To make a 4 point probe in order to test the conductivity of the fibers we've made.
- Make four square or rectangular pieces of palladium foil from a sheet by cutting strips. Make them as small as is reasonable.
- Need to know the area of each strip. The middle two pieces should be as close to the same as possible. The outer pieces are references.
- Cut a small piece of teflon for the strips and wire to go on.
- Put down conductive epoxy for the first lead.
- Put down the first piece of wire on the epoxy, with about 0.5" of wire off the teflon.
- Put down the first piece of foil on top of the wire, using epoxy to make them stick together.
- Repeat for the remaining three leads.
- Note: The pieces of foil should not be allowed to touch each other, and epoxy used for one lead cannot touch another.
Measurements of palladium foil:
- 8.8 x 4.0 mm = 35.2 mm2
- 9.8 x 4.2 mm = 41.16 mm2
- 9.8 x 4.1 mm = 40.18 mm2
- 9.2 x 4.2 mm = 38.46 mm2
Here is a picture of the resulting 4-point probe:
The key advantage of four-terminal sensing is that the separation of current and voltage electrodes eliminates the impedance contribution of the wiring and contact resistances.