Negative Ions Detector / Sensor

Posted on Dec 16, 2012

Ions are defined as electrically charged atoms. Positively charged ions have a deficiency of electrons, and negatively charged ions have a surplus of electrons. An ion can also be classified as an atom or molecule with an electrostatic charge. Another classification of an ion is a charged particle that is formed when one or more electrons are taken from or added to a previously neutral atom or molecule. The Ion Detector described in this article can be used to detect the presence of free ions in the air. The Ion Detector, a handheld unit about the size of a pack of cigarettes, is designed to indicate ion emissions from Ion Generators, high-voltage leakage points, static-electricity sources, electric-field gradients, and in other situations where the presence of their relative flux density is required.

Negative Ions Detector / Sensor
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The front cover features, a sensitivity control with on-off switch, a high flux indicator lamp, and a panel meter. An antenna, mounted on the top of the unit, serves an external ion collector. A strip of metallic foil on the outside of the plastic enclosure touches the users hand and is used to ground the unit. For fixed applications, the strip can be replaced by a wire connected to the ground. the Ion Detector--a rather simple circuit consisting of three transistors (two PN2907 PNP, and a single PN2222 NPN type), three resistors, one capacitor, an antenna, a mA meter, and an Led. In that circuit, a telescoping antenna is used as the pickup. In the presence of an ion field, ions accumulate on the antenna, causing a minute negative current to flow to the base of Q1. Capacitor C1 and resistor R1 form an RC network, whose function is to eliminate any rapid fluctuations. Once the negative current becomes large enough, it causes Q1 to turn on, connecting the negative terminal of battery B1 to the base of Q2. That forward biases Q2, causing it to turn on. The detector is set up to detect negative ions. It can be made to detect positive ions by simply reversing the polarity of the transistors that comprise the circuit, i.e., PNP units become NPN units, and NPN transistor is replaced by a PNP unit. I should note that the performance of the detector is seriously affected by high humidity....

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