Look what I scored for just 16 CHF (that's about $16)!!! A proper surface resistivity test kit in working condition. From the dates on the chips it's a late 90's model but for all intents and purposes still good. Let's take a look of what is inside this thing.
I have no idea how this thing works so let's see. The parts I could make out are:
- HCF4066BE - Quad analog switch
- HCF40106BE - Hex Schmitt Trigger
- LPC662IN - 2fA input bias current dual op amp (now we are getting somewhere)
- LPC660IN - same as LPC662 but quad
- BAV45 - Picoampere diode
- BC212L - PNP General Purpose Amplifier
- ZTX450 - NPN silicon planar medium power transistor
- ZTX455 - NPN silicon planar medium power transistor
- TA78L005AP - 5V regulator
As it looks the tester doesn't use any exotic or expensive parts. When I find some time I will try to reverse engineer the PCB and perhaps make a design of my own. We'll see.