A common task in mixing processes is to measure the product temperature. The reasons for this are manifold. For example, the product temperature must be kept as constant as possible, or it must not exceed a minimum or maximum value. Often, a specific temperature profile has to be maintained during the stirring process For most accurate measuring of the product temperature, it is essential to obtain a representative, actual value.
The positioning of the temperature sensor plays an important role in measuring the product temperature in the stirring tank. As a rule, the temperature sensors are in a fixed position, for example, they have a point of contact with the agitated material through the container floor, the container wall and the container lid. In the case of medium to high-viscosity products in particular, it can be problematic. As a result of different temperatures throughout the stirring tank, it is possible that no representative measure values can be ascertained. Also, the flow field of the stirrer has a significant impact on the local temperature. Furthermore, a difference in temperature between the container wall and container centre may be registered. An improvement can be achieved by using several temperature sensors.
Optimum temperature measures are achieved, when the measuring sensor moves well through the agitated material during the mixing process. This measuring method is used, for example, in planetary agitators. The measuring sensor and a transmitter are integrated on the stirring tool or wall scraper. This ensures optimal heat exchange, and the temperature sensor measures a representative product sample. The transmitter is planted above the product surface and the measured values are transmitted wirelessly to a receiver. The transmitter is operated with a battery which has a lifespan of several years. In addition to the temperature measurement, recording of the the rotational speed, the vacuum, respectively compression, as well as the filling level in the container is often required. The usage of further sensors, for example, for measuring PH value and conductivity are possible. As a measure of the viscosity, the power consumption, respectively the torque of the motor, is sometimes recorded.
Load cells can be used to control the mixer filling and the container discharging process.
In the case of mechanical machine movements, sensors and scanning can enable, for instance, the activation of specific positions.
