Abstract
The reading performance of an analog thermometer, Liquid in Glass Thermometer (LiGT), can be improved using a digital camera. The aim is to minimize the human error on the reading of LiGT and increase the accuracy of temperature measurement results. In order to achieve an accurate result, a robust image processing method is required in the measurement. In this work, the LiGT image generated using a digital camera is analyzed using the technique in HSV color space which consists of some image processing methods (e.g., thresholding, morphology filter). The type of LiGT used is the glass thermometer with the colored liquid. There are three main parts to this developed technique process, i.e., identifying the scale of LiGT to calculate the pixel per temperature unit value (ppt), segmentation of the liquid column, and calculate the temperature based on the ppt value. Through simulation with a synthetic image, we demonstrate that the developed technique in this work has successfully read (measured) the temperature value of the LiGT (having a scale unit of 1oC) with a measurement error of 0.04oC. In the experimental results, we also report the developed technique performed on a real image of LiGT.
Highlights
Glass thermometer/Liquid in Glass Thermometer (LiGT) is an analog temperature measuring instrument, which works based on the principle of the thermometric properties of the liquid column in the glass rod whose volume is proportional to the temperature value [1,2]
As an initial step to test the performance of the developed image processing method, as described in section 2.2, a simulation is carried out using a synthetic LiGT image (FIGURE 3)
In this research, image processing and analysis methods have been developed for scale line reading on an analog temperature measuring instrument, LiGT
Summary
Glass thermometer/Liquid in Glass Thermometer (LiGT) is an analog temperature measuring instrument, which works based on the principle of the thermometric properties of the liquid column in the glass rod whose volume (the liquid column height) is proportional to the temperature value [1,2]. In order to increase readability, the magnification devices, such as a magnifier, can be used to allow interpolation up to smaller-scale divisions [4,6,7,8] Several factors, such as the technician’s ability, the parallax error, and the fatigue on reading, can influence the uncertainty of the reading of the scale on LiGT. This certainly affects the accuracy and the precision of temperature measurement results. The aim is to improve the performance of temperature calibration in terms of simplification of measuring instrument readings and to increase the objectivity of the LiGT reading
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