[Boatanchors] general OT question on panel meters

[J. Forster]

LOL. It does avoid contact resistance issues w/ low Ohms. In fact, most
all GOOD 50 mV shuntsw are made that way.

I once saw a shunt for 1,000,000 A at the National Magnet Lab...  big
puppy; same design.

Best,

-John

==============


> 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/
>
>