Calculating Amps from Millivolts

[Checkthisout]

I have a shunt installed just before my batteries. I have a small standby loaf between 40 and 60 watts and I would like to figure out exactly how much it is.

Using a voltmeter and the shunt, how can I calculate the standby draw?

Yes I could also use the meter itself but that's too easy. I want to to know how to do it longhand.

 

[rmaddy]

W = V x A
A = W / V
V = W / A

 

[Checkthisout]

W = V x A
A = W / V
V = W / A

I don't know the Ohm rating of the shunt.

I guess that means I need to measure it!

CG 500A 75mV Electrical Ammeter DC Current Shunt Resistor Kit,Metal Ampere Current Shunt,Copper DC Shunt Resistance Resistor Kit https://www.amazon.com/dp/B08FJCDTG...t_i_T9WZVXNH3GFV435PC1R3?_encoding=UTF8&psc=1

 

[time2roll]

Need the resistance or rating of the shunt.

I = V/R

You will see 75mV at the full 500 amps for that shunt. Calculates to 150 micro ohms.

If you measure 0.020 volts, divide by 0.00015 ohms, you have 133.33 amps. Need an unusually accurate voltmeter if you are going to measure single amps.

Or you need a different shunt with a lower calibration.

 

[Bud Martin]

So you bought just the shunt without the meter?
Can you show the picture of the shunt?
The location where you put your meter probes on is important.

 

[Checkthisout]

So you bought just the shunt without the meter?
Can you show the picture of the shunt?
The location where you put your meter probes on is important.

Shown in the link above.

It has two screws on either side for the monitor wires.

Intended to install another Tycon monitor but haven't really needed it. Just left the shunt in for future use.