GB1454301A - Methods and apparatus for measuring and/or controlling the moisture content of a material during a drying process - Google Patents

Abstract

1454301 Measuring relative humidity electrically SIRA INSTITUTE Ltd 27 Feb 1974 [2 March 1973] 10398/74 Heading G1N The relative humidity of a powdered material 3 Fig. 1, in a vessel I with a mesh floor 2, subjected to a drying process by blowing heated air through the floor by a blower 4, is determined by the change in temperature of the material as it dries, measured by a thermocouple 7. The initial, wet temperature signal held in a memory device 10, Fig. 2, is compared at 11 with the current temperature signal after an interval set on a timer 16, the output from comparator 11 corresponding to the initial relative humidity of the material 3. In another embodiment Fig. 3, a wet sheet 20 is fed through a drying chamber 21 and the temperatures of the wet and dried parts of the sheet are measured by thermocouples 24, 26 respectively. The humidity signal may be automatically corrected for the temperature of the hot air, and used to control the drying process.