Input Impedance of Digital Multimeter
When measuring voltage, the meter should have a high input impedance, so that the current drawn from the circuit under test during the measurement process is very small, it will not affect the working state of the circuit under test or the signal source, and the measurement error can be reduced. For example: the input resistance of the DC voltage range of a 3 1/2-digit handheld digital multimeter is generally 10μΩ. The AC voltage range is affected by the input capacitance, and its input impedance is generally lower than the DC voltage range.
When measuring current, the meter should have a very low input impedance, so that after connecting to the circuit under test, the impact of the meter on the circuit under test can be minimized. Burn out the instrument, please pay attention when using it.
