This is a nice educational reference project based on 89C2051, an 8051 derivative. This uses the Uses analog switches to steer test tones and results. Programmed in assembler to produce pure 1khz tone.
“The example meter that we are demonstrating is typical of many economical digital multimeters that you can purchase, hopefully these instructions will be of some use to you no matter what brand or type of meter you use. ”
A second meter – “Perhaps the most useful hint of the lot is to have a second meter. I personally swear by it – I am constantly measuring voltage and current at the same time, or using one meter for buzzing out a circuit board when the power is off, while the other is set up to monitor voltages in the same board when the power gets turned on.”
Students and Hobbyists can study all the example projects and tutors in this site to become more skillful. They have pages that show how a PCB is made and things like Circuit Design and Prototyping. This Site also happens to be one of the oldest resources in the web for Electronic Embedded Designs.