cellularmitosis:
I looked at ebay, here's a broken one, but it's exactly what we used HP4815A:
http://www.ebay.com/itm/Vector-Impedance-Meter-4815A-RF-Hewlett-Packard-/111671742452?pt=LH_DefaultDomain_0&hash=item1a00278ff4Note the crank handle, this controlled the frequency generator, and the meters, one indicates ohms, the other phase angle. You would crank the frequency up until you find a minima of ohms, and for a cap. any frequency above this was inductive (lead length and internal paths inductance took over). If you get one, make sure it comes with the probe.
The biggest problem in packaging avionics, was to find a way to get the PWB boards ground planes connected with a wide sheet of connection to the box chassis (the infinite sheet conductor in field theory). Screws were sometimes used to multiple standoffs that were pressed into the aluminum chassis. Sometimes we would make clamps from aluminum bars to sandwich a PWB with edge plated, as well EMI gaskets (spring brass with nickel plate).
As both the radiated emission, conducted emission, and then the radiated susceptibility, conducted susceptibility compliance evolved over the years, the ability to make your PWB grounds low inductance to LRU (line replaceable unit) chassis, and to make the LRU mount to the aircraft mounting tray to have extremely low impedance was the game to pass tests.
Susceptibility became a big deal, as airframes went from 100% aluminum, to composite, so test levels of HIRF (high intensity radio/radiate frequency) went from 5 v/meter to 1000s v/m.
Everything became low phosphorus nickel plating between the chassis and PWB. Original plating was just zinc chromate on the aluminum when I started working in 84. Aluminum grows oxide almost immediately, and this is non conductive, hence some sort of conductive plating on aluminum. PWBs use either Nickel or tin lead still.
Note the screws needed to be spaced 20mm minimum (1/4 wave length of max frequencies HIRF was up to 18GHz when I retired), the point being a single screw probably will work with just your single switching circuit, but put a whole high speed processor with lots of parallel address and data buffers all switching at the same time, and you need to have a real good ground connection to prevent the PWB from being an antenna and radiating. As well, if you have noise on your ground, instead of decoupling capacitors quieting the noise, you coupled noise from the ground to the circuit signal (very painful lesson when your out of time, and the emission testing gets worse with every part you add to decouple).
Also the point about a single screw path is an inductor, as all current flows through just this. The larger the diameter, the lower the inductance. So keep this in mind. Multiple in parallel is better.