A computational scheme to augment the measurement of temperature in internal mixers using multi-sensor probes

High steady state accuracy and a fast response are important requirements for most sensors. In internal mixers temperature is an important variable with respect to automated process control and the resulting quality of output. However, fast sensor response and steady state accuracy is difficult to achieve owing to the strength requirements of probes penetrating the medium, steep temperature gradients, and distributive variations within the batch. The present paper describes a multithermocouple probe technique that is devised to reduce errors and is based on the design of existing probes. Using a simple computational extrapolation technique to process the sensory data on line, it is shown that it is possible to estimate the temperature of the medium rather than that of the probe itself. The technique described is based on laboratory and industrial mixer trials. The latter were carried out using tangential rotor internal mixers, working on rubber compounds. Results show that the method leads to a 50% improvement in accuracy for determining dump temperature. The most accurate performance is achieved under steady running conditions, and the results show that performance is not excessively sensitive to the different formulations tested.