Automatic Temperature Compensation (ATC)
ATC - Automatic Temperature Compensation
Temperature is one of the most important factors affecting the accuracy of the measured values. Temperature change significantly affects the refractive index - when the liquid temperature increase its density decrease (the volume of liquid increases, the weight remains naturally the same). Consequently the speed of light in the liquid is increasing what causes a reduction of the measured refractive index.
Optical refractometers use a linear automatic temperature compensation which achieves satisfactorily accurate results and in given temperature range is not therefore necessary to add any corrections. However, the truth is that at the edges of the declared temperature interval the linear compensation achieves the least accurate results. Measure the liquids in steady temperature conditions when the optical refractometer and the measured liquid are sufficiently long in an environment with a stable temperature (the best about 20 °C).
If the refractometer is not equipped with temperature compensation it does not mean that it is any unreliable device. In that case, in an environment with a stable temperature should be not only the refractometer, the measured sample, but also the calibration liquid. At first it is necessary to calibrate the refractometer using the calibration liquid and set "zero" value. Then to measure the sample. If the ambient temperature is changing a lot during the measurement (more than 1 °C), it is recommended to make a recalibration.