Hi Everyone, This is my first post here, so have mercy on me Project: Using a Non-Contact Probe (Sensor) To detect an unknown 1"x1" cube's (it can be steel, alumnium and plastic) Electrical Conductivity (EC) and hence decide its material. Measurement of EC must be in levels of HI MED or LOW Theory to measure EC: Parallel Plate Capacitor with the presence of a dielectric (cube) would change the capacitance C of the parallel plate capacitor. Since Q=CV must remain true always V would change to compensate the change in C It would be a non-contact probe, which means I cannot touch my plates on the cube. Therefore, I could have my plates connected 90degrees on one end ("L" shape) to get as close as possible to any two adjacent sides of the cube. To show HI MED or LOW levels, I would have a comparator which would decide based on pre-determined voltages. Output would be 3 LEDs to display the 3 Levels. Circuit & Implementation: Undecided, and need help here 1. What's the best material to be used for the plates? 2. Do I actually need a circuit to collect charge and form Capacitance or 3. I could provide Vac through the plates and measure any changes in Voltage by placing a cube in between the plates 4. Any other suggestions/comments please? Since it is fairly early stage of design I would still consider any other designs/concept. Most importantly, I would appreciate a circuit diagram with the concept to conduct testing asap. Thanks to everyone reading this post.