Multimeter showing 0.04V when no power connected

[boylesg]

I have a circuit board soldered up with 6 x dual opamps with a voltage adder on one side and an inverting amplifier on the other.

With no ICs inserted in the sockets and no power connected, my multimeter shows 0.03 - 0.4V or so across those pins of the sockets that are connected directly to resistors and pots.

What is that about? Is this a bit of an artifact generated by the multimeter itself or are the resistors some how generating a small potential difference?

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Ah ha - I thnk just figured out what is probably generating this stray voltage.

It is the zener diode connected to the output of my inverting opamps.

Diodes have capacitance don't they?

 

[HMS1021]

Diodes have capacitance but it is so small the diode's leakage current would quickly discharge it.
There are several reasons you might see a voltage:
1.) Stray RF and line energy that radiates everywhere and is rectified by the meters input or possibly the diode on the board,
2.) The meter has a calibration issue,
3.) Dis-similar metals.
The input load of even a low end meter like a Fluke 115 is 10 megohms, Less than 1 micro watt is enough to produce the voltages you are seeing.