[Boatanchors] general OT question on panel meters

[Al Klase]

HOLY KELVIN CONNECTION, JOHN!

Great technique, thanks.

Al

On 7/9/2013 1:20 PM, J. Forster wrote:
> You run into terminal resistance issues.
>
> If you want to make a shunt, try this:
>
>
> O===o===========o===O
>      |           |
>       ---- M ----
>
> The main current flows through O=========O
>
> The o represent joints, where tge meter leads are soldered to the uncut
> main conductor.
>
> You can get the spacing right by soldering one and using a clip lead for
> thge other. When you find the right point, solder it.
>
> -John
>
> =======================
>
>
>> Ohm's law again.
>>
>> The resistance of the shunt should be 0.05V / 30A = 0.0016666666666667
>> ohms (hard to measure)
>>
>> 50mV is the usual standard voltage drop across a shunt at it's rated
>> current. So a 100 amp shunt won't do it.
>>
>>   From the "COPPER WIRE TABLE" <http://www.w4zt.com/wire/> ,#10 is .9989
>> ohms per 1000 feet.  So cut a piece of #10 copper to 0.001666/.9989 *
>> 1000 = 1.668 feet and use it as the shunt.
>>
>> Somebody check my math,
>> Al
>>
>> On 7/9/2013 11:58 AM, W2HX wrote:
>>> Hello all,
>>>
>>> I purchased a round, analog panel meter 0-30 ADC for a project. Printed
>>> on the face of the meter says "FS=50MVDC" which I take to mean full
>>> scale deflection will occur at 50 mV DC.  Question is, can I get any
>>> 50mV shunt (minimum 30A, of course) and will it work? Or does the shunt
>>> need to somehow be 30A = 50mVDC? If I got a 100A 50mVDC shunt, will this
>>> indicate incorrectly on the meter?
>>>
>>> Thanks in advance for the OT question
>>>
>>>
>>> 73 Eugene W2HX
>>>
>>>
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>> --
>> Al Klase - N3FRQ
>> Jersey City, NJ
>> http://www.skywaves.ar88.net/
>>
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>

-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/