[GreenKeys] Meter shunt issue...

[Richard Knoppow]

     Measure the resistance of the meter. Since it may be a sensitive 
meter the voltage from an ohm meter may be too much. Put a resistance in 
series with the ohm meter and then measure the difference when the meter 
is in series with it. I would start with a high resistance, say 10K and 
come down in steps until you get close to a full deflection on the meter 
under test. Then measure the value of the series resistor and then the 
total resistance of resistor and test meter. You can determine from that 
the resistance of the meter. You can figure out from that the current 
through the meter at full scale and from that if a shunt is needed and 
its value. Parallel resistors, i.e. a shunt, act for current like series 
resistors do as a voltage divider so you can easily calculate the value 
of the shunt needed for any full scale reading above the sensitivity of 
the meter.
     If you find when using a series resistor on your ohm meter that the 
meter will tolerate the current from the ohm meter you can, of course, 
use it directly.
     I don't like disassembling meters if not necessary, too much chance 
of damaging something.
     DC shunts can be made up using any sort of resistance wire wound up 
on a bit of dowel stock. Even copper is OK if the needed resistance is 
small.

On 5/7/2017 12:09 PM, Kenneth Gartland wrote:
> Hi all...
>
> I am going to dis-assemble the meter again, to have a look
> inside to see if there had been any evidence of the shunt (If any)
> being removed...
>
> As these meters had originally come from from a multiple installation
> on a 19" rack, it is quite possible they had been modified, i.e.
> shunt removed...
>
> Tks agn to all for their valuable input...
>
> Time for me to investigate further...
>
> 73'
>
> Ken
> VE3-HMQ
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL