AN ISOTHERMAL-ENCLOSURE AIR-BATH THERMOSTAT FOR EXPERIMENTAL APPARATUS

Several methods of controlling the supply of power to the heater in a conventional chromotographic oven are compared. The best isothermal pe rformance is obtained when the controller is tuned and the short-term power adjustment is on a time scale comparable to the period of the el ectrical supply. Performance is judged on the basis of baseline noise in sorption-effect chromatography. A novel thermostat consisting of a heated insulated enclosure is described. The power per unit area is un iform so that the temperature of the enclosure is uniform. The perform ance of the prototype isothermal-enclosure air-bath is better than tha t of conventional ovens as judged by the level of baseline noise in so rption-effect chromatography. Ovens of the new design are easily const ructed from readily available components and materials.