[Boatanchors] general OT question on panel meters

[W2HX]

great. thanks everyone. I sorta suspected that but now I have confirmation! thanks

 
73 Eugene W2HX
 


-----Original Message-----
From: Bill Carns [mailto:wcarns at austin.rr.com] 
Sent: Tuesday, July 09, 2013 12:15 PM
To: W2HX; boatanchors at mailman.qth.net
Subject: RE: [Boatanchors] general OT question on panel meters

The specification on the shunt (for instance 100A 50 mV) is nothing more than a resistance spec for the shunt. R=E/I  is,  in this case, 50 exp -3 divided by 100 amps = 5 exp -5 ohms or 0.00005 ohms.  So, you see that what you are looking for is a 30A 50 mV shunt or a resistor (Shunt) that is going to produce 50 mV with 30 Amps through it....Bottom line, the 100A 50mV shunt will not work and will result in a meter (for current) that reads very low by a factor of 100/30 or 3.3333...

Bill
N7OTQ

-----Original Message-----
From: boatanchors-bounces at mailman.qth.net
[mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of W2HX
Sent: Tuesday, July 09, 2013 10:59 AM
To: boatanchors at mailman.qth.net
Subject: [Boatanchors] general OT question on panel meters

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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