5.5 Digit Homebrew DMM

[Marco]

The 34401 is by default autozeroing, one of the mux inputs is connected to 0V and measurements are cycled between it and the input (the assumption being that the leakage current is relatively constant regardless of input selected on the mux).

[sync]

That's a good point. I know that the autozeroing compensate the input amp offset. But with the 100k resistor to ground it also compensate some leakage current. Clever design. Other DMMs just shorts the input amp without a resistor to ground.