> I'm designing a tool length measurement device for a mill.
> I've settled on the mechanical design which is a tripod arrangement, but
> what I'm after is some contacts to actually make and break the connections.
> I know such beasts exist but I'm having difficulty finding sources for them.
>
> At the moment its looking like I'll have to settle with gold plated PCB
> as the contact material.
>
> I'm looking for gold at the moment because I want to run the contacts at
> a very low current/voltage to minimise arcing.

Be careful with wetting current needs with contacts with very low currents.
Something in hind brain suggests that even gold may not be optimum.
Whether contact is point/area or wiping contact will affect longer
term reliability.

Arcing is less important than energy in arc (intrinsically safe
black-hole beckons).

Normal lore is that anything under about 1 mA is unwise for wetting purposes.
Potential used also relevant - 10V often suggested as useful minimum
voltage for film breakdown but obviously very application dependant.

Use of a combined capacitive/conductive method (shades of SawStop) may
allow zero proximity / low conductivity operation.

Contact sets from other equipment may be useful - eg direct mechanical
operation of contacts from a relay specified for low contact current
operation

.
              Russell
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