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FAQ | Tempering
Questions Answers
Why is temperature so important for viscosity measurements? Do I definitely need a thermostat? The viscosity is very dependent on the temperature: A temperature change of 1°C leads to a viscosity change of approx. 5%, depending on the sample. This is why an exact tempering is required for measuring. Standards require an accuracy of tempering of ± 0,02 °C.
Why is a separate control thermometer necessary if the thermostat shows the temperature at 0.01°C? The resolution of the thermostat of 0.01°C does not mean that the absolute temperature of the bath liquid is accurately set to ± 0.01°C. In order to adjust the bath temperature to an accuracy of ± 0.01...0.02°C, control thermometers with a low measuring uncertainty are required. The control thermometers by SI Analytics have a resolution of 1/100°C and can be certified (calibrated).
Why does there have to be counter-cooling when working only slightly above room temperature? An exact regulation of the temperature is only possible, if the thermostat bath is heated and cooled simultaneously. Only if the measured temperate is about 20°C higher than the room temperature, the normal heat loss of the thermostat bath will be sufficient as a counter cooling.
How exactly does the temperature constant need to be in the bath? As per DIN 51562, ISO 3104 and ASTM D 445, the temperature uncertainty must not exceed ±0.02°C.