Experiments in temperature measurement and control by microcomputers

The purpose of this paper is to present a laboratory experiment illustrating the concept of feedback control using a microcomputer, as well as basic principles of data acquisition and computer interfacing with sensors and actuators. The experiment consists of an electrically heated, stirred tank of water with a temperature sensor. The heater and sensor are interfaced with an Apple II microcomputer, which may be programmed by the students to record and control the temperature in the tank. Two laboratory exercises in feedback control are described. Enough detail is provided in the paper to duplicate the experiment using off-the-shelf items at a modest cost ($500 excluding the computer and interface cards). The experiment provides an excellent vehicle for reinforcing principles learned in the classroom.