6.5 digit multimeter is the bare minimum for digital work. I recommend a 8.5 for analog.

bullshit. for digital work you only need a 1 digit 7 segment common anode display where segments b and c can be stuck in on position work. the others can be broken. the duality of the binary system guarantees that , if it is 1 it is not zero and vice versa.

segments ba and c are always on. segments a,d,e and f are connected together and go to a wire. touch a logic zero with that wire and segments a,b,c,d,e and f will light showing '0'. leave that wire floating or logic high and only segment b and c will light showing a logic '1'.

there you have it a digital binary logicel level meter using exactly 1 7 segment common anode display and 1 resistor.