GB675861A - Improvements in or relating to thermostatically controlled apparatus for testing devices in varying temperature conditions - Google Patents

Abstract

675,861. Testing instruments. SMITH & SONS (ENGLAND), Ltd., S. May 17, 1950 [May 26, 1949], No. 14124/49. Class 106 (ii). [Also in Group XIII] Apparatus for testing indicating instruments in varying temperature conditions comprises an enclosed thermally-insulated space with thermostatically-controlled heating means to maintain an upper extreme temperature in one part and thermostatically-controlled cooling means to maintain a lower extreme temperature in another part thus establishing a continuously varied temperature distribution between these parts with means for supporting instruments under test and for moving them from a region at any temperature to a region at any other between the extremes. The space between the outer and inner walls 1, 2 of an upright cabinet of square cross-section is packed with thermallyinsulating material and a refrigerator 6 attached to the outer wall supplies cold fluid to pipes 5 inside the cabinet near the bottom under the control of a thermostat 7 set, e.g. to maintain a temperature of - 55‹ C. and supplies hot fluid through pipes 9 to pipes 10, 11, respectively, outside and inside the cabinet near the top, the distribution of hot fluid between the pipes 10, 11 being controlled by a valve 12 itself controlled by a thermostat 13. The thermostat 13 is set to maintain a temperature of, e.g., 100‹ C. and also controls the supply of mains current to a heating element 14 to supplement, if necessary, the heat supplied by the fluid. The thickness of the insulation is conveniently graded so that the temperature variation from top to bottom is linear. Trays 17, which can be positioned by chain conveyers 18, accommodate the instruments to be tested which are inserted through a hatch in one side of the cabinet at a height at which the inside and outside temperatures are approximately the same and upper and lower inspection windows are also provided in the same wall. In order to control the humidity conditioned air is supplied through an inlet pipe 19, a corresponding outlet pipe 20 being provided.