A shunt is simply a voltage drop measuring device. It can tell you how much current is passing through it from how much voltage drop there is. If you don't pass all current though it, it will show no load., so what you show is wrong. Direction should not matter except you might see (-) instead of (+). I suspenct "smart" shunt just means it has a plug on it instead of terminals, so the direction would be important. You might look at Bogartengineering.com. The Trimetric is a whole lot easier to understand. I am a solar guy who lives off grid. Handybobsolar