Development Of An Automatic Flow Calibration System For Heat Meters

The domestic need for heat meters is increasing daily because of the enforcement of the policy about household heat metering with central heating. As a kind of metering devices, the calibration for heat meters is necessary before they are delivered. However, most of the calibration systems of them are manual which have complex operation, cost a lot of time and calibrated coefficients of heat meters needs artificial adjusting, they make it quite difficult to realize large-scale factory production.Under this circumstance, the automatic flow calibration system for heat meters is developed. It is composed of the circulating water loop in constant temperature, surge tank, solenoid valves, flow regulating valve, electronic scale and control units. Among them, the control units are essential which use the low power TI single chip microcomputer MSP430F149 as the main control chip. They can exchange data with the host computer, control temperature of the constant temperature tank, manage the whole calibration process and write calibrated coefficients into heat meters automatically.The host computer software is designed to provide a friendly man-machine interface for operators, which allows operators to calibrate heat meters quickly and correctly without knowing the inner details of the equipment.The developed system uses weighing method for flow calibration, using electronic scale with high accuracy as the standard gauges to determine the actual flow of the different test points. The developed system can calibrate 12 heat meters in about half an hour without human intervention at the same time, which improves the efficiency greatly comparing with manual systems and avoids human's mistakes as well. The developed system has been produced in practical usage. Large batches of heat meters calibrated by it have been produced, which have all passed the national heat meter standard appraisal and are completely conformed to the national standards.