I have been looking at these. I saw one once and it seemed to respond well to noise in a room, such as from lighting. I have been making a noise detector for a while, which has selectable types of noise, electrostatic, magnetic, light, and vibration. I really need to just get one of these and experiment, but the Progressive (now Tempo or Textron or Greenlee ??) probe say inductive while I really thinks its a basic electrostatic probe. I'm thinking of modifying it since its so inexpensive. I don't know if it has any filtering of frequencies in the circuit. Anyone know about these ?
greg