What is the function of digitizer?

Answer 1

The same as the function of analog multimeter, but with greater precision and accuracy.

• measure voltage (both DC and AC)
• measure current (both DC and AC)
• measure resistance

Some digital multimeters can also do other things:

• measure capacitance
• measure inductance
• measure frequency
• measure temperature remotely (usually using a thermocouple probe)
• measure current without breaking the circuit (using a clip on magnetic probe)
• test semiconductor devices (diodes, junction transistors, field effect transistors, etc.)
• AF and/or RF signal generator
• etc.