Refitting sensitive galvanometer into ammeter

Pointer ammeters are refitted from sensitive galvanometers. No matter how sensitive the galvanometer is, the current passing through the galvanometer does not exceed 30 microamperes, while the current intensity measured by the galvanometer is 0.6A, or 3a, far beyond the peak value. The ammeter should not only let all the current in the circuit pass through, but also not allow the current through the coil to exceed the safety limit. The ammeter is connected in series with the tested electric appliance, so it needs to be shunted when refitting. The sensitive galvanometer is connected in parallel with a resistor with smaller resistance value, so that most of the current will pass through the resistor and a small part will pass through the meter. Then mark the meter with a new scale.

There is a formula for the resistance value required for refitting: R1 = R / [(I1 / I) - 1], where R1 is the resistance value required for refitting, R is the coil resistance value of the sensitive galvanometer, I1 is the large range of the refitted ammeter, and I is the large range of the sensitive galvanometer.

The ammeter for students has two ranges, that is, two resistors; The range selection of pointer multimeter is actually potentiometer.