Final control of the cooling capacity of a standard device for calibrating calorimeter rooms is test attained within l/2% using a digital control strategy. There are two control loops in the initialization or start up of the system. One loop sets the position of the valves to get required flow rate using an iteration technique. The second loop adjusts the damper for proper air flow in the chamber.

Accurate measurements of the load on the device is attained using a ratio of flow rates and heat in two temperature equivalent flow paths. A main control loop is used to get an accurate measure of the load. In this loop the power to a small control heater is adjusted to provide a zero temperature difference between two flow streams. A ratio of the power to the small control heater and the two flow rates will give the load removed from the chamber. The control system is flexible over a range of load values.

The control program and system are designed to be user friendly and easy to operate . Requirements for the use of the system are simple electrical and fluid connections described in the program. Following the start of the chiller the user interacts only with the control program. Devices such as valves, rheostats, variacs, and dampers are electrically controlled by the computer. The computer gives a continuous display of temperatures, flow rates, power readings, and cooling load values on the screen. The system also includes data acquisition for later printing or plotting.

Units: Dual