2958 (RP-344) -- A Standard Device for Calibrating Calorimeter Test Rooms — Control System ✓ Most Recent

A computer control system has been developed and analyzed for extremely accurate control of the power to an electric heater to maintain the average temperature difference between two liquid flow streams within ± 0.006 F (0.003°C). the system uses a stepper-motor-controlled variac for coarse control and a stepper-motor-controlled rheostat for fine control. A tight inner loop, based on power measurement, adjusts for power line variation, while the outer loop maintains control of the temperature differential. Control is implemented in a personal computer. Linear and nonlinear analysis and simulation are presented and compared with the performance of the system. The control system is used in a standard device for calibrating calorimeter rooms. The calibration device is able to determine the cooling load to the calorimeter room with ± .5%.

Units: Dual