What kind of switch in place of SW1 will have minimum amount of error in current readings?
Max current is 10 A and we should be able to control the switch digitally.
simulate this circuit – Schematic created using CircuitLab
Electronic – the best way to parallel two shunt resistors using a switch
current measurementshuntvoltage-drop
Best Answer
As guys here pointed out, this may be not the best design idea. First of all, your shunts are of the same value, you will only get twice smaller resistance (there must be a reason, but 10x would kinda make more sense? Depends on your project of course).
You could use a mosfet or even two MOSFETS in parallel (to halve the Rdson) to open a path to the second shunt. Relays have some contact resistance which is greater than that.
Just a random idea that visited my mind: why not to make a current mirror with larger shunt? Of course more components introduce error, there is some small vdrop on the BJT then (bjt current mirrors are more accurate tho in terms of reproducing current). Actually, you can mirror current into two or three circuits with different shunts or just one. Of course, this may and will add to component cost.
If you use current mirror and use some 100R or 10k shunt there or whatever, you can actually use MOSFET to change shunt value because MOSFET's resistance will already be negligible comparing to shunt.
Anyway, this is a random flow of mind, but maybe I'll give you some fresh way to look at your problem.