This charge transfer is due to the mechanical release or closure of the contacts, the contact-to-coil capacitance, and the stray capacitance between signal and relay drive lines.

It is generally unnecessary to verify the isolation capacitance on a switch card, because the capacitance is a mechanical function and should not change over time.

A basic approach to high speed measurements is to minimize stray shunting capacitance through careful mechanical design of the picoammeter.