Peter Chadwick wrote:
>A lot depends on what the meters are. If the shunt is internal and it's a
>'standard' 100mV meter, then increasing the drop isn't very practical.
Many "1A" meters are actually a 100uA, 1mA or 10mA movement with an
internal shunt. Open the meter and snip the shunt, and you're back on
track.
> A 5x
>overload may not be a brilliant idea for the meter, but it's not normally
>disastrous - or not as much as no protection. A Schottky rectifier across the
>meter gets around the problem
Only partly - remember that the voltage drop at surge currents of 40-50A
will be a lot higher than the rated Vf, for all types of diode.
>(or a pair of them in reverse parallel).
Hmmm... I thought about this long and hard. Can you see any way that a
surge from HV+ to the HV- rail could go in the opposite direction?
>Incidentally, I'm assuming that 100mV is the standard drop for moving coil
>meters in the US.
>
It hardly seems to be a standard anywhere, if it ever was. High-cost
meters (surplus of course) seem to vary considerably, but have a lower
voltage drop than the far eastern imports which typically run 300-400mV.
>Do people still manufacture moving coil meters, by the way, or have electronic
>meters taken over completely?
>
Come on, Peter - they're still in the component catalogues, but good
ones cost a fortune at full price. That's why they're worth protecting.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.com/g3sek
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