I need to add a 2-pole switch to the input of an neurological signal amplifier. This is because we want to switch between measuring the neuron signal and sending stimuli to the same needles. We do that now by micro alligators but it is not a good solution because any movement of the wires will effect the tiny needles. Because of risk of external noise I can't hook up the wires to a switch very far away, it must be attached to the tiny amplifier, it is a circular tube 8 mm diameter, about 10 cm long but even touching a mechanical switch attached to the tube will be a problem because of movement. Best would be some sort of relay or transistor switch (SSR) that I can control from a cable. The amplifier has 3 connections to the skin. +, - and reference. I should only need to insert switches to the + and - connections.

So I need suggestions to best solution to make a switch (like a relay or it can be an actual relay) that can switch the small signals. It must be a very small circuit so it can be attached to the 8 mm tube of the amplifier. I intend to attach a small connector to it and place a mechanical control switch on a box elsewhere.

 

You may want to investigate an analog switch such as CD4066 or DG401.

 

I will look into analog switches although I will go for a miniature one. Like MAX4762.

 

This is because we want to switch between measuring the neuron signal and sending stimuli to the same needles

with mechanical swithc your enemies are
probable switching noise
likely long switching delay

alternate
you keep measuring your input at all times -- both for the stimulus and the return -- no switching other than perhaps some input attenuation/(dynamic range adjustment)