A sensitive detector for static electricity based around a single Field Effect Transistor It can also be used to detect the presence of negative ions, or test a negative ion generator. This circuit utilizes the extra high input impedance of a FET, and also demonstrates the gate terminals sensitivity to changes in voltage. The gate terminal here is left open circuit,connected only to the "probe". The probe is just a few inches of bare copper wire. With no fixed DC biasing, the gate terminal will respond to micro changes in voltage. This causes a current change in the drain circuit and the meter will indicate a charge or "field strength". Static Detector Negative Ion Detector Circuit diagram It is important not to make this circuit on veroboard or PCB material as this will reduce the effective gate impedance. Instead use an "open" construction technique soldering each component together. The probe should not be touched directly and is best insulated in a pla...