Optimized temperature control for rheometer configurations working in separate motor transducer and counter movement mode

This report discusses the performance of the Peltier temperature device for Modular Compact Rheometers (MCR) with an additional lower drive and lower measuring systems with integrated temperature sensor.

Introduction A fast and precise temperature control is of fundamental importance for rheological characterization. It ensures minimal waiting time before starting a rheological measurement, while the precision is necessary for accurate rheological results.

When working with a rheometer setup with two drive units, usually convection temperature devices are used to set the target temperature of measuring systems and samples. One drawback of such systems could be the high air flow necessary for the forced convection, which may affect the torque sensitivity of the rheometer and evaporation of volatile sample components.

In contrast to this, the PTD 180 MD is a temperature device for a rheometer with two drive units in which the sample is heated without the use of forced convection. The desired temperature is applied as shown in Figure 1. The lower part of the measurement system (i.e. the bottom plate or the measuring cup) is located within a heating tube, whose temperature is controlled by an array of Peltier elements.

Due to its specific design it can be used for cone-plate and plate-plate geometries (-20 °C to 180 °C) as well as concentric cylinder and double gap measuring systems (-20 °C to 150 °C) without any modification of the temperature device. The temperature data is read from the lower moving measuring system using a contactless light transmission method based on optoelectronic sensor technology. The optical transfer between the measuring system and rheometer does not influence the torque in the motor. This allows measuring the temperature directly at the sample without affecting the accuracy of the rheometer.

This application report compares the performance of a PTD 180 MD to a convection temperature device suitable for setups involving two drive units. Additionally, it highlights the influence of the location of the temperature sensor, being either within the convection chamber or integrated into the lower measuring system.

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