Last summer I built a current source to power a custom-made pressure sensor. This source uses a REF200 IC and is powered by a wall wart that outputs 5V. The whole circuit is encased in a plastic box that has holes drilled for the energy input (+5V) and energy output (100uA) cables (see circuit).
The circuit worked well for over 7 months and then mysteriously died one day when a friend was using it. He claims he felt a slight shock when he touched a surface that was connected to the pressure sensor. Yeah whatever.
Except that we built another (equivalent) current source and, after a few days of good performance, I felt a slight shock (when I touched a rubber surface connected to the system) and the current source stopped working. Could this shock (which I'm pretty sure is ESD) have damaged the REF200 IC that was inside its own case?
I suppose the charge could have traveled from my hand to the rubber, jumped to the power output (100 uA) cables, then fried the REF200. But I thought that ICs were mostly vulnerable to ESD when not mounted on a board.
So... did ESD fry my defunct current source? And if so, what is a simple way to prevent this? Will grounding the system help? (This is what my friend suggested)