dB point. At that frequency,
XLs = Rs where Rs is the 50 ohm internal load.
Ls = 50/(2*pi*F) ~= 8000/F mH
2100 125Hz 64mH
110 1Hz 8H
101 0.25Hz 32H
411 1Hz 8H
4100 140Hz 57mH
Hmm, these figures might not be correct because that Pearson
web page mentions a 'patented distributed termination' technique.
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