humidity sensor

sensor elektor april 1981 — 4-19 Before dealing with the circuit itself, it will be as well to define humidity as such. What is known as the absolute humidity is the number of grammes of water per cubic metre of air at a certain temperature. The absolute or maximum relative humidity is exceeded when the atmosphere absorbs greater quantities of water, thereby becoming saturated or "damp". How much water is absorbed depends on the ambient temperature of the atmosphere. To give an example, hu"living room windows tend to "steam up" ~J 1" "*dky sensor .Somewhat surprisingly pernaps, detecting humidity by electronic means involves a great deal more than meets the eye. In tact, until recently, the few reliable devices that were available were too complex and therefore too expensive for widespread use. The German company, Valvo, recently released details of a capacitive humidity sensor that, inspite of what might be expected from unsophisticated circuitry and low cost, nas many advantag...