This is an old article from Practical Electronics 1979. It shows the input circuits and digital ranging controls too. Using 7107 chip for display it is an excellent project to build even today. Try it out and improve your troubleshooting skills. – delabs
From Mag – Mains operated multimeter applications in mind,’for both professional/amateur users. The component board and mechanical construction is quite straightforward, and all the components are easily available. Over the past few years,
This particular conception combines many of the functions of high standard professional multimeters with design features including true autoranging, auto-zero, autopolarity, with adequate resolution level and accuracy. Also with good protection, and large l.e.d. display.
The most obvious benefit of autoranging is the fact that much less attention has to be paid to the multimeter by the user in order to get the best possible results. Automatic selection of the range will give the best resolution, and all the user has to do is to select the measurement mode required.