Digital DC Ammeter circuit

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skilkhan

Joined Nov 8, 2011
9
Hi,
I bought a digital DC ammeter and cannot figure out whether the shunt is already attached with this meter or I have to connect it my self? This is its back image, SHUNT 75 mVDC. If I have to connect Shunt myself, can I use simple resistors as shunt because I cannot found proper shunt at the shop form where I bought it?? Thanks in advance.
IMG0005A.jpg
 

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Hypatia's Protege

Joined Mar 1, 2015
3,228
Re: The markings on the instrument --- FWIW my guess is that the shunt must be such that it drops 75mV at full scale current (IOW think of the un-shunted meter as a 75mV (FS) voltmeter) -- That being the case:

R(shunt)=.075/I(full scale)
While the required minimum power handling capability of the shunt is given by:
P=.00563/R(shunt) -- of course provision of a 'safety margin' is advisable...

A shunt fashioned of a conductor or 'nichrome wire' trimmed for accurate calibration is a good practical approach... Of course said shunt must be of sufficient caliber ('gauge') so as to minimize Δ Temp. over the desired dynamic range of the instrument.

Best regards
HP
 
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