[Boatanchors] AC Meter Shunt Help]

[Brian Goldsmith]

-----Original Message-----
From: rbethman at comcast.net


Personally, I would NOT use a CT!  They can DEFINITELY be dangerous!

***** So can motor cars!!!

Take a look at VTVMs and DVMs.  They ALL use a hard wire SHUNT to 
achieve their high amp readings.  That's how go from the normal range 
steps, I.E., 200uA, 2000uA, 20mA, and 200mA reading scales to the 10A 
position.

When placed into the 10A position, a solid but tinned copper shunt is 
added to the circuit is placed in the circuit and the meter movements 
ACTUAL full scale is read by the aqcross resistance of the shunt!


*** Pity that the electrical industry does not agree with you,Current
Transformers are universally used to allow heavy currents to be read on
standard low current meter movements since the invention of the alternator
and the transformer.
DVMs are inherently DC operated devices,to read AC they require a rectifier
arrangement which introduces severe non lineararities in the scale
readings.As well,copper has a positive coefficient characteristic of its
electrical resistance,as it heats, the accuracy of the meter reading is
severely flawed.

Are you seriously suggesting that the millions and millions of CT operated
meters and protection devices all over the world be replaced by rectifier
and shunt type meter movements?

The mind boggles!!

Brian Goldsmith.

Bob - N0DGN
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