Can a Shunt Go Bad?

Ok, sounds like I’m obsessing over nothing again. :R A common occurrence I’m afraid.

I just thought I remembered seeing 0.0 on the display when I flipped the battery disconnect switch to off. The only thing left on the battery when the disconnect switch is off is the Trimetric.

Since I just installed the Redarc DC-DC charger, I thought I must have messed something up.

I appreciate everyone’s response.

:):)

The Trimetric display gets its power from the battery it is monitoring. You can't have zero. You could calibrate it to show zero I suppose. You can get voltage-only from a different battery, not sure how it gets the neg for that B circuit.

I wonder if the leads are just picking up some voltage inductively. What if you ground both sides of the shunt?

They can require calibration which you do by adding a calibrated shunt in series, load it to its rating with a good millivolt meter and tune the shunt.

I see big washers and lugs. Smaller lugs directly on the shunt might change the reading.

I would be more concerned about its accuracy at heavy current.

The specs say ±1 least significant digit.

ScottG wrote:
I've used many shunts over the years and have never seen a failure. About the only thing that could go wrong is if it were vastly overheated and changed its resistance - at least in theory. Never seen it happen but it would be an interesting experiment!

I'd imagine physical damage (do to e.g. a lot of corrosion if exposed to the weather) would be more likely to make one change value. In either case, the damage should be pretty readily apparent to the naked eye.

I've used many shunts over the years and have never seen a failure. About the only thing that could go wrong is if it were vastly overheated and changed its resistance - at least in theory. Never seen it happen but it would be an interesting experiment!

I suspect that's still within the error specification for the unit--and quite possibly the 0.2A would also be within it. Usually the error is plus or minus some percentage plus one (or two or three or however many) least significant digits.

A faulty shunt would not generally cause an offset like this; it would instead cause a more or less constant error by some factor (i.e. it would consistently read 10% more current, or less current) because of changes to the resistance of the shunt. (Bear in mind that a shunt is nothing more than a precision low-value resistor.)

It must take 0.1 amps to show you that 0.1 all lit up :)