Abstract: A humidity sensor that includes a humidity sensitive material. A sensing circuit associated with the humidity sensitive material estimates the ambient humidity based upon the humidity sensitive material. A heating element is associated with the humidity sensitive material. A temperature circuit increases the temperature proximate the humidity sensitive material and thereafter the sensing circuit estimates the ambient humidity.

Abstract: A humidity sensor that includes a humidity sensitive material. A sensing circuit associated with the humidity sensitive material estimates the ambient humidity based upon the humidity sensitive material. A heating element is associated with the humidity sensitive material. A temperature circuit increases the temperature proximate the humidity sensitive material and thereafter the sensing circuit estimates the ambient humidity.

Abstract: A method and apparatus for measuring the particle concentration of suspensions, especially suspensions having high particle concentration. Light is directed into the suspension, and light scattered by the particles, preferably back-scattered light, is detected at a first and a second position located at different distances from the position where the light is sent into the suspension. The concentration is then calculated asarctanh (E.sub.f /E.sub.n),or preferably ##EQU1## where E.sub.n is the detected light intensity at the first relatively near position and E.sub.f is the light intensity at the second relatively far position. The intensity of the light directed into the suspension is controlled by means of the relation E.sub.f .multidot.E.sub.n =1. The mean value of E.sub.f and E.sub.n is then compared with 1 in order to determine whether the calculated concentration corresponds to the concentration of the suspension being measured.