For example, if the DC voltage range of the MF30 multimeter is 0-1-5-25-100-500V and the dial is marked with 20000 Ω/V, the internal resistance of the 1V range is 20k Ω xl=20k Ω; The internal resistance within the 5V range is 20k Ω x 5=100k Ω, and so on.

1) If two multimeters have the same range but different voltage sensitivities, the one with higher voltage sensitivity will have smaller measurement errors when measuring the same high internal resistance power supply voltage separately.

2) For the same multimeter, the higher the voltage range, the greater the internal resistance, and the smaller the measurement error caused.

In order to reduce the error in measuring high internal resistance power supply voltage, it is sometimes preferable to choose a higher voltage range to increase the internal resistance of the multimeter. Of course, the range should not be too high to avoid increasing reading error due to the small deflection angle of the pointer when measuring low voltage. For low internal resistance power supply voltages (such as 220V AC power supply), a multimeter with lower voltage sensitivity can be selected for measurement. In other words, a high sensitivity multimeter is suitable for electronic measurements, while a low sensitivity multimeter is suitable for electrical measurements.

3) When the internal resistance of the voltage range of the multimeter is more than 100 times greater than the internal resistance of the tested power supply, there is no need to consider the shunt effect of the multimeter on the tested power supply.