For the calorimeter which controls temperature of an adiabatic jacket by injection of hot water, a sampled-data control system is considered as an available method to control the temperature precisely. The control action is accomplished periodically and the opening time of the injection valve for hot water is regulated at every period so that the manipulated variable of the control system can be variable and the superior control law to the on-off control one which is usually used for the hot water method can be applied. In order to prove the availability of this method, the PID control law is applied and its control characteristics is compared with the on-off control system.
The results are as follows. The shorter the sampling period becomes, the smoother the variation of the temperature of the jacket becomes but the longer the time constant of the heating system becomes. Therefore there is the most suitable value for the sampling period and that depends on the equipment of the jacket. The relation between the temperature rise of the jacket and the opening time of the injection valve can be nearly represented by a linear function. The PID control system using this relation and some manipulation on the software can offer better control characteristics than those by usual system. In other words, better control characteristics can be obtained by the periodical control action of the injection valve.