The Development of Image Processing Method on the Automatic Reading System of the Glass Thermometer Using a Digital Camera

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.

Studi Pengembangan Sistem Vision Berbasis Kamera Dalam Penentuan Posisi Meniskus Pada Kalibrasi Gelas Ukur

“…Pada tahapan proses segmentasi juga digunakan teknik morfologi opening dan closing [10][11][12]. Teknik morfologi opening digunakan sebagai post-filtering setelah segmentasi awal untuk mengatasi jika masih terdapat artefak pada citra hasil segmentasi.…”

Development of an automatic reading recognition system for liquid-in-glass thermometers based on deep learning

“…In recent years, with the development of computer vision technology, the reading efficiency of LiGTs can be highly improved by developing a visual system [1][2][3][4][5]. Batagelj et al [4] proposed a measurement system of LiGT, which automatically reads temperature by using digital filters to recognize the scale lines of the thermometer.…”

“…On the basis of spatial moment sub-pixel localization, the temperature value is calculated by using location information between edge pixels. Gianto et al [3] proposed to use the HSV color space technology to realize the reading recognition of glass thermometers with the colored liquid. Thresholding and morphological filtering are used to recognize the scale lines to calculate the pixel per temperature unit value (ppt) and segment the liquid column, and the temperature is calculated based on the ppt value.…”

“…Liquid-in-glass thermometers (LiGTs) such as mercury thermometers and alcohol thermometers are widely used in temperature measurement in laboratories and industrial production due to their simple structure and low cost [1][2][3]. Currently, vision techniques [1][2][3][4][5] to improve reading efficiency and accuracy and avoid the error caused by the human-eye reading method. These studies are based on traditional computer vision (TCV) [6] methods (e.g.…”