Final answer:
A null measurement is more accurate because it does not alter the circuit by introducing extra current or impeding current flow like standard measuring devices do. However, the accuracy is limited by the inherent resistance in connections and temperature-induced resistance changes. Using digital devices sensitive to smaller currents can enhance null measurement precision.
Step-by-step explanation:
A null measurement can be more accurate than one using standard voltmeters and ammeters because it minimizes alteration to the circuit being measured. Standard measurement devices like voltmeters and ammeters introduce an extra current or reduce current flow, which can lead to uncertainties in the measurements. However, with null measurements, voltages are balanced in such a way that there is no current flowing through the measuring device, avoiding any change in the circuit characteristics.
Factors limiting the accuracy of null measurements include the resistance in the wires and connections, which cannot be reduced to zero and can change over time. Temperature variations in resistance can also affect accuracy, although material choice can reduce this effect. Digital devices, which are sensitive to smaller currents than analog devices, can improve the accuracy of null measurements by allowing the measurement of current closer to zero.