Master the method of reducing detection error when using pointer multimeter to detect DC current

(1) Characteristics of a pointer-type multimeter for detecting DC current. When a pointer-type multimeter is used to detect DC current, since the two probes of the multimeter are connected in series in the circuit being detected, the voltage drop of the multimeter will reduce the equivalent voltage of the circuit, thereby reducing the circuit current, that is, reducing the detected current.

It can be seen that when using a pointer multimeter to detect DC current, the impact of the multimeter voltage drop is closely related to the size of the loop voltage, especially when the loop voltage is low. From the perspective of series resistance, the impact on circuits with high loop resistance is small. In other words, the error when using a pointer multimeter to detect current in a high voltage, high resistance circuit is small and can be ignored; but when detecting current in a low voltage, low resistance circuit, the detection error must be taken into account.

(2) Methods to reduce errors when detecting DC current. When using a pointer multimeter to detect DC current, in order to reduce detection errors, a large current range (that is, low internal resistance) should be used to detect DC current. If necessary, the DC current can be indirectly measured by detecting the voltage across the loop resistor and then calculating it.